Re-pitching/ replacing prop on Seaweed

[janice142]

My notes when I scrubbed her are as follows:
(F0139) 16 LH 16 on a 1.25 shaft with a 5/16" stainless key
She's a three blade propeller, cannot be larger in diameter (the struts/ cavitation issues would come into play so I'm at maximum diameter)

Today's run under load at the dock shows the pitch is wrong/needs to be less. Mechanic said check online and I went to Vicprop to play with the calculator. Went here: Victoria Propeller, Marine propeller sales, service, and design

Of course now the mechanic and boss are home for the weekend. How would I determine the Number of Shaft Bearings? (I fudged for the calculator and put in 1)

The rest was simple:
Waterline length in feet: 20 feet
Beam at the waterline in feet: 7.5 feet
Hull draft in feet (excluding keel): 2 feet
Vessel weight in pounds: 7000 lbs
Engine Horsepower: 15 HP
Number of engines: 1
Total Engine Horsepower: 15 HP

Engine R.P.M. (max): 2200 RPM
Gear Ratio: 1.9:1
Shaft R.P.M. (max): 1158 RPM

Number of shaft bearings (per shaft): 1
Desired speed in Knots: 6 knots

I don't know how to determine shaft bearings. I know there were some in the transmission when that was put back together.

***********

The problems were thus in today's couple of test runs.
#1) That run with the thermostat in showed (under load) a gradual increase in temperature to 200 degrees where we shut her down. No loss in oil pressure/nothing wrong, but the temperature. The engine exhaust (water flow okay; some periodic smoke -- black, not white, and that only happened maybe three times in the 45 minutes she ran)

a couple or three hours later:
#2) Second run with thermostat out. (there was dripping oil/water at the manifold where the thermostat housing gizmo thingy attaches. According to gauge she went slowly up to 180 degrees and stopped. No further increase in temp.

ALSO, we cannot push the throttle all the way forward with her in gear -- it simply won't go. Out of gear/not under load, there are no issues with throttling up.

There is no tachometer and unlikely to be one. Costs $$ to create the numbers (no mechanical gauge available) and I'm not certain one is necessary. The shop manual says max of 2200 rpm.

Not under load she's a quiet as a mouse.

******************

However, there was/is clanking, vibration under load, and from that the mechanic says "too much pitch" and "engine working too hard" plus "she's burning more fuel than needed". He also said that with a proper propeller that the engine temperature will go down.

So, any thoughts from the pros to mull over this weekend? Any idea how to find out about shaft bearing quantities? The rest of the data is accurate. Well, she weighs a bit less but her fuel tanks are empty.

Thanks.
This engine swapping stuff is like old age: not for sissies! And seriously, thank you for reading to the end of this missive. I'm so ready for this project to be done.

AND, any idea how much (degree of) pitch can be taken out of a prop? Can I go from 16 x 16 to 16 x 10 for instance? (sounds like a lot to me, but wondering)

 

[O C Diver]

Please tell me you aren't doing this test tied to the dock. Maybe I'm reading your post wrong.

Without a tach, you have no idea what RPM the engine is turning in or out of gear.

They're likely referring to the shaft bearing. You have one.

Ted

 

[Vashon_Trawler]

I have a 16" diameter prop as well (16x8). Usually 2" is the max you can re-pitch a prop. You really need a tachometer when testing different props. I went through two before I was happy with the results.

 

[AusCan]

Oooh Janice; We all have different priorities, but a tachometer would be a necessity in my way of thinking. I'd go without a compass before going without a tach.

Why not even pick up a portable handheld rev counter such as this for $15 to measure your shaft speed. Hand Held Tachometer | eBay

 

[FF]

Costs $$ to create the numbers (no mechanical gauge available) and I'm not certain one is necessary. The shop manual says max of 2200 rpm.

No way to know anything with no prop.

If doing this tied to a dock instead of underway almost EVERY engine will be very disteessed.

Your prop is part of the propulsion SYSTEM , and expects the boat to be moving thru the water.

The prop is pitched to work with the boat at 5K or 6K , but NOT at no speed!!!

This is done on large tug boats , but never a yacht.

If your mechanic did not understand this , and allowed the test while stationary , you need a different wrench turner.

 

[Nomad Willy]

Janice is your engine seawater cooled? 200 degrees is fine if fresh water cooled but not if seawater cooled. If you have a seawater cooled engine it would not have a high temp thermostat so your thermostat is defective or you've got a freshwater cooled engine.

