Force overheating...Help please!!!!

[Noyu]

It's a 89 Force 50hp,I have replaced the impeller and it runs great at low speed but at WOT the motor is really hot and according to the repair manual there is a presure relieve valve but I can't seems to locate it.I have removed the port side exhaust cover can find it!<br /><br />Any info will be very much appreciated!

 

[sony2001]

Re: Force overheating...Help please!!!!

Checkout your thermostat as well.

 

[Noyu]

Re: Force overheating...Help please!!!!

Yes,the thermostate was replaced also and don't know why its overheating!The pee hole at the back of the motor only discharging mist of water and I did even remove the thermostate for a little while at WOT and the motor overheat again in after 5 mins or so.So my guess was there might be something blocking the water passage holes inside the motor.But where should I check for first and how?But before I replace the impeller,the motor was low in compression and I have replaced the headgasket and I am getting about 105 on both cylinder.Will something else went wrong like a crack block or head causing it overheating?<br /><br />Thank you very much in advance!

 

[12Footer]

Re: Force overheating...Help please!!!!

Your compression numbers are low,Noyu. This leads me to suspect the head gasket,or head cover gasket.<br /> This motor does not have a pressure relief valve.<br />It does however, have a wierd shaped intake,as I'm sure you have discovered.<br />These intakes do not provide a good enough seal on the muffs to provide enough water to the impeller. These engines do not have a normal telltale like most outboards. The two exaust ports behind the motor on the leg, emitt both exaust and water. As long as you have a spray or mist, it is isuing just fine.<br />The best way to run this motor out of water, is to submerge the lower unit past the cavititation plate in a large garbage can. I have one set asside for this purpose,and installed a drain at the bottom of the can to drain it (the can,that is).<br /><br />Your compression should be equal on both cylinders, even if they are low. If so, I would suspect a carbon restriction in the exaust ports. Sometimes, a can of decarbon cleaner will restore this lost compression, and greatly improve performance.<br />However, if this carbon has gotten really bad, a teardown is the only way to remove it.<br />Switch to a higher grade of oil also. Wall Mart's "Supertech" TW-C3 oil is cheap and good.

 

[Noyu]

Re: Force overheating...Help please!!!!

Thanks 12Footer for your reply!Yes,I agreed with you on the compression numbers but both cylinder seems the same at 105 and I did replaced the head gasket before I replace the impeller and I think the compression should be between 125 to 150 when new.However since this motor is more than 10 years old I can't really expect a lot!If the motor runs well again I might consider replace the rings after this season.<br /><br />So my primary concern is where should I start to cure the overheating problem?<br /><br />I did check the impeller again and its still in new shape,I did remove the thermostat cover and there is nothing blocking the passage after I remove the thermostat.Should the spring facing out or in when I putting it back?<br /><br />If the impeller is good and thermostat is fuctional,what other possible problems will cause the motor running hot?<br /><br />When I removed the lower unit I think the seal for the shaft at the water pump housing is a little worn,do you think this will cause the motor overheating?<br /><br />I did everything I am capable of and still have no idea why its over heating your input is very much appreciated!

 

[Navigator]

Re: Force overheating...Help please!!!!

Noyu,<br /><br />I had a problem exactly like yours on an old '87 force 85hp I used to have. The engine would run fine at lower RPM, but at WOT it would overheat. I went through the waterpump, thermostat, gaskets...everything you are looking at. My engine also had lower compression similar to yours.<br /><br />What it turned out to be was a scored cylinder wall on one of the cylinders. When you had the head off, did you inspect the cylinders? You may want to spend the 30 minutes and pull the head and check them out.<br />The cylinder walls should be mirror smooth. If they are rough, then this is your problem.<br /><br />It took me almost 3 weeks of tinkering to find this out. I had the head pulled and was going so far as inspecting every inch if the cooling jacket looking for a blockage.<br /><br />Anyways, if it is your cylinder walls, then a rebuild is in order. I honed the cylinder walls on mine, put in larger rings and everything started purring once again. My compression and power returned also.<br /><br />Hope this helps.<br />Nav

<br /><br /><br />------------------<br />Sold the Force and bought my Honda...Oh how I miss those days of Screaming at my Outboard.

 

[sony2001]

Re: Force overheating...Help please!!!!

Noyo your Force should have 150-165 psi. You need a major decarbonization. Check your timing is at 32degrees BTDC. Rumor is 30 is safer and a higher octane may help.

 

[Noyu]

Re: Force overheating...Help please!!!!

Thanks everyone for the reply.Yes Navigator is right,the bootom clinder wall was scored a little bit and when you mean honed the cylinder wall do you hone it yourself or have a machine shop to perform the work?And how much to remove?What size rings should I get after the honing process?Me and my friend are pretty handy and are thinking of doing it ourself do you think is possible?We are think of just remove the piston from the without removing the flywheel do you think is possible?<br /><br />Thanks everyone again!

 

[Navigator]

Re: Force overheating...Help please!!!!

Noyu,<br /><br />I worked in conjunction with my machine shop and bought the new rings first, then honed the cylinder to accomodate them. <br /><br />It's not really hard to do, but you want to have a good technical contact at a local shop that can guide you in the process.<br /><br />If its not badly scored, you may get off easy by lightly honing the inside of the cylinder, and then replacing the rings on the cylinder with new ones of the same size.<br />Once again, its best to have a local expert when it comes to the tolerances. And dont forget, do new rings on both of the cylinders.<br /><br />Nav