CMB 45 HR lost low end power

[BobGutsell]

Hey Guys

At the second to last event I went to, the last couple of heats the engine was going lean and stalled when launching.

Thought nothing of it, so turned up to race this weekends after having cleaned out the needle and fuel filter prior.

Same thing, if I launch the boat and get it on pipe when luanched it will run the whole heat. If it falls off pipe then it loads up stutters as if it's gone lean then stalls.

Get it back on the bench and restarted, same thing get on pipe at launch, good run. not qyite on pipe stutter and stalls.

I'm running the same pipe length and prop I always run but now am losing the low end. Have tried backing low end needle right out but no change.

Can I have some ideas for things to check, or what might be happening?

Cheers

Bob

 

[carlnoki]

possibly time for new bearings.

same thing happened to one of my 21 valvolas.

changed the bearings and right as rain again.

 

[BobGutsell]

THanks I'm thinking the same thing. Did you notice the ones you took out were notceably rough? The ones in my engine don't feel too bad, although it is full of after run oil.

 

[carlnoki]

they felt ok, but the new ones felt ALOT better.

 

[Duck899]

Bearings....

 

[Don Ferrette]

THanks I'm thinking the same thing. Did you notice the ones you took out were notceably rough? The ones in my engine don't feel too bad, although it is full of after run oil.

By the time a bearing feels "noticeably rough" it's already past the point of replacing, I change bearings at the end of each season in most motors (after about 15 heats on VAC91's, they're tough on bearings). Look at it this way it's cheap insurance vs. a $500 (or more) motor.

 

[tnrcboatracer]

THe bearings keep the crank centerd in the case bore which helps maintain the oil film seal between the two bearings. If the bearings get bad enough to allow the crank to rub the case, the seal will be gone for good, and the motor will suck air through the front end making it impossible to find a needle.