78 Johnson 25hp hit limb under water... no shear pin... help!

[jkduab]

Hello all:<br /><br />I have a 78 Johnson 25hp. I was running along at 3/4 throttle when the prop hit a limb under the water. The RPMs went up, but I shut it off quickly and it will start and idle perfectly. I could easily shift into forward and reverse, but no prop movement. I have never hit anything before with this motor and I noticed when I pulled it out of the water, that it doesn't have a shear pin... The prop is splined. Is there a protection mechanism on this type of drive? Out of gear, I can spin the prop with no resistance. I can put it in forward or reverse (motor not running) and I feel some resistance on the prop, but not much and I can spin it either way. Could this be something simple, or am I looking at major gearcase damage? BTW: The prop barely even has a knick on it, so it doesn't appear that I hit it real hard??? Thanks!!!!

 

[Xcusme]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

Well,probably one of two things happened. Either you sheared the prop hub or you stripped the drive shaft/crank junction. The prop has an inner rubber hub that is designed to shear and protect the drivetrain. To test if you have a sheared prop, using a waterproof wax pen , remove prop, at the rear of the prop itself, mark a line across the inner and outer bushing. replace prop and run in gear , on the water. Remove prop and see if the inner hub has moved.If the hub is spun the marks won't line up. Most marine dealers can rehub the prop for a nominal fee.<br /><br />Worse case is that you stripped the driveshaft/crank junction. Easiest way to see this is if you don't have a 'pee stream'. Since the waterpump is driven by the driveshaft when the motor is running. No pee stream could be a stripped crank spline (less likely than the spun prop hub).<br /><br />Report back on what you find.

 

[rickdb1boat]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

I feel some resistance on the prop, but not much and I can spin it either way.

Spun prop.....Take it to a prop shop...

 

[jkduab]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

Thanks for your response... I can tell you that it does have a strong pee stream. I started the motor back up before I pulled the trailer out of the water and it is peeing strong... I did look at the prop shaft and it is turning when I turn the prop and I can feel some resistance when in gear, but nothing like the compression of the motor. The prop slides down on the splines easily. The motor does not jump or make any noise when I put it in gear, but the shifter will easily go into gear???? I've never had lower unit issues at all so this has me confused.<br /><br />Thanks again!

 

[Scaaty]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

New prop.....

 

[jkduab]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

Good morning. I took the prop off last night and I can turn the prop shaft with my hands (either direction) with the motor in gear. This doesn't look good to me. Any more suggestions?<br /><br />Thanks

 

[Xcusme]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

Remove motor cover<br />Shift motor into forward gear<br />Remove prop<br />Hold prop shaft from rotating<br />Can you turn flywheel clockwise without having prop shaft turn? Removing the plugs makes it easier to turn the flywheel... If Yes, then it's time to drop the lower unit and try turning the drive shaft clockwise as above again. Still have no prop shaft rotation? If there's still no prop rotation, it's time to find an OMC manual and open the gearcase. If the prop shaft now turns, the problem is further up the drivetrain.<br /><br />The reason for dropping the lower unit and re-trying to rotate the drive shaft is to confirm either a gearcase problem or a stripped drive shaft/crank shaft junction.

 

[jkduab]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

I'll give it a try. I appreciate your help! I have an OMC manual. I was hoping I would never need it, but oh well! thanks again!

 

[Xcusme]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

Just for grins, please post back with what you find. Your problem and it's solution can help others. Good Luck

 

[jkduab]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

will do... thanks

 

[jkduab]

Re: 78 Johnson 25hp hit limb under water... no shear pin... help!

It was the driveshaft, but I'm back in business. I ended up taking it to a guy that just works on older OMC motors. He was very reasonable. Thanks for the help!