Prop Strike With Odd Results

[maj_hazard]

Top of the day all..

After my wife tells me we shouldn't be in "this" channel and just as I respond with "don't be a worry wart" I hit a huge underwater rock with the prop.

1986 Johnson 40HP
Damage is to prop tips and prop is a write off. (bent and gouged) I was running about 2000RPM during the strike.

Funny thing is the engine after the strike ran ok for about 5 minutes then started to behave like it was running out of gas. (Surging) Main tank was low so I changed over to the reserve tank. Engine was hard to start after the change over and once running would not exceed 3000 RPMs. I had the same symptoms earlier in the year which was resolved by cleaning the high speed jets.

I would have assumed if the prop strike had caused internal engine damage that the symptoms would have started right after the strike. I'm hoping that the vibration from the out of balance prop resulted in dirt or something similar being knocked lose and plugging a port or passage some place. The fuel pump/VRO was replaced last year.

Any suggestions as to what I need to check would be appreciated as I'd like to be as prepared as possible when I drive up to the cottage.

BTW you would not believe the glare from my wife after the strike. That gaze is burned into the back of my head as it took over an hour to get back to the cottage at 3000 rpm's.

Thanks and Cheers

Mike

 

[tashasdaddy]

Re: Prop Strike With Odd Results

that is a great motor. less start at the basics. remove the prop, motor off, in neutral, turn the prop shaft and see if bent. next remove spark plugs, and turn flywheel by hand felling for any hard spots. now check spark and compression. post your results here. good luck.

 

[maj_hazard]

Re: Prop Strike With Odd Results

Sorry for the long delay..

The prop shaft did not appear bent but I will be removing it as the seals are shot and I did find water in the lower end after the weekend of hitting that rock.

The engine itself turns over ok when I turn the fly wheel by hand. I removed the plugs and ran a compression test and both cylinders showed about 120PSI.. Nothing seems to be binding or stuck.

I figure something must be bent or damaged in the lower end so I removed it from the unit. Drive shaft appears straight.. I will be tearing the unit down over the next few evenings. One thing that I found was if I placed the lower gear box in forward and turned the drive shaft it took almost a half turn before the prop would begin to move. I was able to move the prop backwards a full half turn. Is this normal ???

One thing I did find was the fuel line from the manifold tree to the electric primer was pinched and may have a small hole. I don't suspect this would have been a player in the 3000 RPM issue but thought I'd throw that out for comment.

The more I think about this (and I had all winter) this is walking and talking like a fuel system issue.. But I want to keep my mind open as I've gone down to many wrong paths in the past becuase I wouldn't open my eyes.

Thanks in advance for your attention and help.

Cheers

Mike