engine temp 5.7 MPI

[sgwill122]

Just installed a new 2012 5.7 MPI Indmar with full closed cooling(heat exchanger). The engine came fully assembled ready to go including anti-freeze and oil. I have ten hours on it and am a little concerned that the engine is running too cool. It runs 145 to 150 degrees on the temp gauge which I verified with a heat gun. I have read many posts here and it seems that 140 degree thermostats are used on raw water cooled engines in saltwater to prevent salt buildup in the manifolds but that an engine with closed cooling should use a 160 degree thermostat as the engine is more efficient hotter. The place I bought the motor from says the lower temps are good with no real explanation but the engine manual calls out a 160 degree T-stat. So my question is should I swap out for the higher thermostat(I am not looking to make unnecessary changes)? I have a couple car buddies that claim there is little gain by running hotter since it is injected and the computer adjust the fuel accordingly.

 

[Don S]

Re: engine temp 5.7 MPI

You need the 160? thermostat with a closed cooling system.

 

[HT32BSX115]

Re: engine temp 5.7 MPI

I have a couple car buddies that claim there is little gain by running hotter since it is injected and the computer adjust the fuel accordingly.

As is usual, the car buddies don't know what they're taking about.

Running an EFI marine engine too cold will make the ECM operate the engine in a "warm-up" mode. I.E. it'll run too rich.

You need to ensure that it has the correct (160?) stat. My closed cooled engine runs from 160-180?F with a 160? stat.

 

[hottoddie]

Re: engine temp 5.7 MPI

As is usual, the car buddies don't know what they're taking about.

Running an EFI marine engine too cold will make the ECM operate the engine in a "warm-up" mode. I.E. it'll run too rich.

You need to ensure that it has the correct (160?) stat. My closed cooled engine runs from 160-180?F with a 160? stat.

This is 100% correct. Change to 160* and the engine will run better and use less fuel.

 

[sgwill122]

Re: engine temp 5.7 MPI

It's unaminous time to change the thermostat. I was already impressed with the engine so far. Next question. I have an old spare 160 degree thermostat I had for my previous engine, is there any reason I cannot use it assuming it fits? No one local carries Indmar specific parts.

 

[sgwill122]

Re: engine temp 5.7 MPI

Replaced the 140 with a standard 160 and drilled a 1/8th inch hole. Engine now stays at 178. I think I am now finished.