Honda BF8 Slipping at high rpm's

[paxnobis]

Can't figure this one out! Low RPM's are fine but as soon as I increase RPM the engine spins but there's no corresponding increase in prop RPM. Dismantled lower end and checked shaft ( the square lower shaft slips into the top shaft housing very tightly....and gears at clutch end seem fine....nothing seems wrong. Any thoughts would be appreciated. The engine is for the dinghy on our sailboat now in Trinidad and we are stateside with a return planned for December. If we need parts we need to buy and ship ASAP. Thanks

 

[Flakeys]

Re: Honda BF8 Slipping at high rpm's

Take a look at your prop and make sure the splines or bushing or what ever you have are not stripped or the bushing spun.

 

[paxnobis]

Re: Honda BF8 Slipping at high rpm's

HI,

Thanks,

The prop is protected by a shear pin through the prop and shaft. It was intact. Hmm.... I'll try to find a picture of the prop online to see if there might be a chance that the hub/prop might spin even if the shear pin is still there.....??

 

[gss036]

Re: Honda BF8 Slipping at high rpm's

It sound like the gear inside the lower end are chewed up, but you had it apart and it looks ok. Is the drive shaft to the gear case good? If it is protected by a shear pin, then I don't think you will have a rubber hub in the prop. Also, remove the prop and look at it. Nothing beats a hands on visual inspection.
Is the prop metal or plastic comp? How much flex is there in the prop? Is the prop cavitating?

 

[paxnobis]

Re: Honda BF8 Slipping at high rpm's

Thanks for the thoughts

The engine is 2000 miles away but I think I looked at all the gears quite carefully as well as the downshaft square socket and spline end. I even used a thinner shim on the clutch to make sure the gears were really engaged.

Did not look carefully at the prop except to note that the notches for the shear pin were not worn away......

Could it be that the outer part of the prop would spin on the hub that accepts the shear pin? I don't have any pictures to reference so I can't tell you if there's a rubber sleeve between the hub and the prop.

 

[jimdd810]

Re: Honda BF8 Slipping at high rpm's

You do have a rubber hub in that prop. If it is spun it will cause that problem take it to a prop shop and have them check it. If you have a spare prop try it and see what happens. The shear pin is not a shear pin it is a drive pin. Hub could still be spun.