running warmer than it should be.

[jopes]

I have been going over everything trying to figure out why it runs up to 185 or hotter unless I stop driving.

It has a new 160 degree Tstat, and if memory serves me right I seen on iboats it should run no more than 10-15 degrees warmer that the tstat rating.

It runs will not cool down @ idle, it will just hold at that temp, but if I turn the engine off and right back on 2-3 times it will drop back down to 160 degrees fairly fast.

New engine, new manifolds, new tstat, new impeller pump kit.

I have noticed when it is idling in the water it looks like air is passing up the little white tube through the transom from the lower unit.

I read in the shop manual that leakage of air or exhaust into the impeller can cause over heating, but I am trying to under stand how air can leak in there when the lower unit is under water.

 

[Brentathon]

Re: running warmer than it should be.

You sure it's supposed to be a 160 T-stat, instead of a 140?

 

[lcmains1]

Re: running warmer than it should be.

You sure it's supposed to be a 160 T-stat, instead of a 140?

+1, I think that you may need the 140 Stat. Also, How are you checking the temp? I would not rely on the gauge. I was showing low temp on my engine and it turns out the gauge was not even close to the real temp. The infared thermometer for $50.00 really helps

 

[Don S]

Re: running warmer than it should be.

Doesn't matter what thermostat you have 140 or 160, running at 185? is to hot.

Are you sure you have all the hoses for the cooling system on correctly? There has been several with improper hose routing in the past few months.

 

[jopes]

Re: running warmer than it should be.

Hoses are routed properly, I put in the 160 for ttrollling during the summer. Could it be the 160 is to warm due to being at 5000 ft elevation and the lower boiling point of water?


How does that water tube through the transom get air in it along with water when the engine is running?

 

[Brentathon]

Re: running warmer than it should be.

Why would you increase T-stat temp for trolling? I'm just curious.
Over-temping is my biggest fear...so, I always wonder why people have 160's in, when it doesn't seem like Merc switched to 160 until 1995-ish.

You can actually see through the water tube (p/n 32-416721)???
Most people have to temporarily replace their black hoses with clear vinyl to search for air.....that's what I did.

 

[jopes]

Re: running warmer than it should be.

You can actually see through the water tube (p/n 32-416721)???
Most people have to temporarily replace their black hoses with clear vinyl to search for air.....that's what I did.

After a google search on that part number, Yes I can see air / water going through that tube at idle, and when idling in gear.

 

[Doernuth]

Re: running warmer than it should be.

If the boiling point of water is lower, with the temperature of the thermostat being constant wouldn't you want a lower temp thermostat rather than a higher temp???

Put a 140 in it and see if that fixes the temp problem.

As for the air, if your exhaust is through the prop could it be sucking in exhaust gas not air per say? Does it do this in the water or on the hose?

Are you sure the new impeller was installed correctly, if it didn't seal properly it can suck air also....

 

[jopes]

Re: running warmer than it should be.

no it does not suck air on the muffs,

I ordered up a new tstat last night @ 140 degrees, and a new complete pump. For the life of me when I did the pump I can't remember replacing the lower section of the pump.

Wednesday I will be back on the lake with the new parts in the boat and see what happens then.

 

[jopes]

Re: running warmer than it should be.

installed the new Tstat, and complete new impeller kit.

Drove it out on the lake, no air was being sucked in, and I ran it hard today. Gauge was rock solid in holding the temps.

But on a side, note, I think I have other issues that need to be addressed.