Repower update

[Finnegus]

After a lot of research and hand wringing we found a great deal on two Cummins 6btas to replace our old Detroit 8.2s. We got the old engines out today and the new were delivered. This is a DIY project with a lot of support from a great yard.
The first step was removing the engine hatch and swim step along with the port rail.
Then I unbolted the detroits and disconnected them. We used a 20 ton fork lift with a 15' boom that reached in the rear door. The engines had to be slid to center line, raised then blocked to shorten the chains. After the disconnect it only took 2.5 hours to lift them out. Total time in getting the detroits out was 12.5 man hours. This included unloading the new Cummins from a trailer. I have more pics but uploading from my phone is a challenge

 

[Comodave]

Very interesting project. Keep the info coming please.

 

[Finnegus]

So the new engines are not at all similar to the old as far as the mounts go. I spent way too much time with paper and pencil trying to figure the mount heights. In the end I built a jig that bolted to the shaft coupler and was pre configured on the actual engines, output coupler and motor mounts. I made this jig to get the mount to stringer heights IRL. Glad I did because I was way off on paper. Welder comes tomorrow to fabricate the mounts.
Nasty surprises in the last two days> The raw water intake and through hulls will have to be replaced. Wrong size and while I could use a reducing coupler, the one I need to do it right is weeks out to order anywhere. I was able to get a new through hull and raw water intake today. It is the right way to do it but add another expense.
The second issue was with the exhaust. While I have 6" pipe between the muffler and discharge, between the motor and muffler is 5". The motor has a 6" mixing elbow. I am just flipping the set up to be 6" all through. The bummer is a suitable reducer to make this work is over $300.00. Not the end of the world but a totally unexpected expense. Hose has also gone up a lot! still inside our budget but YIKES.

 

[Mischief Managed]

Clever use of the jig for the motor mounts!



Please keep posting updates. I have a friend that is considering a re-power from Mercruiser 8.1 gas engines to some used Cummins engines. He's absurdly handy, works on big diesel equipment all the time for his business, and has a ridiculous collection of tools and equipment, so it would be fairly easy work for him compared to most of us.

 

[Finnegus]

Update on mounts

Today was spent removing the pedestals for the engine mounts and cutting them to the height we established using the jig. We expect them to be done welding them by Monday afternoon. Got two done today on site as proof of concept sent the rest to be done in the shop. I was able to get the stubborn exhaust components from an engine shop right up the road. It actually cost less than expected.

 

[IRENE]

Great!!

 

[Finnegus]

Well we are getting closer. The new engines go in on Friday. I got the mounts back from the welder this morning. I also got my props back from the shop and new shaft couplers that match with the ZF transmission. I was sorta suprised by needing couplers as they are the same size as my old ones but the bolt pattern would not match. Luckly my shafts are 1 3/4 so they are fine. I was able to purchase the props from the boat the engines came out of and according to my prop shop they shoud be perfect. I went ahead and had them balanced and cleaned up. Here is a list of things that I needed to do. Some I had planned in advance some were suprises.

1: New sea water strainer (using one from the doner boat). New intake through hull and sea cock.
2: Re work exhust system to consistant 6" from the exhust port to mufflers
3: Replace all sending units on the engines to two station.
4: Connect Cummins Engine Harness to existing harness for gauges and start circut. (This is making my head hurt!) I have newer VDO gauges and really like my dash, plus the harnesses and panels from Cummins would have cost about $6K.
5: New fuel lines from pre filters to engine.
6: New ZF compatable shaft couplers.
7: Custom made attachments for shift and throttle cables.
8: Props
9: Modify engine pedistals
10: Custom engine mounts
Like I said the equiptment is scheduled to place the new Cummins in the boat on Friday morning. It is all looking pretty good at this point. Baring any major hiccups it looks like my cost with parts, props, equiptment, hired labor like welder etc... will come in at just under $10K for the repower plus the cost of the engines of course.

 

[Comodave]

Glad it is coming together for you. Congrats on the progress, keep us up to date as you go.

 

[Finnegus]

Did not budget for this!

Well drilling the new holes for the stringer mounts pretty much sucked! drill got bound up and I broke a couple of fingers.
On the bright side engines are in. Budget line item ER visit $600.00 co-pay Photos of engines in boat to follow.
We had a set back because the batteries being in front of the engines just did not make sense in the long run. They wound up being less that 2 " from the front of motors. it just made a lot of sense to take an hour pause on installing the engines to relocate them to the out board side of the motors. I will be glad I did it when I have to replace the belts or a raw water pump.

 

[ksanders]

Well drilling the new holes for the stringer mounts pretty much sucked! drill got bound up and I broke a couple of fingers.
On the bright side engines are in. Budget line item ER visit $600.00 co-pay Photos of engines in boat to follow.
We had a set back because the batteries being in front of the engines just did not make sense in the long run. They wound up being less that 2 " from the front of motors. it just made a lot of sense to take an hour pause on installing the engines to relocate them to the out board side of the motors. I will be glad I did it when I have to replace the belts or a raw water pump.

ouch!

 

[O C Diver]

While I've never reached that level engagement with my boat projects, I do buy bandages in the economy size. I've spent more time cleaning up spilled blood than I would care to remember.

