Running Temp?

[Limited-Time]

00 350 MAG MPI SN 0L671793, seems to run hot 180 to 190 deg.(according to the gage). I plan on checking the engine temp with a IR thermometer to verify gage accuracy. I assume I want to check the temp on the thermostat housing next to the temp sending unit to get the most accurate comparison. Any thoughts. Both the impeller and thermostat were changed at the end of last season. Boat is operated in fresh water only.

 

[Don S]

Re: Running Temp?

Did the housing for the raw water pump look smooth? Not only where the vanes of the impeller ride, but also the back of the pump. It's probably the plastic housing.
Also, being a straight inboard, are you sure the raw water strainer isn't sucking air. Had that happen on the Merc stainers that have just the oring.

 

[Limited-Time]

Re: Running Temp?

Did the housing for the raw water pump look smooth? Not only where the vanes of the impeller ride, but also the back of the pump. It's probably the plastic housing.
Also, being a straight inboard, are you sure the raw water strainer isn't sucking air. Had that happen on the Merc stainers that have just the oring.

I should have stated we replaced the entire pump housing due to the above mentioned issue. As far as "sucking air" that sounds like a distinct possibility. This set up has been hard on impellers since new, kills them in less than 30 hours. And its never turned over with out being on the water. How do I check for air intrusion in the system?? BTW I have the Merc Manual if you care to reference it. Thanks.

 

[Don S]

Re: Running Temp?

I put a piece of clear reinforced hose between the pump and the strainer. Then run it and watch for bubbles (Do this test in the water) make sure all the hose clamps are tight also.

Have a look at the water pickup. I've also seen them come from the factory partially plugged.

 

[Limited-Time]

Re: Running Temp?

Thanks Don. Will try and do the test this weekend. I'll report back what I find. Another question, do you just leave the clear tube in after testing or do you put the original hose back in place?

 

[Don S]

Re: Running Temp?

That depends on the hose you find. If it's a good solid wire wound clear hose that won't collaps, you can leave it. But if it's a nylon reinforced it could collapse, then stick with the original after the test.

 

[Limited-Time]

Re: Running Temp?

Don, I went down to the boat last night for a quick look ai the raw water cooling pump set up. There is no sea water strainer in the system. the line feeding the pump goes directly from the thru hull pick-up to the inlet side of the pump, its a straight shot. I don't know if this matters?? I will still be checking the temp with the IR thermometer later today, if it shows hot I'll replace the inlet hose with a clear line and check for air intrusion.

 

[Limited-Time]

Re: Running Temp?

OK warmed the engine up until the temp gage stabilized at about 180 deg at idle. With the IR thermometer aimed directly at the sending unit, temp. measures 160 deg. The heads check a little hotter, bout 170 deg. Soooooo can I assume the gage is off by 10 to 20 deg???

 

[Don S]

Re: Running Temp?

Soooooo can I assume the gage is off by 10 to 20 deg???

It's either the gauge or the sender. Pull the sender and put it in some hot water at the proper temps for checking.

Water Temperature ----- Ohms Reading
140? F (60? C)------------ 121-147
194? F (90? C) ------------ 47-55
212? F (100? C) ----------- 36-41

 

[Limited-Time]

Re: Running Temp?

Thanks Don, I'll give it a shot and let you know what I find.