FF is right load tests should not be done tied to a float but if your propped right there still shouldn't be black smoke. But FF is probably wrong to say you should fire your wrench. There are things about the situation that FF and the rest of us don't know. Mechanics are good at mechanics but poor at engineering. Go to the engineering side w all the info you have like boat disp, WLL, hull type, prop room, engine, gear ratio ect ect and they he or she should be able to suggest a props blade area, dia and pitch that should give you perfectly acceptable performance for years to come if you don't run at full throttle. Very short periods of full throttle operation should be done to insure that the general health of your engine is good.

Fix the throttle linkage so you can go to full throttle.

Your engine manufacturer may have charts that can predict a good prop.
Information that comes from engineers is best.

There are standards for the length of unsupported shaft between bearings. A wild guess would be probably about 7' max for 1.25 dia. Any prop man should know.

 

[janice142]

These latest two tests were done at the dock -- stern tied so thrust was all forward (no sideways strain possible)

The initial was done underway (when we had the overheat issue/manifold cleared out since, and thermostat replaced)

When I'd asked about making my Teleflex tachometer work and was told "can't happen" ... well, there's obviously been communication disruption. I've ordered one of those indicated above (thanks AusCan) -- and with a step raised can zap the coupler for a reading.

Still, I remember on our 40'er though that after a time you/I knew the rpms because of the sound. Throttle position helped too but sound told the same story. Anyway, my Mother's Day present to me is a handheld tach. This one:
Non Contact Tach Tool Handheld Digital Laser Photo Tachometer Tester RPM Motors | eBay

Last night I did speak with the owner. As OC Diver says, she's got one bearing. The owner also suggested a smaller prop and it looks like Tuesday the diver will be by to swap 'em. Then more testing.

*************

I did re-do the Vic calculator for five knots -- the actual speed I prefer versus hull speed and it tells me:
Speed & Power Calculations

Basic displacement speed and horsepower required
Displacement hull speed (1.34 X sqrt of waterline length): 5.99 Knots
Minimum horsepower required at propeller(s) for Hull speed: 15.3 HP

Calculations based on desired speed and available HP
HP required at propeller(s) for desired 5 knots speed: 8 HP
Estimated maximum speed with existing 15 horsepower:
This is the speed we will use for the propeller size. 6.03 Knots

**********

Throttling back to 8hp used will increase my range though it's all moot so far -- until everything is spot on, I'm not doing the one hour of diesel run. Bob told me I should use about a quart per hour at hull speed. I'm still a bit skeptical but I'll see you on the water, and hopefully NOT at the fuel dock too often.

Thanks for the information.
I may yet survive this engine swap.

 

[janice142]

manyboats: She's raw water cooled.

That's another thing. I'm not thrilled with the idea that salt water could sit in my engine am pondering how to do a fresh water flush at the end of each night underway. The theory is (and stop me if I'm out of line)

Just prior to shutting down (or after she's at temp) take off the top of the Perko raw water strainer, close thru-hull valve, then add fresh water until it's exiting the exhaust. Is there a genius way to tell when that happens? (besides sticking my finger in the water and seeing if it is salty)

Or, is there a better way?
Is this even a good idea?

I know I've read about the process some place but know no one personally who does it. Then again most of my friends own boats that they can afford to replace stuff whereas I've got to make my stuff last for a long time.

Still learning.

 

[Ski in NC]

Janice- which engine is this?

And yep, need to be underway to get good full power rpm numbers.

Eric

 

[janice142]

She's a Volvo MD2 (ancient but functional with all her new parts)
Rated hp 15.5

My tachometer should arrive Tuesday or Wednesday so that's a good thing. On Monday we will see if the diver can come by Tuesday for the prop swap. Apparently there are spares here in the shop so we'll test them first.

I didn't think mine could be pitched down enough -- hearing same from Vashon_Trawler merely confirmed more $ is outgoing. I'm going to try for a swap as I'll be going down in size. We shall see.

When I was discussing this with the owner he indicted he had several in his shop and recommended a 12" (forgot the pitch). He does have a program on his computer to determine size too and recommends that I pick the prop that works for cruising speed versus idle or hull speed. It won't be perfect at high or low end, but will be for the majority of time underway.

And I do know with the gasoline beast I did not sit and idle to charge the batts. If they (batteries) were down the anchor came up and I moved the boat. Didn't have to go far, and might even come back to where I was but when the boat motor was running, I was moving.

Never could figure out folks that idled their engines in place...
I've had a lot of fun taking Seaweed for little mini trips. She's fun to run.

