Engine overheating issue

[Fury_621]

Hi there,
I'm trying to figure out what's going on with this tem gauge issue. I've got a 1993 OMC 5.7 EFI Cobra with the SX outdrive. Here's what's going on. She'll heat up to about 200 degrees and then at times bounce up to 205-210 then come back down to 200 when we're underway. But at home with the hose hooked up to her she'll stay right at 160. Now with that said.........I've researched all the forums for answers. Here's what I've done. On the outdrive I replaced the impeller, installed a new gasket and the housing and made sure there were no air leaks around the impeller housing. Still does it. So I replaced the thermostat with a brand new 160 degree one from iboats, still does it. So one day we ran the boat up river for about 8 miles and I checked the risers on the engine and I could hold my hands on them without flinching. They weren't hot. So then I went and checked all the hoses and tightened some clamps and back flushed the motor, still no effect on the temp reading. The only thing I haven't checked or fooled with is the screen over the intake in the lower unit on the outdrive or the gauge itself. I've kinda gotten used to keeping one eye on the river and one on the temp gauge. I installed captains call exhaust this past summer and noticed that now it doesn't do it as frequently but yet it still does it. Any suggestions/ideas ????

Thanks for any help

Ps, raw water cooling system and the boat was originally from Florida and in saltwater for how long I don't really know.

 

[Scott Danforth]

first, welcome aboard

use an IR thermostat to verify the reading. if you can hold your hand over the risers, they are under 180

Is the motor itself warm to the touch? the exhaust manis and risers are always getting water flow. however it sounds like you may have a blockage in the t-stat housing. I would back-flush the motor and lines. debris could be plugging up the T-stat housing

 

[Fury_621]

Thanks........I'll give that a try when it's warm enough outside. I never felt the motor itself for temperature. Just the risers as I read online somewhere that if you can touch them and keep your hand there then that indicates that you've got good flow. I'm not a rookie, nor an expert but what is the T stat housing. I think I know. Is it behind the engine that a single line comes from the outdrive then t's to the motor

 

[Fury_621]

Duuuh........your referring to the thermostat housing. If so, I've already removed that and looked at it and replaced the thermostat

 

[HT32BSX115]

Duuuh........your referring to the thermostat housing. If so, I've already removed that and looked at it and replaced the thermostat

Howdy,


He meant to get yourself one of those Infrared Harbor Freight (or equiv) temp "guns".

Point it directly at the T-stat housing to verify that your gage is accurate. Your gage might just be way off.

You can also determine your block, manifold and riser temps too....

If the engine is absolutely overheating,

It's either due to cooling water flow (restricted coming IN or getting out), clogged block, heads, risers, manifolds etc or there's blockage from previous raw water impeller failures (pump fragments) that are clogging cooling hoses or an oil/PS cooler etc.

Regards,


Rick

 

[3ronny3]

Don't forget to cneck the power steering cooler I spent many hours and money to find it was blocked.

 

[Scott Danforth]

the power steering cooler is usually the first "strainer" in the system.