Mercruiser 260 idle Temp on muffs??

[johnnyrich10]

ok, just replaced impeller. started the boat in the driveway with the muffs. runs for about five min and the temp hits about 220. and goes pretty much stays there about 220 but every once in a while goes down to 200 and then back up. (this is a rebuilt motor) so is this too high for it to be running on the earmuffs. ran for 10-15 min that way and it did not get any higher.

 

[Icyharp]

Re: Mercruiser 260 idle Temp on muffs??

Whoa way too high, I can't get over 140 for running a half hour in the driveway....check you impeller.

 

[conk3416]

Re: Mercruiser 260 idle Temp on muffs??

Way too high temp. It should run around 140 or 160 max on muffs. Check impeller for proper install. maybe a clog somewhere. or thermostat needs replaced

 

[45Auto]

Re: Mercruiser 260 idle Temp on muffs??

Way too high as others have said. Both my 260's run just below 140 idling forever on muffs.

Were any pieces of the old impellor missing when you replaced it? If so, they may be stuck in the cooling system clogging your flow.

 

[johnnyrich10]

Re: Mercruiser 260 idle Temp on muffs??

I replaced thermostat on rebuild and was running that high before I replaced impeller (which I was hopiong was the cause) I am not sure what the thermostat temp i bought was. but the highest one i see online would be like 195 degrees. I guess i will start looking for a clog somewhere. Where would be the best place to start looking for a clog? Think i should maybe pull thermostat and see which i bought and if its a higher temp one get a lower one? Im a noobie so i am learning as i go. Also is it possible my guage could be off, if so howww do i check that?

 

[johnnyrich10]

Re: Mercruiser 260 idle Temp on muffs??

Way too high as others have said. Both my 260's run just below 140 idling forever on muffs.

Were any pieces of the old impellor missing when you replaced it? If so, they may be stuck in the cooling system clogging your flow.

The impeller itself was in good shape, the water tube was all deformed and there was no water pump face seal.

 

[45Auto]

Re: Mercruiser 260 idle Temp on muffs??

Do you have the Mercruiser manual for your engine? It's Manual #3, 1978-1984 Engines - 4,L6,V8.

If not, post a question asking if anyone has a link to it. There are lots of them you can download free on 4share I believe.

This is the cooling system diagram from it:

Only way I know to verify the gauge is to check it with another one.

Start with the flow test in the manual to make sure you're getting enough water to the engine. If not, your problem is in the drive, a clogged oil cooler, etc.

If the flow test is OK, then your problem is the engine. Make sure your timing is set correctly. Verify that all the hoses are hooked up correctly, it's fairly easy to swap the ones between the manifolds and risers. Make sure the little flow check balls that are in the "T" where the riser hoses connect to the manifold are present and the springs are tight. If they're loose, they'll let your water go out the risers instead of through the engine. I spent a couple of weeks chasing that one down one time.

 

[Doernuth]

Re: Mercruiser 260 idle Temp on muffs??

You probably have the wrong thermostat. Check the manual and get the correct temp thermostat. I am GUESSING based on other posts you need a 140 deg thermostat.

 

[45Auto]

Re: Mercruiser 260 idle Temp on muffs??

The manual specifies a 143 degree thermostat for your motor.

 

[johnnyrich10]

Re: Mercruiser 260 idle Temp on muffs??

Thanks guys i will check all that tonight.

 

[johnnyrich10]

Re: Mercruiser 260 idle Temp on muffs??

Went to autozone at lunch, picked up a 160 thermostat and put it in. (said they didnt have a 140) ran on the muffs for about 30 min and temps stayed between 160-180. think i will pick up a 140 soon and throw it in there. I got the 160 just because i wanted to see if it helped and if that was the problem. Thanks for all the help guys. I am really relieved it was something pretty simple.

 

[45Auto]

Re: Mercruiser 260 idle Temp on muffs??

You need a marine thermostat. The materials in the auto thermostats are designed to run in a closed cooling system (antifreeze with corrosion inhibiters) and will corrode quickly and fry your engine for you in a raw water cooling system. Depending on how often you use the boat, either they'll corrode shut, or the cross strap will corrode and the little pin that the bottom plate pushes against to open will break through the corroded strap. In either case the thermostat won't open and your motor will quickly die. Marine ones are made of brass and stainless steel.

You want something like these:

http://www.summitracing.com/search/...Line/Mallory-Marine-Thermostats/?autoview=sku

Naturally, they'll cost you 3 or 4 times as much as an auto thermostat.