Strange situation

[bud37]

So lets catch up here, stop me if I am wrong.

Do both engines read the same temps at all times, ( NOT overheating ) read by IR temp gun at thermostat housings?

Do both engine temp gauges at both stations read the same ( HIGHER ) temps even at idle, none of which match the engine IR reading ? Previously it seemed the gauges read higher only under load.

Has this been this way since you have owned this boat?

FYI....temp gauges and senders need to match.....previous to you owning this boat things could have been changed creating a mismatch in the resistance range/wiring.

Just to revisit......is it correct that the engines do not overheat under load as checked with the IR temp guns while underway loaded ????

[AlexB]

No oil/transmission coolers have not been changed. And I am not sure what they are. If you can give me a little direction what they look like and where they are I can look into it.

@bud yes both engines read the same temp at the thermostat housing and yes they both read 190 at the gauges.
Without believing the gauges how can I know if the engines overheat? Is there another way to tell?
What do I need to check to make sure everything is aligned so there is no mismatch. Mechanics kind of mentioned that also. They said they believe the gauges are for the temp senders.
Last question for this post. Can you recommend a gauge? I am having problems finding the right one.

Thank you all for your answers.

[km1125]

There's really three issues to consider. Two deal with the temp gages. The temp senders need to match the gages, but they also have to be for a "dual station" setup. You can have the correct sender for a single gage setup, but if you add a second gage you'll get erroneous readings. Having the correct sender for the gage type and for a dual station is what you need.

You can deal with temp gages being off by a bit, as long as you know how much they're off. They don't get more or less accurate when the RPM or load on the engine changes, so if all the sudden you see a big increase, you'll know it's overheating. It'd be really nice if they're accurate too, but not really a 100% requirement. If they really are off by 10 degrees or more, I'd want to resolve that issue though.

The other issue (it appears) is that the readings are changing under load. It wouldn't be unusual in very cold temperature water (usually in the spring) for the engines to run cooler than thermostat temperatures when at idle or very low speeds, but they should come up to thermostat temperature under a moderate load and then not increase much at all when under full load. This is where I become concerned when you noted a 10 degree temp rise just when you went from 2000RPM up to 3500 RPM. That's not even max load, just a moderate increase. I'd really want to see those temp readings done on the engine with an IR gun and if they really do change like that then you probably need to either descale your main heat exchanger or look for debris in something like the oil cooler(s). If you follow the raw water hose from the seacock over to the raw water pump, then from the raw water pump it likely hits the oil cooler(s) before next going to the main heat exchanger. Then, out of the heat exchanger to the exhaust and out the boat. If you posted some various pics of the engines, it would be easy for us to add some circles or pointers to various parts of the engine to identify those things.

[Viper]

Source of the post @ km yes thermostat housing reads 170 gauges 190.

@ viper I am trying to change things one at a time. So far nothing is helping. What approach do you suggest?

That much of a discrepancy between the temp taken at the engine and what's showing at the gauge should be your main focus. Nothing else matters until you discover why and correct that first. Forget about everything else and focus on correcting that metering system. At this point they have changed the sender, so you should have a known good sender at this point. They should know the sender spec that was installed and can hook up a matching gauge AT the engine and record the readings at various loads. This will tell you for sure if the engine is overheating or not. You can then hook up the boat's wiring to the sender and the matched diagnostic gauge to the helm wiring and see if you get the same reading. That will tell you if your wiring is okay. If the readings don't match, you know the issue lies between the engine and the helm.

A good tech will have these tools in his collection for diagnostic purposes. I have a few different whole gauge clusters with a selection of senders in cases that allow me to plug directly to engines to isolate them from the boat's gauges and wiring so I can determine where to focus my efforts.

They should also be able to find out what your gauge spec is and whether it matches your old sender's resistance range for single or dual helm applications. An incorrect match there though would have been obvious when hardware was first change so it would have always been that way. If this is a new symptom, then mismatched gauge and sender spec is likely not the answer.

If after you figure out the the temp reporting discrepancy, and determine that the engine is indeed overheating, then you can worry about finding out why it's indeed overheating but from what you're said so far, I don't know that it actually is so moving on to other pieces of hardware is a waste of time and money at this point.

[throwback2]

Source of the post No oil/transmission coolers have not been changed. And I am not sure what they are. If you can give me a little direction what they look like and where they are I can look into it.

@bud yes both engines read the same temp at the thermostat housing and yes they both read 190 at the gauges.
Without believing the gauges how can I know if the engines overheat? Is there another way to tell?
What do I need to check to make sure everything is aligned so there is no mismatch. Mechanics kind of mentioned that also. They said they believe the gauges are for the temp senders.
Last question for this post. Can you recommend a gauge? I am having problems finding the right one.

Thank you all for your answers.

Oil/trans coolers are usually on the front of the engine. Yours would probably be u shaped with a 1 1/4" hose on either side on top.Pull the hoses off and flush out with a garden hose with nozzle on and see how much crud comes out. It doesn't take much to restrict the flow.