Sheared oil pump drive pin/shaft on 97 Yamaha GP760

[frozenokie]

Just put this new pump in. Now it's not pumping oil due to the above stated. I had no idea either and I now am doing a top end rebuild on it Does anyone know how or why this happens?

According to some of the threads and posts I've seen here, the Yamaha oil pumps are pretty reliable. I'm starting to have my doubts.

 

[frozenokie]

Re: Sheared oil pump drive pin/shaft on 97 Yamaha GP760

I bought another oil pump for a re-run The pump prior to this one had a stiffer shaft tension than this one I wonder if the prior oil pump was faulty afterall????

I checked the function of this new pump by hand turning the pump shaft with my fingers and it did pump oil just fine. So I will try again.

Hope it doesn't screw up this time. I plan on keeping a close eye on it every few minutes until I'm assured I can rely on it.

 

[frozenokie]

Re: Sheared oil pump drive pin/shaft on 97 Yamaha GP760

Thankfully, I put this ski on the trailer when I did... minor abrasion damage on cylinder walls, piston rings not broken or siezed... just a little under-lubed due to that messed up oil pump.

After I get my exhaust joint in on order, I'll have this 760 back together and ready for break-in. All parts cleaned, holes tapped, cylinders honed, new pistons and gaskets. Just anticipating the last part arriving so I can get'er broke-in before cold temps. I'll post a follow-up when accomplished

 

[frozenokie]

Re: Sheared oil pump drive pin/shaft on 97 Yamaha GP760

Got'er ready for the water. Fired her up today just to make sure she would before water bound, but immediately shut it off. Don't want it to run RPM up the 3G's just yet. Want the water to keep it down to the norm. New oil pump is working fine also but will "hawkeye" it anyway throughout the break-in.

Will post another follow-up this weekend afterwards...

 

[frozenokie]

Re: Sheared oil pump drive pin/shaft on 97 Yamaha GP760

Got'er ready for the water. Fired her up today just to make sure she would before water bound, but immediately shut it off. Don't want it to run RPM up the 3G's just yet. Want the water to keep it down to the norm. New oil pump is working fine also but will "hawkeye" it anyway throughout the break-in.

Will post another follow-up this weekend afterwards...

Finally got it in the water Tuesday. Ran like a champ excluding the little "spits" from running double oil

The oil pump worked as it should this time. The previous oil pump must have been defective. So I chalk one up to remember that the oil pump drive shaft (where it joins up with the crankshaft) should turn effortlessly with no resistance at all - like a ball bearing. If the pump feels like a gasket or seal is a little tight on it - then don't use it! That's what the failed pump felt like before it sheared the shaft in half.

I'm happy with it now