Over heating when slowing down?

[starsnstripers]

89 5.7 hooked to a OMC stringer. Can cruise along at at any speed and temp stays fine 160* new thermostat. As soon as we slow down the engine goes right up to the red 200+, let cool and do it again. Same thing! Any ideas?

 

[Anchor Management 1]

Re: Over heating when slowing down?

Why did you change the thermostate anyway? Same issue?

 

[starsnstripers]

Re: Over heating when slowing down?

Yes, we thought it was sticking so installed a new one. Update, We noticed the water inlet screen had ben bumped and had some paint on like a 1/8 of it so i'm thinking that the size of that impeller it needs to pump alot of water. Hoping that with the damge/paint closing some of the water inlet may be the culpret. We found a spare OMC trim tab water inlet that the screen was in nice condition and put it on. We'll see on the next run.

 

[Don S]

Re: Over heating when slowing down?

Sounds like it's time for a new impeller. Blades probably won't straighten out on the impeller till they get a lot of rpm built up.

 

[starsnstripers]

Re: Over heating when slowing down?

The inpeller is new Don, we could go along for ever at slow speed and no overheat. Bring up the speed to 3000 rpms and it was ok. as soon as we started to slow down the temp would go up. Strange Symptom!

 

[rthomas]

Re: Over heating when slowing down?

my mc does the same thing and i did the same things as you are, in the end it still does it. ive learned to work with this issue by slowing gradually and if i do need to go to neutral quickly i kick the rpms up to 1200 for a few and then it idles at 150-170. in my case im sure that its heat flash and is commen in a lot of motors, its not harmfull as long as a good cooldown procedure is followed. when i was messing with mine i didnt think that engine water pump was moving water fast enough at low rpm to prevent heat flash, i havnt tried a new wp but i dont see it as a big issue

 

[danond]

Re: Over heating when slowing down?

Overheating is only common in boats with something wrong.

Boat cooling systems are pretty simple. If the impeller is pumping cool water and there are no obstructions in the way of that water eventually reaching the thermostat, the thermostat is opening when the engine gets hot, the circulating pump is circulating, and the warm water is being returned to the lake/river/sea without leaking into something important, your boat will probably cool properly.

If not, start lookin! I found chunks of a thermostat down in the lower hose of my '89 when I got it, partially blocking water flow. Never know what you'll find.

 

[Howard Sterndrive]

Re: Over heating when slowing down?

Grease the swivel bearing in the drive. I suspect you're sucking exhaust gases into the impeller housing there.

unrelated: Can you tell me how did you couple a 1989 engine to a stringer? I have never seen a stringer coupler for a post-'87 crank... did you have one made/modified?

 

[starsnstripers]

Re: Over heating when slowing down?

Howard, There was alot of soot in the housing and even coming out and showing on the outside of the drive cover. What gets greased and how does it prevent the exhaust from getting into the impeller housing? The boat was purchased that way.

 

[Howard Sterndrive]

Re: Over heating when slowing down?

What gets greased and

The swivel bearing - do that free Seloc manual d/l.

how does it prevent the exhaust from getting into the impeller housing?

the grease seals the swivel bushing, so exhaust does not displace cooling water entering the impeller

99% chance it will solve your problem

 

[starsnstripers]

Re: Over heating when slowing down?

Will look into that Howard, thankyou!

 

[starsnstripers]

Re: Over heating when slowing down?

Hey Howard, I did the manual thing. With all the soot around it and on the outside i think your right, BUT. I have a parts drive, and we niticed that the drive were usin does(not) have any grease fittings on the swivel housing. The parts one had two grease fittings on it. Should we swap housings or why wouldn't it have a fitting? it showed it in the manual. It's also a little different shape. Maybe it's the wrong hosing or an aftermarket, I dont know. But we're going to haul it apart again, and see. thanks for that tip.

 

[THE BEEF]

Re: Over heating when slowing down?

Hey Howard, I did the manual thing. With all the soot around it and on the outside i think your right, BUT. I have a parts drive, and we niticed that the drive were usin does(not) have any grease fittings on the swivel housing. The parts one had two grease fittings on it. Should we swap housings or why wouldn't it have a fitting? it showed it in the manual. It's also a little different shape. Maybe it's the wrong hosing or an aftermarket, I dont know. But we're going to haul it apart again, and see. thanks for that tip.

If you look half way down the drive on the backside there is a hole a little bigger
then a nickel.Put your grease coupler in there and see if it locks on a fitting.
Thats the swivel bearing were the seals are.
I had the same problem a couple of years ago,And that fixed it.
The seals are to keep the grease in. When they start wearing out it will suck exhaust gases in ,the grease will seal that area and you should know were the problem is.

Good Luck, BEEF

 

[Howard Sterndrive]

Re: Over heating when slowing down?

"parts drive" makes me wonder if the shimming of the upper gearcase into the exhaust housing was ever done ....
.030" up&down movement max. of the upper inside the exh. hsg. -
procedure is in the Seloc book I believe.

Too much play and the exh. seal will not work and also the upper gearcase can take on water because the o-ring can move up out of the bore at the top.

Too little play and the steering locks.

 

[starsnstripers]

Re: Over heating when slowing down?

We took the swivel housing out tonight. It was bone dry and has no grease fitting or was there ever one there. The parts one had two grease fittings. When we greased them to see where the grease came out it came out in the same spot. we had to remove one fitting and block it off for housing clearance. It also had two extra bolt holes in it. We just installed it and greesed it up and it seems like it will do the trick. The seals are good and the play seems good steering by turning the little gear by finger. The steering was very stiff before. I believs it will run good now. I'm going to check the manual for the different style swivel housing with no fitting. Maybe your suppose to pre grease it opon instalation. weird. the plug and grease hole was there in the housing cover. Aftermarket maybe? No clue yet.

 

[starsnstripers]

Re: Over heating when slowing down?

Let me be clear on this swivel housing situation. The one that came off the drive were using had 8 bolts and no fitting and no seal between the water pocket and exhaust area. The one from the parts drive had two fittings, a seal seperating where the water goes and the grease goes and 10 bolt holes just like the manual except for the extra grease fitting. The 8 bolt no seal no grease fitting one is not in the manual. No wonder the exhaust was heating the water. Strange but hopefully it's fixed for now.

 

[THE BEEF]

Re: Over heating when slowing down?

Let me be clear on this swivel housing situation. The one that came off the drive were using had 8 bolts and no fitting and no seal between the water pocket and exhaust area. The one from the parts drive had two fittings, a seal seperating where the water goes and the grease goes and 10 bolt holes just like the manual except for the extra grease fitting. The 8 bolt no seal no grease fitting one is not in the manual. No wonder the exhaust was heating the water. Strange but hopefully it's fixed for now.

The exhaust is not heating the water. The pump will suck exhaust gases before
it sucks water, path of least resistance. the exhaust gases mix with the cooling water causing overheat problems.