[jerryyow]

I got a beeep beep ....warning on the alarme at over 4000rpm's and traced down the problem to the oil pump gear. My oil pump gear that drives the oil pump shaft appears to be made of plastic and has sheared off most of its threads inside the shaft housing. I vacumed all of the shavings, and the pump works at low engine RPM's.
How much of a job is it it to replace this gear in the engine block, and what is the downside of removong the pump shaft and just running motor on 50/1 premix??
Engine has about 300 hrs of runtime and warm compression is 115psi on 5 cylinders, and 85psi on the #6 bottom cylinder.
Any ideas as to why this gear failed??
Is this a common problem??

[gss036]

Lots of posts on the subject. Major engine tear down required to replace the gear. Mercury makes a kit/plug to replace the gear so you can run pre-mix. That by far is the cheapest fix. There is also a kit for an electric oil pump, but again cost big bucks.
Do a search and sit down w/a big cup of coffee and enjoy the reading.

[grootski]

This is a common problem because the gears are plastic. Basically designed to fail. By the time you get the beep the engine is damaged. You now have low compression in one cylinder which would indicate scouring due to lack of oil. Pull the cylinder head and check it out. Do not run the engine with a damaged gear. Mixing is a little inconvenient but it is the only sure way to know an engine is getting oil. The cost of repair far exceeds the hassle of mixing. After the engine is repaired, remove the gear on the pump and reinstall it. Hope this helps.

[CharlieB]

This is a very common problem on motors that are run at higher RPM.

Most ALL the hot rodded motors leave the gear out and strictly run pre-mix.

Replacing the crank gear requires splitting the cases, so you can understand this is not an easy fix.

That sixth cyl is hurt, enough so that you really are only running on 5, and should be repaired before Spring.

You have my vote for leaving out the crank gear, oil pump shaft, and oil warning module, get Religious about mixing your fuel.

[jerryyow]

Thank you for the feedback, ran the boat again with 50/1 mix in tank, removed the pump shaft, and left the pump on the engine.to plug the hole.
Also dissconnected the switchbox to oil/temp module connection wire to stop the beep beep warning from the oil warning. Installed a waterpressure gage to monitor waterpump pressure to powerhead.
Operating RPM (5800rpm) and idel performance seemed normal and hopefully there was no major engine damage to the engine as compression came up on the weak #6 cylinder to 100#s after running the boat for a hour on the lake.
Thanks again

Jerry