Synthetic motor oil instead of gear oil

[nammer]

curious if any of u guys have or recommend against using synthetic motor oil instead of gear oil for the jet pump?

i ask because instead of leaving a bottle of gear oil open for years, i can just use a tiny bit from my oil changes

 

[racerxxx]

Do you put 75w90 in your car? Stick with the correct weight. Royal Purple, Mobil 1, etc all make GL5 Synthetic. I know guys hate the smell, I actually like the smell of gear lube.

 

[LouDoo]

If you change the pump oil once a year and you have three ski's a bottle should only last about 2 years, stick with GL5 75w90, I use Mobil 1 and it only costs about $10.00 a quart.

Lou

 

[SabrToothSqrl]

Gear lube turns me on... takes me back to the days of my Wrangler on 35s and diff fluid changes yearly...

 

[68ragtop]

Do you put 75w90 in your car? Stick with the correct weight. Royal Purple, Mobil 1, etc all make GL5 Synthetic. I know guys hate the smell, I actually like the smell of gear lube.

There you go! you could start your own line of shop air fresheners!

 

[Dr Honda]

motor oil doesn't have the ability to protect the roller bearings, and it doesn't contain anything for high-pressure lubrication. So... it's a bad idea.

If you don't' like leaving it open... give it away. The shelf life of oil is VERY long. As long as it's capped... it shouldn't be a problem.

 

[nammer]

thanks everybody, I'll go with the gear oil for sure!

 

[Strizzo]

it would seem that you wouldn't need the heavy duty oil to keep the roller bearings happy, since they're not exposed to a ton of force (fairly balanced prop, no reciprocating mass like a crankshaft), but keep in mind that all of the load from the impeller forcing water through the jet pump nozzle is taken up by the thrust bearing, which likely means a lot of shearing on the lubricant (shearing is the actual crushing of the oil molecules, which breaks them down and reduces the lubricating effect of the oil). you could possibly pick up .5 or 1mph on a race ski with the lighter oil, but you could have to rebuild jet pumps as often as every race weekend. definitely not a rec ski setup.


fwiw, nascar teams have been using teflon coatings in their axles for years, and for the longest time they saw little to no advantage from it. until, one time someone forgot to fill the axle with gear oil before qualifying, and they picked up a couple of mph. it was then that they realized that the major source of friction in the axle was the lubricant flinging around inside, and the teflon coating would allow them to use much lighter oil. now i think they use 0w motor oil in their diffs.

 

[Robj]

I would just use the correct synthetic gear oil.

But on another note, my Volvo Penta SP outdrive uses straight 30W motor oil. Kinda wierd to be putting motor oil into a gearbox but that is what is uses, and these outdrives are more less bullet proof.

 

[Strizzo]

its not unheard of, honda recommends 10w-30 in their manual transmissions, or did in the 90's and early 00's

 

[nammer]

thanks strizzo, pretty interesting info

 

[Brucetafer]

I would just use the correct synthetic gear oil.

But on another note, my Volvo Penta SP outdrive uses straight 30W motor oil. Kinda wierd to be putting motor oil into a gearbox but that is what is uses, and these outdrives are more less bullet proof.

yep my 275A VP outdrive is the same, but I was told by a 40 year veteran mechanic of VP that gear oil is MUCH better in that application... but i didnt notice a difference in the wear from my annual teardown... well see....

 

[Robj]

yep my 275A VP outdrive is the same, but I was told by a 40 year veteran mechanic of VP that gear oil is MUCH better in that application... but i didnt notice a difference in the wear from my annual teardown... well see....

I have heard otherwise, in colder water the gear oil gets too thick and does not circulate properly through the drive causing oil starvation and failure. I just use the 30w and haven't had any problems.

 

[nammer]

good thing i'm in FL