 

[AusCan]

With the handheld tach - You can either use it on the shaft for a direct prop rpm, or on the flywheel for engine rpm, and multiply by your gearbox ratio to calculate prop rpm.

Regarding raw water cooled engines - I've got an old Volvo MD17 which is the daddy of the MD2. I flush it with fresh water only when its going to be sitting for a week or more. If its only a day or two I don't bother. They are very heavy walled and designed to handle the salt water. Besides - Mine already has had salt water in it for 30 years. Its a bit late to keep it pristine.

The main issue is a slow blockage in the exhaust manifold water passages, which requires removal and cleaning with a bit of wire occasionally. When the engine starts running a bit hotter than usual, it's time. Not a big deal.

 

[Nomad Willy]

"fun to run" ..... I like it!!

Don't have much seawater cooling experience but they should be run (from what I hear) way cool (as the kids say) about 140 to 150 degrees or salting of the water jackets will occur.

Smaller prop sounds good and it looks like you're on course . Now that you have a tach I'd be doing as Vashon Trawler suggests. I hate to be subjective but when an engine is properly loaded they sound and feel better. They feel free and at ease. And being propped right will be a bigger advantage to you as you're not overpowered. When you want or need to run her hard you can do it safely and get all the power you have.

 

[janice142]

With the handheld tach - You can either use it on the shaft for a direct prop rpm, or on the flywheel for engine rpm, and multiply by your gearbox ratio to calculate prop rpm.

Regarding raw water cooled engines - I've got an old Volvo MD17 which is the daddy of the MD2. I flush it with fresh water only when its going to be sitting for a week or more. If its only a day or two I don't bother. They are very heavy walled and designed to handle the salt water. Besides - Mine already has had salt water in it for 30 years. Its a bit late to keep it pristine.

The main issue is a slow blockage in the exhaust manifold water passages, which requires removal and cleaning with a bit of wire occasionally. When the engine starts running a bit hotter than usual, it's time. Not a big deal.

Thanks AusCan -- that's good thinking re the fresh water rinse and I'll follow it.

And checking temperature is an easy way to monitor the manifold. A "new" one is $1300 so I'm definitely going to be taking care of this one. She looks great inside. Had three muriatic baths with baking soda neutralization in turn. Now, she's spotless.

I ran water thru all the orifices.

I'd asked about giving her a phospheric acid rinse but was told not to. Our boat was steel (the 40'er) and my dad swore by "green medicine"

Anyway, I'm taking notes and am looking forward to moving the boat south for a spell. Some place with pretty water (am in a river at present and tannin is making my waterline icky)

Plus I'm tied one slip over from a shiny boat. Freshly waxed, the same age as mine, and that Bertram shines I tell you. Bertram owners are almost as rabid as Island Packets, Nordhavns and Hatt's.

 

[jwnall]

Anyway, I'm taking notes and am looking forward to moving the boat south for a spell. Some place with pretty water (am in a river at present and tannin is making my waterline icky)

Pull in to St. Marks for a bit. I'll buy you a beer, and we can swap boating lies. And talk about different TF people.

 

[FF]

The old MD 1 was claimed to be 15HP, the Md 2 was sold as 25 HP and the MD3 was 35 hp.

All used the same cylinders so the ratings were very easy to obtain.

A prop is sized to the boat for about a 50% slip ratio, so if the boat is a 5K boat the prop will expect 5K of water and be pitched for 10K (if there were no slip like a screw in wood).

Unless the prop suffers from marginal blade area the attempt to spin a prop set for 10k of thrust production will alkways overload the engine.

Tied stationary the tiny skinney blades used on sail boats may simply cavitate , which unloads the prop , so no black smoke is seen.

AS an aside we use an MD3B in our 33.3 ft 90/90 which is 28LWL.

It runs on about 13 hp , 3/4 GPH for thousands of hours, so far.

On the AICW it is grand to run to full throttle (only 2300 as we are >overproped< to cruise at 1600-1800) which probably produces 40 hp or so.

With a Maurice Griffiths hull, wide transom , of course the stern sinks as the boat can not climb up on her own bow wave.

This produces a HUGE stern wave , sent as a kiss when one of the imbecile passers is at a long ICW dock.

Great fun as they never believe a tiny sail boat can create a wave that size!!

