OS XM Over heating

[DeanJohnson]

Hello All,

Last season during a race I barrel rolled my boat and the engine (OS XM air cooled) sucked in water. After this time, the engine would start without a problem, but after roughly 3-4 laps it would build such extreme temperatures that the engine would die. The temps got so hot it would melt the seal of the glow plug and distort the blue color of the cooling head. I took the motor apart and everything looks and feels fine. The bearings are smooth and the rod appears to be in perfect condition.

Any ideas what could have happened to cause this? Any recommendations of what to do to remedy the overheating? I plan on replacing the piston rod and bearings as a precaution, but I’m stumped otherwise.

Thanks for your input.

Dean

 

[Ron B.]

Have you checked to see if the water inlet and outlet are not plugged with something? Make sure you can blow thru the entire water line and rudder pickup to assure there is no blockage.

Sorry I see you said Air cooled...................

 

[Brian Sorgente]

Bearings might be going, sometimes they just plain wear out and suck air even though they feel smooth. Richen it up and if it continues to get worse its probably the bearings. Probably worth checking the piston seal and any other seal/ o-ring in the engine for that matter. Could have picked up some junk on the needle too... Could have a hole in a fuel line or bad seal on a fuel filter...

Hope this helps.

Brian

 

[DeanJohnson]

Hi Brian,

The engine had less than a gallon of fuel through it when it sucked water, but nonetheless, I'm going to replace the bearings. Regarding richening up the needle, for yucks I tried richening it to the point it would barely stay running and the result was still excessive over heating. I ran the needle on a flow meter and the reading is right where I'd like it to be, which should eliminate any possibility of debris clogging the carb or fuel lines.

 

[TimothyJones]

would a bent rod cause the motor to labor and overheat?

Tim

 

[j whiddon]

Make sure your set up didn't change. Check trim and depth. The OS doesn't like a lot of load. It likes to rev.

 

[DeanJohnson]

Set up is fine. The prop has been reduced and pitch taken out. The motor sings, so set up isn't causing the heating issue.

 

[Rene Danner]

Like Brian said bearings, also look at the PTO bearings, leaking air somewhere the way you describe it.

Rene

 

[DeanJohnson]

Hi All,

While disassembling my engine to install new bearings, I noticed there was some slop I wasn't originally aware of between the crankshaft pin and drive shaft hole. The drive shaft hole is 3.68mm and the crankshaft pin is 3.54mm.

Is this too much play and the most likely culprit for the engine over heating? Or, is this variance an acceptable amount?

 

[j whiddon]

Normal.

 

[Eric Canto]

When you flipped the boat, the cold water hitting the very hot piston distorted the shape of the piston. If it still has good compression, you will just need to run it in like a new motor. If you lost compression, it is time for a new piston/sleeve

 

[DeanJohnson]

Thanks Guys,

I'll start with the new bearings and run the boat rich as though I'm breaking in the motor. The motor has great compression and spins perfectly smooth, so I don't believe the piston nor sleeve was distorted. I'm also going to put in a new flex shaft for yucks.

Appreciate your feedback.

 

[Grimracer]

If it did all this after a blow over I would too change the rod.. seems to me we were looking at this last Aug.. no luck yet eh.. rats

Grim

 

[FloridaScaleBoater]

Bent rod or bent crank pin

 

[tom galdys]

It is the rod. When you flipped it was still spinning and the water would not compress. This distorted at least the rod and possibly the piston around the wrist pin cogs.

 

[DeanJohnson]

If it did all this after a blow over I would too change the rod.. seems to me we were looking at this last Aug.. no luck yet eh.. rats

Grim

Yep, same issue. After the Mendota race I pickled the engine and haven't run it since. Trying to get ready for this season and this engine has been a thorn in my side. I'll buy a new rod and replace it with the bearings to see if that works.

 

[SayMikey]

ROD I did it to a picco 45 and it drove me nuts. If you wrote the head clearance down Id bet is different

 

[DeanJohnson]

Hi Mike,

To me that's the most likely culprit, so I bought a rod last week and should have it installed by the end of the week.