Problem with oil pressure and temp gauges

[JosieWhales]

Thanks so much for all the information I have reviewed through this forum as a casual browser.
I now have a question that I may find answer to within the weath of knowledge within this forum.
After a full refit of our 1983 Mainship Pilothouse 40 with Twin Perkins our Port side engine runs perfectly but ( isn't there always) as soon as we start and run at idle either from water from a bucket and is always over flowing or on a mooring with sea water. Plenty of water is coming out of the exhaust.
The temp gauge and oil pressure gauge read max or read at proper levels. Starboard side does what's expected and holds true.
We've only ran at idle with concern. And have push throttle easily. I've used a Lazer temp on all parts of both engines (motors) and they have stayed consistent at 190 to 210 ferihieght.
Could this be a ground wire issue that hasn't been found? Would both be connected to same ground?
We really want to take her for a run, but without being able to monitor temp or oil pressure we are very hesitant.
Any clues would be appreciated.
Thanks.

 

[Choices]

Get behind panel and gently pull wires to gauge backs, and retighten
terminals. Same at senders. If doesn't correct swap wires in panel until you find problem. My guess loose connection in panel.

 

[STB]

If you have any variety of the Perkins 4.107, 4.108, 4.236, 4.154, or other "classic" Perkins marine engine, your engines are likely too hot. By my (fallible) memory, the maximum normal operating temperature for all such engines is 197 F, except for the 4.107/4.108, for which it is 200 F and some models of the 6.3544, for which it is 210 F degrees. You'd need to check the operator's handbook to confidently learn the details for your engine. But, based upon my own observation, none of these engines get nearly this hot at idle, even extended idle. Their thermostats open, or start to open, before that and they have a lot of cooling capacity. I wouldn't exact anything to get to 200 F at the slip or after just a little work-out.

This brings me to my next question: Exactly which Perkins model do you have? Can you post the model? Or, better yet, the serial number (which is coded to include the exact model and configuration, called the "build number"). These diagrams may help you to find the serial number: https://shop.perkins.com/support/identify-your-engine

The reason I care about the specific model is because we can start there to figure out the normal operating temperature range for these engines and also because the cooler configuration is very different among the models, and the exhaust and manifold configuration has different forms also. So, knowing the set-up can also help to figure out how to debug this type of issue.

Similarly, I'm not sure what temperature or oil pressure gauges or senders you have. If you can post the model numbers, that would be helpful.

For "american standard" 80psi gauges, as resistance goes up, the oil pressure reading goes down. So, if the gauge is pegged max, there may be a short to ground somewhere between the gauge and the sender. By contrast "american standard" temp gauges read max when open and low temps when shorted, so if the gauge is pegged high, the wire might be broken or disconnected somewhere between the gauge and the sender. Some VDO and "euro" gauges work different. So, it is really important to know what the gauges and senders are. Things can go wrong if a dual station sender is used when there is only one gauge connected, or vice-versa, or a sender using one convention is attached to a gauge expecting another convention.

I was having a little trouble understanding exactly what you are experiencing, so in addition to specifics about the engine, gauges, and senders, it might be helpful to explain, quantitatively, you are observing, e.g. "At start up I read an oil pressure of X psi at my upper helm gauge, Y psi at my lower helm gauge, and Z psi with a mechanical gauge attached to the engine". And, "At startup, I read a temperature of X F at my upper helm gauge, Y F at my lower helm gauge, and Z F when measuring my engine temperature at locations, X, Y, and Z on the block." And then, also, providing the same information after warm-up and at load, with descriptions of the warm-up and load, e.g. RPM, time, and underway or in neutral at slip, etc.

Also, what was involved in a "full refit". This can me anything from a couple of cans of rattle-paint to a full engine and head disassembly, with full machine shop work, and rebuild with a full tear-down and rebuild of all fuel system components and electrical components, and a replacement of all hoses, etc. Knowing what was done may help to understand what could have gone wrong or been missed.