 

[koliver]

Way too early to be spending $ on repitching.

first, you need to run the boat and see how close your present prop is to being the right pitch. If you are striving for book numbers, your top speed should bring you to 100 -300 rpm below your top rpm with no load.

second, if those numbers indicate the prop is wrong, you need to figure out how far wrong it is. That will take a greater understanding of all of the principles than you have without lots of help, from book theory, a good prop shop's experience, but not likely from a group such as this one.

third, even if you have the wrong prop, if it gives you your proper cruising speed at lower than optimal rpm, there is no harm in keeping it. many of us are intentionally overpropped, so as to cruise at a lower rpm and some some fuel.

fourth, the cries that you will destroy your engine by overpropping are for those who run flat out all the time. If you plan to cruise at 5 to 6 knots, you will see your engine last longer than you will need it. Should you decide to go ahead and re-pitch, your prop shop should be able to tell you how much twist can be added or subtracted from your prop without damaging it or destroying its efficiency. (I added 4" to my 19x13 props to get 19x17. brought my 8 knot cruising rpm down from 2750 to 2000 rpm, at least 5% fuel saving, "Horribly overpropped". This was done in 2004, with no ill effects. I watch for black smoke if I ever go to a much higher rpm and I back off on the throttle if the black smoke appears. There is no chronic overloading with this cautious approach.)

fifth, don't be afraid of an old raw water cooled engine. Those old MD Volvos were designed to operate in a salt water environment, without the aid of a fresh water cooling system. As Eric observed, they should run a little cooler so as to limit the precipitation of salt out of the cooling water, and will go many, many years problem free. (My son recently bought a 30 ft sailboat powered by an old Volvo that is raw water cooled. On mechanical inspection, the 30 yr old engine got a perfect, clean bill of health)

sixth Shaft bearings are out where you can see them. I doubt you have any between the transmission output shaft (that will be the last one in the hidden part of the drive train) and the cutlass bearing in your strut (that will be the one you count).

 

[janice142]

Pull in to St. Marks for a bit. I'll buy you a beer, and we can swap boating lies. And talk about different TF people.

Sounds like fun... our you could bring your Gulfstar out and anchor her by Alligator Point.

Spoke again yesterday with owner of shop doing engine swap. We will use my (incoming) tachometer for readings, comparing with his shop one to make sure the calibrations are identical. I'll learn what is correct.

The diver will come later in the week to do the prop swap.

And I finally ordered an infrared heat sensor gun. I've wanted one since they were $250 (too $$$) but found one on AZ for $20 from the same company that's sending the tach, so popped for it. I should have that tool in my arsenal now that it's come down in price.

And like AusCan suggests, knowing when the temps are creeping up in my manifold will be a good thing to know. This way when I do my engine room checks I'll have some base numbers and places to check.

Because I'm less likely to forget I'll probably paint numbers on the engine -- where to shoot for readings (1, 2, 3, 4, whatever) and will chart it in my logbook. Deviations will be dealt with prior to full-fledged problems developing. And if I paint the numbers I won't forget any.

 

[janice142]

Thank you to all for your input. Props are confusing (my mind doesn't wrap well around slip) but once I've got concrete numbers, then we will proceed. From the vicprop site though, my pitch is w-r-o-n-g.

16x16 when most (tweaking numbers) are calling for 15x10-ish.
The diameter cannot be larger than it is but my pitch is off. But we shall see -- mid-week.

Still, I'm anxious to take my girl away from the dock. There is blue/green water and not far away. I want to be there. Yesterday.

 

[Vashon_Trawler]

Hi, Janice. I look forward to hearing your results! For a trawler, I generally prefer to go with a larger diameter prop and lower pitch rather than a smaller prop and higher pitch to raise RPM. Another words, I like to adjust pitch before I first go down a size. In my case, I recall debating 16x8 or 15x10 and opted for the 16x8. I also cannot go larger than 16".

Let us know how it all goes!

 

[River Cruiser]

One thing I learned during a class on International Harvester diesels was not to operate without a proper thermostat, I think a 140f would be right for a raw water cooled engine in salt water. If they run too high a temp that's when the salt begins to crystallize in the system. The coolant travels thru the system to fast without a thermostat and the engine will have hot spots that can cause internal damage. Good luck and have fun with the new tools.

 

[BruceK]

Really interesting constructive helpful discussion.
Slight hijack, some 4cyl 80hp Ford Lehmans were raw water cooled.

 

[janice142]

Well the results are in: 1900 is Wide Open Throttle

On Thursday I started her right up and ran the figures. She ran nicely for, oh, a half hour or so. No overheating: infrared heat gun showed 95 to 120 degrees, depending where I shot.

But Friday was awful. Nothing would start her. Nothing I tried, and then the mechanic came over and gave it a shot. Finally he went upstairs to talk with the boss who asked the question "has anyone put any fuel in her?"

