1985 Evenrude 90 hp overheated

[bigheaded5]

I took my motor for its 2nd run and it worked very well. I let my daughter drive back and she did 6 mph for about a mile and the high temp alarm sounded for the first time all day. The tell tail was streaming, so Im not sure where to look for the problem.

I read a previous thread about DEFLECTORS being faulty....are deflectors the HOSES that bring the water to the heads? Could it be that simple? $2.99 ? Generally when guessing or troubleshooting in life, I like to start simple and cheap and work my way up unless its obvious.

 

[Bob_VT]

Re: 1985 Evenrude 90 hp overheated

The deflectors help route the water by blocking passages to insure proper flo direction. Yes they are cheap to replace but nothing comes w/o a price. You need to remove the heads to get to them. Normally I replace the head gaskets and I also clean out the outer water jacket and replace those gaskets too.

I normally do the deflectors, gaskets and thermostats all at the same time.

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

Im wondering if the style of driving could have been the problem? I was at 3/4 throttle for about 30 min, then my daughter took over and went from 30 mph to 6 for about a mile...... Wasn't until 15 min after going 6 mph that the alarm sounded. Could the slow RPM of the motor but being under a load cause the engine to heat up?

 

[boobie]

Re: 1985 Evenrude 90 hp overheated

On a mtr that age, good chance the deflectors are bad. But don't forget about the thermostats.

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

well, we TRIED to sneak out just into the channel today to fish without setting off the HIGH TEMP alarm but it caught me. We got 10 min into the trip, didnt even reach the channel and the alarm started screaming. Turned around obviously and headed home with my tail between my legs.

Did a little trouble shooting, and found that.... the starboard thermostat was stuck OPEN and the port was stuck CLOSED. I thought this suspicious so I took them both inside to prove it. Boiled them in a pot with NO CHANGE! Have an appointment tomorrow at 9am with the local parts store for new therms and gaskets. $50 fix. who said B.O.A.T stands for Break Out Another Thousand lol

 

[emdsapmgr]

Re: 1985 Evenrude 90 hp overheated

Once the boat is at planing speed, the pressure relief valves in the thermostat housing open-flooding the powerhead with extra cooling water. (regardless of what the thermostats are doing.) Once you drop back down to displacement speeds, these valves close and the engine is dependent upon the thermostats only for cooling. Probably why it overheated when your daughter started driving (so slowly.)

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

Once the boat is at planing speed, the pressure relief valves in the thermostat housing open-flooding the powerhead with extra cooling water. (regardless of what the thermostats are doing.) Once you drop back down to displacement speeds, these valves close and the engine is dependent upon the thermostats only for cooling. Probably why it overheated when your daughter started driving (so slowly.)

No kidding? Im at a loss.... what is a PRESSURE RELIEF VALVE and where is it located? Today I idled out of the marina and into the 5 mph line (1/4 mile) and the High Temp alarm went off...... your saying if i was on plane, the engine would have cooled fine?

 

[Tim Frank]

Re: 1985 Evenrude 90 hp overheated

When did you last change the impeller?

 

[AEROCOOK]

Re: 1985 Evenrude 90 hp overheated

The pressure relief valves are in the thermostat block / housing. If you are buying a thermostat kit it should come with new springs and seals for the pressure relief valves, gaskets, and of course the stats. The Sierra kit I bought for my 110 Johnson came with all these parts, not sure about the contents of other brand kits.

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

I know....that's on the list. This is the first season I owned the motor and if I wasnt on vacation with my kids this week, I would lay it up and change it today. I know, I know....it should be changed NOW but I just want to get on the water with my kids till Sunday THEN the new impeller is going in. The water is flowing...The tel take is strong but i took off the hoses and the water flow is GREAT.

 

[BonairII]

Re: 1985 Evenrude 90 hp overheated

I would check compression .

The fact that it overheated and you limped it back to the dock....it may have caused some damage(hopefully not).

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

STOP lol no damage the second the temp alarm went on, I did a 180.... dont scare me! lol

 

[emdsapmgr]

Re: 1985 Evenrude 90 hp overheated

It is very possible that if you were on plane when leaving the marina, that the engine may not have overheated.

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

can you explain WHY? I assume the white star shaped parts over the springs are the PRESSURE RELEASE valves.... how do they allow water to pass when on plane vs at low speed?

 

[Tim Frank]

Re: 1985 Evenrude 90 hp overheated

The design/shape of the impeller and the water flow characteristics often make a failing impeller show up at low RPMs....temp alarm going off after a short run at low rpm..
BIL had those symptoms, bought a new impeller, but put off installing it for "just one more run."
The shop installed the new impeller for him at no charge ... .... when they rebuilt his power-head. :facepalm:

Your call....

 

[Tim Frank]

Re: 1985 Evenrude 90 hp overheated

STOP lol no damage the second the temp alarm went on, I did a 180.... dont scare me! lol

Lots to be scared of....
"The second the alarm went on", the motor should have went off....that tone is not meant as a suggestion just to turn around and motor back the way you came. :facepalm:

 

[BonairII]

Re: 1985 Evenrude 90 hp overheated

that tone is not meant as a suggestion just to turn around and motor back the way you came. :facepalm:

That's exactly what I was alluding to.

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

Thank you again for all your help. I changed the stats...gaskets and grommets. Easy enough fix but DAMN Evenrude, can you make the 3 bolts less accessible? lol Glad I had a beer close by while making the 1/16th turns with the box wrench. The swivel socket wouldn't fit....

 

[bigheaded5]

Re: 1985 Evenrude 90 hp overheated

oh..... I never did a compression check when i first got the motor, so doing one now wouldn't tell me much about before and after the overheating.... but the motor ran like a champ yesterday.... LOW and HIGH speed...idled smooth and went through the power range fine.

 

[emdsapmgr]

Re: 1985 Evenrude 90 hp overheated

After removing and re-installing the thermostat cover, welcome to the "skinned knuckle" club. It's even worse on the bubble back models...