Also, what was the behavior of the system prior to this refit? How has it changed?

 

[Comodave]

I would guess a wiring problem. To quickly verify this you can swap the sender wired between the gauges for the 2 engines. Take the temp sender wire off the port temp gauge and put it on the starboard gauge and vice versa. See if the problem follows the wiring. You could also run a temporary wire over the deck from the sender to the gauge. Also run a ground wire over the deck. See if the gauges work correctly. If they do then it is a wiring problem. Examine the whole wire path for any breaks or bad connections. Maybe even put new connectors on the ends of the wires.

 

[JosieWhales]

After reading advice given, will check connections under panels.
We did trace wires from lower helm to the temp sensor and pressure sensor and found no breaks.
We will look again more thougholly at connectors. I failed to mention that we removed the flybridge for transport and reinstalled at the new location.
We have been doing our diagnostic readings from lower helm believing that the flybridge connects to lower than to motors.
Will check gauge readings from upper this weekend.
Perkins 6.354
Refit# all new thru hulls and backing plates, 1 fuel tank, new radar and chartplotter, transducer. Stuffing boxes changed to pss shaft seals and struts rebeding with new cutlass bearings. New fuel lines.
Will give an update after checking under panels.
Thanks so much.

 

[STB]

Okay. None of those refit items shoukd affect engine temps or pressures.

Note that with analog gauges, upper and lower gauges are not independent. The sender is configured for the load of either one gauge or two gauges. If the upper gauges are disconnected the lower readings will be wrong

 

[Comodave]

Okay. None of those refit items shoukd affect engine temps or pressures.

Note that with analog gauges, upper and lower gauges are not independent. The sender is configured for the load of either one gauge or two gauges. If the upper gauges are disconnected the lower readings will be wrong

You beat me to it. The flybridge changes things a bit. If you do temporary wiring you will need to go to both gauges in order for the sender to work. Different senders for single gauge and dual gauges.

 

[Lepke]

You have 2 engines, one is ok.
Swap the senders between engines and see if the problems moves. If it moves, bad senders. If not, you have a over heat problem.
Another way to verify your gauges is buy 2 mechanical gauges and install where the sender is.

 

[STB]

In wouldn't swap the senders. Why do that? Disconnect the wire and check sender with ohm meter. Check temp with IR gun. See if measured resistance matches measured temperature. Do the same with mechanical.gauge for oil pressure.

 

[Chris Kate]

Greetings all and thank you for all the information available on here. I’m a new1981 Mainship 34 owner with a T6-3544M . Having no oil pressure readings I will thoroughly troubleshoot the wiring mentioned on this thread. Just wanted to ask 2 questions about the senders in these pictures, the top one I assume is temp, the second? Thank you in advance.

 

[STB]

Those both look temperature related to me. They are too high up on the engine to be in the main oil galley and they seem to be near-ish to where the thermostat housing is, so probably near the big part of the cooling path.

Normally, I'd expect one to be the temperature /sender/ for the gauge(s) and the other to be the temperature /switch/ for the alarms.

I see that each had one wire on it. There is the unlikely possibility that, if you have two helms, they are using one sender per helm vs a single dual-gauge model for both.

 

[Chris Kate]

Thank you STB, makes sense to me, two helms (which I have) and /or (gauge and alarm) .Is this the same situation with the oil sensors pictured here: https://photos.app.goo.gl/EzZhpRsnAt1RKynT8

 

[STB]

The picture showing the larger device looks to me.like an oil pressure sender.

The other picture could be the oil pressure switch. I can't quite tell where on the engine it is.

Oil pressure senders tend to be larger to get a good accurate read as pressure changes.

Oil pressure switches can look like that but, more often, they are probably smaller in the same ballpark in size as the temp sender and switch we were discussing.

So, if the smaller of the devices you pictured is in the right place for oil pressure, it is probably the alarm switch.

The oil pressure switch should test to ground (engine block) as a short with the engine off and open once it is running.