Ted

 

[SteveK]

The good news is that $600 off the savings of DIY is a bargain, you are still ahead. Heal fast. Thanks for posting the process.

 

[Comodave]

How big is your drill?

 

[Finnegus]

Evidently the drill was too big! The new mounts were perfect though! Got aligned in minutes! Tomorrow we are connecting the fuel lines, electrical and Exhaust. Then I just need to connect the exhaust and build some new battery boxes. Oh and a couple weeks of cleaning!

 

[CharlieO.]

You are making excellent progress on your repower, very impressive!

 

[Mac2]

Are the stringer mounts stainless? If so, there should be a warning label for drilling thick stainless. I almost did the same while drilling 1/2 inch stainless. It catches and comes to a dead stop/torque in a mili second. Home your getting better and thanks for the updates.

 

[Benthic2]

Those right angle handles for drills that everyone leaves in the box come in in handy sometimes! I worked with a guy who was using a Hole Hawg ( very strong drill ) and he one handed it for a minute to adjust his safety glasses and broke 2 bones in his hand.

 

[Mako]

OP what are you doing with the old Detroits - what’s your game plan for selling them?

 

[Sailor of Fortune]

OP what are you doing with the old Detroits - what’s your game plan for selling them?

I think he already sold them. Very nice project...minus the fingers broke

 

[lwarden]

You are going to like those engines, I’ve got a pair in my Lindell and they run great. Also easy to work on and parts are reasonable with good support from SBMAR.

 

[Finnegus]

Latest update, starboard engine is fully installed and got it started today! We blead out the fuel lines and it started in about 10 seconds of cranking. We still have to do the electrical connections on the port and connect the shaft coupler. then swap the old props out for the new. There is a bunch of clean up and a little bilge painting to do and I have to build some new battery boxes as we relocated them. I am aiming to put the boat back in the water by the end of the week. I am hoping that my propeller shop got it right and we don't need to pull out again to have the props re-pitched. It really seems to me based on gut feeling that they are pitched too aggressively. It could be I am wrong... kinda like when I start questioning your gps and nav computer... it is usually right and I am wrong!
After we get the boat back in the water I am going to make two floor hatches to get to the outboard side of the engines. I can get to the outboard side but it is miserable access and inevitably I forget a screwdriver or 10mm socket or....
I also have not connected the hot water heater or red dot heater. I can do those easy enough in the water and hey, its summer! Who needs heat!

 

[Comodave]

You are cranking on the job. Keep up the good work.

 

[Finnegus]

So close!

Got the new props on and just have a few electrical bugs to chase down and some exhaust tinkering before launch on Tuesday. This has been quite a project and I am very glad to see the light at the end of the tunnel. To sum it up.
Engines, Props and other parts. $25,000
Yard Fees and Professional Services $2,500
Misc. Things nuts bolts sealant. $1,500. My time. 120 hours
Helper time 80 hours
I don't think I could have done it any cheaper. Overall pretty happy with how it went.

 

[Comodave]

Impressive job, keep us informed how it goes after the launch.

 

[rslifkin]

That is one quick and impressively inexpensive repower!

 

[Finnegus]

And Thats a Wrap!

As long as the boat was out we went ahead and had the bottom done. Launched at 1:00 PM today. Both motors fired righ up and we ran it up to 1,500 RPM in gear at the dock. No vibration or shimmy. Boat shifted smooth and with the new props about jumped when you engage the trannies. We are taking it back to our slip Saturday so I will post performance info then. The only big glitch is I connected the trannies backwards so my shifters are reversed. Probably a 30 minute fix. Not sure how I managed to do that but of all the things that could go wrong that was a pretty minor screw-up.

 

[Comodave]

Congrats, glad it went so well for you.

 

[Finnegus]

Ran the 27 miles from the yard to my slip today. No issues except a small leak on the raw water side and a stiff shifter on the fly bridge. Perfect day for it! The performance was amazing! My only issue is that my through water speed is too fast at idle. The props seem perfect and the boat jumps onto plane with no lag or jump in rpm once up.
650 RPM idle 4.2 knots
1000 RPM 7.4 knots
1500 RPM 8-9 knots
2000 RPM 12.5 knots
2500 RPM 16.8 knots
3000 RPM 22.7 knots
3150 RPM max 24 knots.
That is 4 knots over the WOT with the detroirs and at any RPM you can have a conversation in a normal voice.
Of course there are critics everywhere. This jerk that lives on the boat across from me thinks I should have put in Cats!

 

[rslifkin]

The high speed at idle is just the nature of the beast if you have a faster boat with engines that aren't really high revving. Big props and deep reductions that give good bite at low speeds also speed things up at idle.

Even with gassers my boat does about the same speed you're seeing at idle. It's just the nature of the beast. Occasionally I end up with just 1 engine in gear if I'm such in a really slow moving crowd in a no wake zone. In marinas it's just in and out of gear when maneuvering or in fairways.

 

[Comodave]

Ask the guy to take a poll and see how many boats have Cummins and how many have Cats. Nothing wrong with Cats but I believe that Cummins would walk away with a numbers in boats comparison.