SD-50 whinnying noise

[pondering65]

Looking for technical thoughts and input on a dilemma. Yanmar saildrive SD-50 seems to be whinnying at a higher than normal pitch. Just completed a cone lapping work order and stern oil change due to slipping and dockside testing was fine. Left dock and completed a 90nm run and it performed great, thrust was good, shifting good, all fine, did not appear to overheat or anything. So anybody out there know of a reason for increased whine noise from a cone lapping work-order or where and how I should troubleshoot this.

[B73C]

I too have just done this same procedure so am interested in what you find. I also have just had a successful dock test.

I've heard that if the four nuts that draw the studs for the pinion shaft back into the saildrive are either not fully engaged (or are misaligned or loose) it can be the cause of excessive gear noises.

[Jim Cate]

Whinnying noise?? Maybe too many HORSEpower!

Jim

[pondering65]

B73C - you are exactly on target. That is what I found. Those 4 nuts backed off due to engine vibration during the 90nm run. Tighten and added extra torque with some blue thread locker and all quite since...

[tkeithlu]

Oh, Jim....

[KylesSailing]

Hello, Thanks for your post. I have the same problem with a whining noise after SD50 cone relapping and fitting upgrade kit. B73C's solution didn't appear in my thread - is it the nuts connecting the SD50 to the engine that needed retightened?

[tkeithlu]

Whinning from gears comes from two sources that I know of. One is lack of oil, which doesn't sound like your problem, and imperfect alignment, which does. Each gear tooth is cut to roll against another, with teeth being a different shape depending on the number of teeth in the gear. If that alignment gets off a bit, it whines. You can hear the same no-quite-fitting whine in reverse gear on your car, since cutting a gear to fit in both directions is apparently a problem.

So, the retorque your bolts advice is right on.

[KylesSailing]

Thank you. That was exactly the problem; I retightened the nuts between the saildrive and the engine and all quiet. I did tighten them before I started the engine so assume once the engine ran, the gears meshed and the nuts became slack.

[LittleWing77]

Originally Posted by KylesSailing

Thank you. That was exactly the problem; I retightened the nuts between the saildrive and the engine and all quiet. I did tighten them before I started the engine so assume once the engine ran, the gears meshed and the nuts became slack.

Apparently those bolts and their torques are one of the most neglected/underestimated elements re: maintenance. You perhaps don't have the Service Manual (?), but I know that for another brand of sterndrive I was learning on recently, the Manual does instruct a retorque after the first hour of motoring after reassembly.

It also recommends annual maintenance + retorquing for those bolts. Wonder what the Owner's Manual says. (*For anyone who many not know - and sorry for stating the obvious for those who do know - but Owner's Manuals and Service Manuals are expressly different; Service Manuals are MUCH more detailed!)

Happy boating this season, Kyle!
LittleWing77