New Tstat, New Impeller - No heat reduction

[ewpvic]

I am stumped. Any ideas?
Where do I start checking in the engine for possible blockage?
1987 3.7 Merc 165

 

[Grub54891]

Tell us what ya have......

 

[500dollar744ti]

Isn't that the one with the crappy 3" heat exchanger that always gets clogged? I'm no expert but I would be looking at the heat exchanger and then manifold/riser.

 

[Bt Doctur]

the riser/res would be a place to start

 

[ewpvic]

Isn't that the one with the crappy 3" heat exchanger that always gets clogged? I'm no expert but I would be looking at the heat exchanger and then manifold/riser.

Yep, but I have the 4". Guess it's time for manifold/riser inspection. Thanks guys. Will report back with new information as it is discovered.

 

[stonyloam]

87 will have a 4" exchanger that almost never gets clogged! Two places to look. Pull the front cover off the exchanger to make sure the tubes are clear. Look at the set of tubes on the starboard (inlet) side, that is where any debris will be (old impeller pieces etc.). Next pull the aft hose off of the exchanger (that goes up to the exhaust elbow) and stick a garden hose in it and turn the water on to see if water flows freely out of the exhaust with little backpressure. If it does not the outlet may be clogged. Is it losing coolant? How hot is it getting? Does the temperature keep going up or stabilize? Might be a good idea to do a compression check, ALWAYS a good idea with a 470. Let us know how you make out.

 

[ewpvic]

Temp rises and falls between 190-200. I believe that is WAY too hot for these engines. Yes? I will check for debris and flow in the exchanger. Thanks stony.

 

[500dollar744ti]

That sounds rather normal for a closed cooling system? What temp is the thermostat you installed?

 

[stonyloam]

Temp rises and falls between 190-200. I believe that is WAY too hot for these engines. Yes? I will check for debris and flow in the exchanger. Thanks stony.

Believe it or not the spec for that engine is 160-205 F, so it is hot but not way too hot yet. should be running in the 160-170 F range. If you still have the old thermostat, try putting it in a pot of water and heating it. Monitor the temp. rise with a thermometer, should start to open at about 160 and be fully open at about 180. If it does then the T-stat was not the problem. Was the impeller housing in good shape, nothing melted? It could be that your gauge is reading high, you might try one of these: http://www.summitracing.com/parts/mrg-2470s/overview/ or a IR thermometer to check. It sounds to me like you have a raw water flow problem.

 

[ewpvic]

Old tstat wasn't opening until it was 180 so I went ahead and replaced it. Impeller housing was in tip top shape. I did go back and notice that there was a small piece of an impeller blade missing. Guess I better find it..............

 

[stonyloam]

Old tstat wasn't opening until it was 180 so I went ahead and replaced it. Impeller housing was in tip top shape. I did go back and notice that there was a small piece of an impeller blade missing. Guess I better find it..............

Look under the front heat exchanger cap, starboard set of tubes, could be it. If it is not there could be in the hose from the impeller pump. There are three sets of tubes the raw water goes back and forth through, so a impeller blade could block enough tubes to reduce the flow.

 

[ewpvic]

OK. Good flow through exhaust. I found the very small piece of impeller. Check the pictures.

 

[ewpvic]

Here are the pics

 

[ewpvic]

Here are the pics

 

[ewpvic]

Oops

 

[Eric 3.7LX Alpha 1]

try and copy paste them in the body of the post, using the attachment link isn't working. Or upload them to photobucket and copy past the link to them.

 

[ktbarrentine]

No pics....

 

[bfjou812]

The manual I have for my 470 which is a 1982 model calls fore a 160 degree thermostat and a 14 psi cap.

 

[ewpvic]

Can you see these?

 

[ewpvic]

Can you see these?