DUH! She ran for 1/2 hour just with the fuel in her lines and apparently just about the time I shut her down the fuel ran out. Gosh, I felt so blonde!

Anyway, a gallon of diesel, then bleed the engine and she started up like a champ. Same figures -- we are not running her under load (just in neutral at present) and 1900 sounds okay but at 825 or so she purrs.

The figures from vicprop show:
Propeller Size
Number of blades Diameter (inches) Pitch (inches)
3 Blade 16.4 X 11.2

Mechanic suggests 14 x 10 or 16x8.
Anyway, I've got the 16x16LH and that's a common prop (read: cheap to buy, impossible almost to sell) whereas the 16x8 or 14x10's are not inexpensive. He said the best he could come up with was $500. Ouch.

But it's got to be done. I'm going to give it a shot for finding something at a better price. Any ideas of places to check? Used is fine. 3-blade, left hand is perfect.

Thank you for all the advice. She (the Volvo) is a gem... she purrs. With the hatch down and the step closed I can hear conversation and the VHF radio too. I'm excited -- it's nice to be so close to the end of this swap.

I've got a diesel. And my cheeks hurt from smiling so much. Crest toothpaste should give me a retainer for all the grinning I've done!

Oh, and more good news: The shrimp boat next to me is having a fuel truck arrive Monday morning and he's reserved 50 gallons for me. At his price. How cool is that?!?

Life is wonderful afloat!

 

[Larry M]

Maybe give Sailors Exchange in St. Augustine a call. We were in there this morning and they had a pile of used props. You might have to get it cleaned up but you never know.

https://www.sailors-exchange.com/

 

[janice142]

Maybe give Sailors Exchange in St. Augustine a call. We were in there this morning and they had a pile of used props. You might have to get it cleaned up but you never know.

https://www.sailors-exchange.com/

Thanks Larry. Is Sinclaire still there? It's been a while since I was in... (it's a good candy store -- the dock lines were a good price but I didn't need any at the time)

 

[Ski in NC]

Janice- Even with that big prop, if you run around at 1400rpm or below the engine will be happy. If that big old chunk of iron is not making black smoke, it's not overloaded. Love that big old iron...

 

[Northern Spy]

Call vicprop. They have a huge stock of used props that they will repitch for you. They did mine for my repower.

 

[FF]

Well the results are in: 1900 is Wide Open Throttle

Does the boat go fast enough at 1700 or below with no black smoke ?

IF so stick with what you have, and paint a red line at 1700.

My guess is even 1700 will be too much wake , too fast for much economy.

 

[janice142]

Thank you. I've got a list of consignment shops and tomorrow will start calling them. One was found (thanks Steve) for $230, a 14x10 (1" shaft versus my 1.25" tapered) ... That's a great price, if it will work. The guy here will call on that one and any others I can find.

She runs great though -- ran her for a few today before the fuel ran out. I'm smart now. As she'd run for about 15 minutes I called it a day. Tomorrow I'll bleed the system and start the motor again.

And tomorrow I'll fill my port tank. The shrimp boat next to me has ordered 1550 gallons, with 50 designated for me. At his price, that was very nice of him. His boat is steel and yesterday he had a welder up on the bow -- smelled like "home" (when we had our steel 40'er)

I guess I'm weird, but I do own two boats (Seaweed and Algae) so obviously there are some sanity issues. I'm happy though -- and as long as no one appears with a nice jacket with extra long sleeves so I can hug myself, it's all good!

 

[janice142]

Maybe give Sailors Exchange in St. Augustine a call. We were in there this morning and they had a pile of used props. You might have to get it cleaned up but you never know.

https://www.sailors-exchange.com/

I've been on the phone with Bill who works at Sailor's Exchange. There is a 1.125" shaft, 14x10 LH there for just $95. Wonderful price. At this point we don't know if the propeller is good (do you know how to test one?)

Side Note: Sinclair sold the business to Clayton Hansen (who has/had a repair shop nearby) ... and Bill works there.

To test one, apparently you're supposed to hit it with a piece of metal and if it rings, all's well?? I've heard it's called "greening" but anyway, finding out if this one is a-okay is the next step.

$95, plus shipping of course. But thus far, this one is closest. 1.125 is close enough to 1.25 (what I have) so it will work aboard Seaweed. IF it's a good prop.

That's the status as of today 19 May 2014.

 

[Ski in NC]

A 1.125" taper bore prop won't fit on a 1.250" tapered shaft. Prop will need to be bored to 1.250 and keyway broached. Well equipped prop shops can do this with a lathe and broach/bushing.