Strange situation

[AlexB]

Hi Everyone
I am somewhat new to boating. Had my carver for about a year.
Couple of weeks back I noticed that both of my engines under load got up to 190 degrees. To me that seems high, I read at those temperatures sea water separates and could clog risers and manifolds. Spoke to the mechanics at the marina and they said they put an IR gun on the thermostat housing and it showed 165. They think it’s the temperature senders. Problem is I don’t remember what the temperature was when I got the boat.
Any insights from this community would welcomed.
I have a 92 carver 33 with crusaders 454.
Thank you in advance.

[buster53]

First thing that comes to mind is your bottom and especially your running gear has picked up barnacle growth. That will easily kill speed and put extra strain on your engines pushing the heat gauge up.

Especially since it is happening to both engines, fouled bottom is the first thing I’d look at.

[Viper]

If they shot 165 deg at the stat housing (I prefer the sender itself) at the same time that the gauges indicated 190, then the engines are running much cooler than the gauges are indicating. That could be due to a few things like bad senders, gauges, poor wire connections, (check your grounds), harness connectors, etc. Are these raw water cooled or fresh water cooled (uses engine coolant)?

[AlexB]

The engines are FWC.
How do I check if I picked up barnacles? Do I need to get the boat out of the water?
What should the temperature gauge be showing? I read that 175 is a good temp for these engines.

[buster53]

The engines are FWC.
How do I check if I picked up barnacles? Do I need to get the boat out of the water?
What should the temperature gauge be showing? I read that 175 is a good temp for these engines.

All depends on what thermostat you have installed. 175 is a good temp for FWC engines.
If you are in salt or brackish water, you have barnacles. You have 2 choices, either haul the boat for cleaning or hire a diver to do it. When was the last time the boat was out of the water and bottom painted?

[AlexB]

It was on shore this winter. Bottom was painted in April

[AlexB]

How can I check true temperature of the engine?
I have an IR gun just not sure where to point it.

Thanks for all your responses.

[bud37]

If you want to check the sender accuracy, point the laser at the base of the sending unit itself.....there will always be a slight difference, cooler on the outside. Try different areas around the engine, cylinder heads front and back......the block itself near the casting plugs, the water pump housing and the engine coolant hoses.

Those laser temp/IR guns are great for troubleshooting and quick checks while running but be sure to be fairly close, also they are not that accurate shooting shiny objects is what I have found.

[km1125]

Pick yourself up an IR thermometer. You'll use it for a LOT of things once you get it and they are pretty inexpensive.

You need to compare the thermostat housing temps to the gauges at the same time. No (real) way of knowing what the comparison was if someone else just told you they took a reading and what they read on the gauges (if they even did). You need to have an idea how accurate (or not) the gauges are. It's OK if they're off a bit, you just should be aware of it.

It's entirely possible that you don't have enough cooling water flow through the system and that's why the temps climb under load. The gauges don't get less accurate, so if you're reading reasonable temps while underway but get higher temps when at higher speeds/loads that's telling you something is wrong. That could be some impellers that need to be replacing, or that you have some obstructions in either your heat exchanger or in the exhaust where the cooling water dumps in. How many hours are on the engines? Have they always been in salt? When was the last time the impellers were changed? How about the risers or elbows?

[AlexB]

The boat is in salt water. The risers and manifolds were changed in 2018. The engines have 650 hours on them. What is confusing me is that both gages show the same temp. I would think that if there was a clogging issue it would be one engines not both at the same time and same temp.
I will be on the boat this weekend I will measure temps all around the engine.