1995 Evinrude 90hp overheating???

[renegade15]

This is an 1995 E90SLEOC on a 17' center console. Had the boat out last night for fireworks and when going through a long no wake zone I noticed the temp start to climb on the temp gauge, up to about 180 at idle. I know gauges aren't alway the most trustworthy things on a boat so I pulled the cowl off and touched the heads for the 3-4 seconds to "ouch" test and got about 2 seconds...I know, not scientific but just wanted to make sure they were even and not rediculously hot already. Anyhow, there is a good stream coming from the tell tale and the waterpump was done in march. Thermostats were done last year when the powerhead was rebuilt. I idled to a go fast zone and cautiously gave it throttle and the t-stat bypass kicked in and the motor cooled off right away back down to the 150-ish area. My question is does this sound like thermostats...oddly enough both of them? Or something else? I read in another post about exhaust housing gaskets allowing hot water/air to mix with the intake of cool water and running the temp up, but it seems like that would have kept the temp high all the time no? We got back too late for me to troubleshoot anything last night without waking the neighbors, will grab my temp gun and explore some tonight, just wanted to throw it out there though to get diag started.
Thanks!

 

[barryvj]

Re: 1995 Evinrude 90hp overheating???

I have the same engine, same year. If I idle for more than 5 mins or sometimes when in no-wake zones, I overheat. This is particularly concerning, because I rebuilt the engine two years ago for severely scored cylinders on the 1-3 bank. Since then, I've replaced both t-stats and put in a new waterpump, but it still happens. I'm very curious as to the resolution...I'll stay tuned.

 

[bigheaded5]

Re: 1995 Evinrude 90hp overheating???

Im in no way an expert.... I had a problem that sounds very similar and found the solution here a few days ago myself. My boat ran great at plane but idle speed for a few min, the high temp alarm sounded. turned out, one of my stats was stuck OPEN and the other stuck CLOSED. i tested them in a pot of boiling water..no change in either. Replaced them and problem solved. Turns out theres another valve(s) called a pressure relief valve that operates at higher rps(pressure) and bypasses the stats and cools the heads at high speed. the stats will stop water flow at low speed if its bad (stuck closed). hope this helps.

 

[fishfeatures]

Re: 1995 Evinrude 90hp overheating???

is the motor used is salt water?
The reason I ask is that I saw a motor last month with the same issue and when we took it apart we discovered that the PO ran it in salt water and never flushed the motor. Resulting in the cylinders on one bank in particular being coated in salt residue which hindered cooling causing the overheat condition.

Once we cleared all the salt deposits away and ran it in fresh water the issue ceased to happen.

 

[Big Bubba]

Re: 1995 Evinrude 90hp overheating???

Yeap, I know this problem all to much. Yeap, my dad just bought a 1998 Evinrude, 90 horse outboard that had overheated pretty good and we had to change out the water pump impeller, thermostats, both head gaskets, and the exhaust cover gaskets. Now she runs GREAT!!! without no overheating issues whatsoever.

 

[Big Bubba]

Re: 1995 Evinrude 90hp overheating???

Yes, like Fishfeature, said, clean out all of the salt deposits under the small thin head plates as well as the water jackets inside and under the heads and the thermostat housing and where it installs at into the back of the engine block. We saw alot of white powdery stuff when we were doing the new head gaskets and exhaust cover gaskets and the thermostat housing and where the thermostat installs into the back of the block. Make sure to flush out the water pick up tube once the lower leg unit is off and the thermostats are removed becuase alot of salt sand residue came out when we did this on my dads 90 horse.

 

[renegade15]

Re: 1995 Evinrude 90hp overheating???

Sorry for the delayed response in what I found. It is two-fold really. The powerhead was just rebuilt last november and new t-stats and impeller in march. It is used in exclusively in salt water. Religiously flushed with freshwater.
The first thing I found with these 60-degree looper v-4 motors is that they actually run a tad warmer than ANY of the other motors, sometimes by 15-20 degrees. This was told to me by an old salty omc mechanic and then verified by two other omc shops. He said it is due to the ceramic coating on the block and the compactness in the design to make it lighter and smaller. It never set the alarm off and the heads seemed to be the same temp to the touch. I was also able to touch the head for a few seconds before getting too hot which made the same salty mechanic ask if I knew what the temp actually was, and how I found it. Well knowing that marine gauges are notoriously inaccurate I said "well I am foolishly telling you the 180 temp from the gauge"
This leads me to the 2nd finding...He of course chastised me for believing that, but it was really all I had to go off of when I was on the water and I noticed the higher than normal temp. I got my ir temp gun and took several readings all over the heads with the motor running on the flush ears and with the gauge up about 180. Even in the port for the gauge temp sender I never got a reading above 151 degrees.

So ultimately it has been decided the motor is fine, but I will definitely keep an eye on it!