The oil pressure sender will vary continuously from small tens of ohms to small hundreds of ohms, depending upon the type, over its pressure range.

 

[STB]

Also, even with two helms you'll need to follow the wiring and test with a meter to know the details. The alarms can be set up in a lot of ways (separate or combined oil and temp alarms, for example)

And upper and lower helm can each have a wire down to the sender or be daisy chained in parallel.

 

[Steve1.0]

Do the gauges go to max when only the ignition is turned to the on position but engine is not started yet?

 

[jgwinks]

If you have any variety of the Perkins 4.107, 4.108, 4.236, 4.154, or other "classic" Perkins marine engine, your engines are likely too hot. By my (fallible) memory, the maximum normal operating temperature for all such engines is 197 F, except for the 4.107/4.108, for which it is 200 F and some models of the 6.3544, for which it is 210 F degrees. You'd need to check the operator's handbook to confidently learn the details for your engine. But, based upon my own observation, none of these engines get nearly this hot at idle, even extended idle. Their thermostats open, or start to open, before that and they have a lot of cooling capacity. I wouldn't exact anything to get to 200 F at the slip or after just a little work-out.

This brings me to my next question: Exactly which Perkins model do you have? Can you post the model? Or, better yet, the serial number (which is coded to include the exact model and configuration, called the "build number"). These diagrams may help you to find the serial number: https://shop.perkins.com/support/identify-your-engine

The reason I care about the specific model is because we can start there to figure out the normal operating temperature range for these engines and also because the cooler configuration is very different among the models, and the exhaust and manifold configuration has different forms also. So, knowing the set-up can also help to figure out how to debug this type of issue.

Similarly, I'm not sure what temperature or oil pressure gauges or senders you have. If you can post the model numbers, that would be helpful.

For "american standard" 80psi gauges, as resistance goes up, the oil pressure reading goes down. So, if the gauge is pegged max, there may be a short to ground somewhere between the gauge and the sender. By contrast "american standard" temp gauges read max when open and low temps when shorted, so if the gauge is pegged high, the wire might be broken or disconnected somewhere between the gauge and the sender. Some VDO and "euro" gauges work different. So, it is really important to know what the gauges and senders are. Things can go wrong if a dual station sender is used when there is only one gauge connected, or vice-versa, or a sender using one convention is attached to a gauge expecting another convention.

I was having a little trouble understanding exactly what you are experiencing, so in addition to specifics about the engine, gauges, and senders, it might be helpful to explain, quantitatively, you are observing, e.g. "At start up I read an oil pressure of X psi at my upper helm gauge, Y psi at my lower helm gauge, and Z psi with a mechanical gauge attached to the engine". And, "At startup, I read a temperature of X F at my upper helm gauge, Y F at my lower helm gauge, and Z F when measuring my engine temperature at locations, X, Y, and Z on the block." And then, also, providing the same information after warm-up and at load, with descriptions of the warm-up and load, e.g. RPM, time, and underway or in neutral at slip, etc.

Also, what was involved in a "full refit". This can me anything from a couple of cans of rattle-paint to a full engine and head disassembly, with full machine shop work, and rebuild with a full tear-down and rebuild of all fuel system components and electrical components, and a replacement of all hoses, etc. Knowing what was done may help to understand what could have gone wrong or been missed.

Also, what was the behavior of the system prior to this refit? How has it changed?

Easy way to tell which way your gauges work is to short the sender terminal to ground with the gauge powered up. It will either peg at min or max. You'll then know if your problem is due to an open circuit or short. Finding the actual fault ain't that easy.

 

[JosieWhales]

Found that both temp sensor and oil pressure sensor had wires ground out somewhere. I ran new wires from gauges to sensors and now can monitor engine. PO had a bunch of splices so just added more spaghetti to the mix. Tested this by bypassing original wires to gauges.

 

[jleonard]

If it were my boat i would put new senders and gauges in a 40 year old boat and be done.