1987 4.3 litre not warming up

[Evinrude Boater]

This engine will not warm up even when run at 4000 rpm under load. It does get warmer but cools off when slowing down. I thought something might be stuck in the thermostat preventing it from closing so I had a look. There are rust flakes from the housing but nothing in the gap. How much of a gap is there normally when the thermostat is cold?

 

[Alumarine]

I can't tell anything from your picture but the thermostat should close fully.
You can test it in a pot of water.

 

[GA_Boater]

Throw the thermostat in a pot of cool water on the stove and see if it opens as the water heats up. If it opens, take it out of the water and see if it closes as it cools. It should only take seconds.

A thermostat can fail to open and fail to close after opening. When it's closed there is no gap. I think you have a bad one.

 

[Evinrude Boater]

My shop tells me the original is 140 degree and the updated one is 160 degree. Are either acceptable?

 

[Evinrude Boater]

The thermostat remains open about 1/16". I could not see a change when it was sitting in 150 degree water either. It seems to be stuck. What is the safest procedure to remove it. The housing is very rusty and the stainless sleeve is in there tight. Should I press it out from the bottom side?

 

[Scott Danforth]

Replace it. Since you state its stuck, you may need a new spacer sleeve too

 

[Evinrude Boater]

Replace it. Since you state its stuck, you may need a new spacer sleeve too

Do they normally lift out of the housing easily?

 

[Scott Danforth]

yes they do

unless you have a lot of rust and scale in the system

 

[Alumarine]

My shop tells me the original is 140 degree and the updated one is 160 degree. Are either acceptable?

Not usually, if you provide your serial number then the correct thermostat can be determined.
If it's raw water cooled I think it should be 140. If you have a heat exchanger then 160.

 

[Evinrude Boater]

I put a new 140 thermostat in it after sandblasting all the rust out of the housing. It warms up now. Problem solved, thanks for the advice.