Correct Temp

[PullinZ's]

I have a 2006 21i with a Marine Power 5.7 EFI. My temp guage typically runs between 175 and 200 ish. Is this too hot/high?

[hoopykat]

Nope...might be on the higher edge of the normal range, but is OK. Had the impeller changed at all?

-Mike

[whitlock87]

IS your boat set up to use coolant?
What I mean does it run the water from the lake thought the engine, or thought a bundle heat exchanger?
My boat runs off of the lake water, and it runs around 145. Same engine.
I do know that if you are using and heat exchanger, the thermostat is set higher.

As long as it’s not getting any hotter then that, I would nor worry.

[rogersbm82]

I have seen a lot of post lately on running tempature. Thought I would share this. Also this can only be done with EFI engines as if you do this with a carbureted engines it will not adjust the fuel and cause idle problems. Learn this the hard way. If you notice is it hard to find thermostats that are below around 175-180 as 190 being the most popular. When the engine gets heated up they found that there was condensation building up in the vavle covers at the lower tempatures. They have up the running temps to around 190 so that it gets hot enough to burn that condensation off as to not cause corrosion or problems with the oil. I would recomend using the temp that the mannuel says but running around 190-200 is not harmful. Acctually a little better. But like I said this only works on EFI because at the hotter temp. the engine can use less fuel and the computer will adjust for that, the carburetor will not and run too rich and not idle correctly if at all. I know.

[PullinZ's]

Impeller is the original. Boat had 20 hours when I bought it earlier this season. Now has 46 hours, but I wouldn't think the impeller would be bad already. I'm in the river and the water is dirty sometimes. Maybe I sucked something through.

Not heat exchanger. Raw water cooled. If your running at 145 with the same set up, I'm still concerned.

Thanks all.

[dogbert]

Impeller is the original. Boat had 20 hours when I bought it earlier this season. Now has 46 hours, but I wouldn't think the impeller would be bad already. I'm in the river and the water is dirty sometimes. Maybe I sucked something through.

Not heat exchanger. Raw water cooled. If your running at 145 with the same set up, I'm still concerned.

Thanks all.

Impellers last about 2 years. It's actually worse for them if they aren't used because they dry rot. Think of it like a toilet flapper. It's basically the same material. After 2 years, they get brittle and break. I change mine every 2 years and I've still had it go bad on me when I sucked up some debris.

There was a another thread on here where a guy sucked up some debris and it clogged the screen on the transmission cooler. It caused his engine to overheat.

So, I say go ahead and change it...better safe than stranded.

[Timmy!]

My boat runs right at 149 on the digital readout. I hate that you can't have the engine temp displayed anywhere when you are using the cruise control, I like to know what my engine is doing at all times.

[chpthril]

Sounds like it's time for an impeller

[PullinZ's]

good advice. Where's the screen on the transmission cooler? Is that something easy to check?

[R&T Babich]

... If you notice is it hard to find thermostats that are below around 175-180 as 190 being the most popular. ...

Mercruiser states for our engine to run a 160 deg thermostat. Any of the marine supply houses stock it. Our engine runs a solid 170 deg which seems right on for a 160 deg thermostat. It will drift higher, 180 or so, when shut down after a run, but comes right back down to 170. We just got back from Lake Berryessa where it was 112 deg last Tues. and it still ran at 170.

When we got our boat it was 6 years old and had sat for 2 years, so I changed the impeller which was the original (43 hrs). Four of the vanes looked new while 2 of them were cracked at the base, I suspect from sitting in one position for so long. Turning the engine over regularly would not only keep it oiled, but stop the impeller in different positions.

I run a large raw water strainer which has kept out a lot of debris from the cooling system. Our local lake had brush fires above it last year and the lake is covered in fine charred wood. I also run a screen right after the raw water pump to catch any impeller chunks if it ever goes. It's in the pump outlet hose and I can easily check it when changing an impeller.