Poor water circulation in Yamaha 4.3

[Miss Behavin]

I have a '92 Chaparral Cuddy with a Yamaha 4.3L<br />V-6. Since first starting the engine after the storage season, the engine has overheated. The first thing I did was replace the seawater impeller, which appeared to have some damage. Still, the engine overheated and some of the water hoses from the thermostat housing were still cool. Thinking the thermostat must be bad, I replaced that also. Still, the engine overheats. I am considering removing the risers to check for clogging or malfunction. Also, there are no apparent leaks from the engine water pump, but I am wondering if, since the boat runs usually in salt water, there might be some clogging inside the water pump. I would appreciate any advice if anyone has seen similar problems and might know of possible remedies.

 

[DJ]

Re: Poor water circulation in Yamaha 4.3

Miss B,<br /><br />I ASSUME this is a raw water cooled engine/drive. If so, concentrate on the mainfolds and risers. If the water cannot flow through, you'll overheat.<br /><br />The Yama drive is a very nice one.

 

[Miss Behavin]

Re: Poor water circulation in Yamaha 4.3

Thanks for you answer, I wonder, can risers and manifolds be removed and cleaned and/or repaired?

 

[Boatist]

Re: Poor water circulation in Yamaha 4.3

I agree with DJOHNS19 I would pull risers and look for blockage between output of manifold and riser. I do not know if boat stays in water or you trailer it but here is a couple of ideas.<br />With motor running and warmed up check temp of both exhaust manifolds If it right they should be warm but not very hot and both should be about same temp. When they first start to stop up usually engine will cool down at low RPMS and get hot at high RPMS.<br />If it is on the trailer put your ear muff on and turn water on but not so hard that you force water thru system. Start motor and see how much water comes out of prop. It should be a good steady heavy flow. Should be cool until thermostate opens but then just warm. Another thing you can do is take is take off hose that runs from motor to exhaust manifold hook it to a hose and run over side and start engine. Engine will cool down quick if manifold is pulgged. You should probably pulg input to manifold. You can not run it too long this way as have no cooling to exhaust manifold. You can do this on water also. If you warm it up first be careful as water is hot. The hose should put out a steady stream of water all the time hot or cold. This is also a good way to check how much water your water pump in outdrive is pumping.<br />If you run in salt water life of manifold is 4 to 6 years if you flush every time. When manifold starts to go bad rust and scale very offten plug up water output of manifold. You can clean it out and it might be ok for a while but be aware the next thing that happeneds is start to leak water back into exhaust and rusts exhaust valves or worse yet run water into cylinder and fills it up then when you try to start it on compression stroke engine freezes up an you bend the rod for that clyinder since you can not compress water. If you think it is close to that to be safe pull the plugs and turn it over a couple of times and watch for water out of spark plug holes before you put plugs back in and try and start it. Sorry to be so long. Good luck and let us know what you find.

 

[Boatist]

Re: Poor water circulation in Yamaha 4.3

One more thing to check is engine water pump. Make sure belt is tight and pump is turning. This pump circulates water in engine and when thermostat opens pumps hot water out of engine.

 

[Miss Behavin]

Re: Poor water circulation in Yamaha 4.3

Just to let you know. So far I have replaced, thermostat, cleaned risers, new impeller, it is still over heating!!! Doesn't seem like the sea water pump is pumping the water into the engine.

 

[Boatist]

Re: Poor water circulation in Yamaha 4.3

Pull the hose coming from the outdrive to the engine. Put you ear muff on or make sure it is in water. Start engine and you will know if it is pumping water.