Hey, Look! Another overheating problem!!!

[sebago_kid]

I have a 1989 Wellcraft Eclipse with a 5.7L Mercruiser Alpha one, Raw water cooled. I recently ran it on the muffs in the yard, and she purrs like a kitten, and seems to pee a fairly decent stream out the drive leg hole, as well as some spurting water blowing out with the exhaust. At idle (750 RMP) the engine wants to heat to past 200 degrees (and would if I let it go). I give her some throttle, up to about 1800-2000 RPM, and the temp comes back down to 140-150 range fairly quickly. Looking at the T-stat housing, the larger hose on the left is hot, the larger hose on the right, cool as a cuke. When hot (180-plus), the hot hose kinda surges and "jumps" a bit, almost like taking a slug of water, then air, then water... Bad T-stat??? Pump??? I'm wondering if the water pump impeller needs changing as well. This is my first year with this boat, and don't have any history on it... My thought is to change both anyway (t-stat and impeller), but was wondering if anything else might be causing the issue....
any input would be much appreciated!

 

[cooter2506]

Re: Hey, Look! Another overheating problem!!!

Sounds like the impeller in the outdrive.

 

[HT32BSX115]

Re: Hey, Look! Another overheating problem!!!

Thermostats don't fail all that frequently.
Raw water impellers fail frequently. If the previous owner can't tell when it was replaced, replace it. (Look for remnants of previous failures crammed in the t-stat housing and hose from the gimbal)

If the previous owner does tell you he changed it, well, don't believe him and change it anyway!

You can get a kit from any Merc dealer, Napa Auto Parts, or online.

Wait until you get it apart before you get parts. You may need the full kit (impeller, housing, gaskets, plate etc)

If you don't have a service manual, go to the Adults Only Sticky for a download-able manual.


Regards,


Rick

 

[sebago_kid]

Re: Hey, Look! Another overheating problem!!!

Thanks, guys.... that's the way I was leaning.
I guess while I have the drive off, I can check/grease the splines, gimball, and bellows, so it's not a bad thing, I guess.

 

[HT32BSX115]

Re: Hey, Look! Another overheating problem!!!

Good idea!

Mercury suggests going it every couple of years or so....