Overheating Problem

[Enforcer 24]

I hope someone can help me with this. When I first put my '86 Enforcer in the water off the trailer and start it to let it warm up, it heats up to normal operating temp. and stays there untill I shut it off. When I go to re-start it, say 30 min. later, and start to cruise out of the channel at low speed, the temp gauge rises to hot. If I neutral rev the engine slightly a few times, the temp goes down to normal and will stay there until I shut it off and re-start again. I pulled the T-stat and tried that but still the same results. Water pump I hope, impeller I hope not. Any help would be appreciated. 350 SBC w/ Alpha 1 I/O

[Enforcer 24]

I hope someone can help me with this. When I first put my '86 Enforcer in the water off the trailer and start it to let it warm up, it heats up to normal operating temp. and stays there untill I shut it off. When I go to re-start it, say 30 min. later, and start to cruise out of the channel at low speed, the temp gauge rises to hot. If I neutral rev the engine slightly a few times, the temp goes down to normal and will stay there until I shut it off and re-start again. I pulled the T-stat and tried that but still the same results. Water pump I hope, impeller I hope not. Any help would be appreciated. 350 SBC w/ Alpha 1 I/O

[175checkmate]

Sounds like the impeller is worn. My O/B would do that. Heat up at a slow speed, then cool back down once we where up and running.

[Enforcer 24]

Thanks 175. It could be but then, I think, it would do it all the time though right? It only does it when the engine is already warm and re-started and only heats up once until it is shut off and restarted again. It is fine when I first start it cold off the trailer. The impeller looks like a pain to change but I guess I will have it done by someone. My OMCs impellers were easy, wish Merc. was the same

[Convincor283]

It sounds like a impeller to me, if it was me I would change the impeller and the impeller housing, its really not that bad of a job, and if you do it yourself the cost isnt that bad either.Just buy a book that shows you how,its cheaper then having it done.

[sonoma]

For some reason the impellers in I/O dont seem to last as long as an O/B.
Got that from a marine mechanic I/O impellers should be change eavry year if the boat is used alot .. when you put it back together you should put a bit of white grease inside the housing to help the first start up.......

[FRYED]

You need to replace your impeller. But your engine will heat up when you turn the boat off. The water-cools your boat and when you turn it off the water just sits there and the heat from the engine heats the water. When your boat's running you can touch the exhaust manifolds and they'll be warm. When you turn your boat off the manifolds will turn hot. That's normal even with a new impeller. Once you start the boat and get the water flowing again the engine will cool. You may have some other problems be first change the impeller. Have you ever started your boat up without water hooked up to the lower unit (starting it up on the trailer)? I watch people did this all the time. It takes 3 or 4 seconds to burn up an impeller. It just rubber and the veins will stick to the housing if there's no water going to them. They'll tear right off. Did you see and rubber it the t/stat housing? If so, that's your impeller. And yes, change your impeller every 75 to 100 hours or every spring. It will save you the expense of a motor. Good luck http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

[Enforcer 24]

Thanks Fryed, Sonoma and Convincer. I will do the impeller first and foremost. Never started the motor on trailer w/o water going through the outdrive first. No rubber in housing when took out t-stat. I will give it a shot. Thanks again.

[Chris E]

One other thing on that impeller - even if the blades have a mild shape to them (they don't spring out when the housing is removed) replace it. It runs in an oblong housing which is how it develops it's water pressure. Older alphas use a low volume high pressure impeller, newer ones (gen II) use a high volume low pressure pump. Also. Check the water hose from the drive that's in the transom assy. They get weather checked over time and will leak, giving you a similar overheating problem. Now, if you have to go that far - better have a good look at the bellows in the transom assy. If that hose is rotting, chances are the rest of the rubber back there is rotting. Nothing worse than a sunk boat from a leaking bellows (unless you're the marina fixing it - we looovvvve these jobs). This stuff usually starts to fail at about 10-15 years of age (in my area anyway). different water may act differently.

[vinny p.]

As was said here, the first thing to do is to make sure the impeller is new. If the problem still persists, there are a barage of other things that can cause overheating. Your manifolds or risers can get clogged. Head gaskets. The water pump on the motor, or the thermistat can be bad. Once I was searching for an overheat problem on a 5.7 liter. It ended up being a clog in the hoses that go from the thermistat housing to the risers. There are a couple of check valves and springs in there. They were clogged up with debris. I cleaned it out, stretched the springs out a bit and put it back together. Problem solved..

[Enforcer 24]

THANKS VINNY AND CHRIS. I DO NEED BELLOWS ANYWAY SO I WILL CHECK THE HOSE ALSO. WATER ENTERS WHEN TRIM IS ALL THE WAY UP AND I KNOW IT WILL ONLY GET WORSE. I KNOW HOW MUCH "FUN" BELLOWS ARE. http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/brickwall.gif THE BOAT IS OLDER SO I WILL HAVE TO GO THROUGH IT IN A FEW WEEKS HOPEFULLY. GOT A LOT OF WORK TO DO. THANKS AGAIN. http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

[Chris]

I think the impellers seem to wear on I/O's faster than O/B's because they run so deep in the water. They probably pick up more sand and debris.

[Enforcer 24]

Never thought about that Chris. The lake I run is only 30' deep in the channel and all the "hot spots" are in sandy areas. Never paid much attention to backing the boat up to set the bow anchor and stirring up sand going into the water pick up. No wonder my traps were clogged full when I winterized it. Impeller will be first since a lot of members say they should be replaced every year on I/O's. I have no idea if it was ever changed in the first place. Thanks for your input to jump start my brain for this season!!

[Enforcer 24]

Well guys, after dropping the lower half of my drive to replace the impeller/housing/etc., would you guess that the lower case was FULL of seaweed! They got past the screen in the inlet and blocked water flow to the impeller! Low flow = making steam in engine = overheat. To everyone who helped though, thank you very much. http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif This is a top notch forum. Thanks Chris, great job.