Stern Drive Prop Question

Hi All,

After researching, testing, and asking questions, I think I have finally narrowed my problem down to the prop, so here I am .

I have a 1988 Wellcraft 190 Open Bow Classic
(dreaded) 3.7L 165
Alpha One Gen 1

Last year I was pulling up to a sandbar and *barely* nudged the top of a log with the outdrive in gear (at idle). Skeg bent worse than it already was, but other than that everything appeared fine. Ever since, I've had a vibration or wobble or shake (call it anything you like) in the steering wheel. When at idle (in Forward or Reverse) it is more pronounced in the wheel, but not visible in the outdrive. The opposite is true on plane. Less noticeable in the wheel, and you can visibilly see the outdrive shaking right to left (horizontally).

It only occurs IN the water, and IN gear. On the muffs, I could balance a wine glass on top of the outdrive with it in gear. I have checked the following: U-Joints, Skeg, Prop Shaft, Alignment, Steering Pin, Steering Cable and Gimble Ring (Vertical and Horizontal Pins).

I had the 21" Alum. Prop rebuilt that was on the boat at the time, but now I am starting to second guess his work, as I have tested everything else I can think of. I know he reworked the fins, but (especially being that it is a flo-torque II hub) I wonder if it needed to be re-hubbed.

So I have two questions..

#1 - Has anyone ever heard of a prop causing this kind of "Shake" in the outdrive on plane?

#2 - A friend has a known good 18" Pitch Prop. The questionable existing is a 21". Will it be ok to test it with my friends?

Re: Stern Drive Prop Question

If the prop isn't machined perfectly, it will create a shimmy at higher r's. It sounds like a slightly bent prop shaft could be a possibility also if you haven't checked that.

Use your buddy's prop to check it against yours, just watch the r's because it will want to rev higher at lower speeds.

Re: Stern Drive Prop Question

Check for a worn gimbal ring. If there's any slop between the gimbal ring and upper gimbal pin it'll do exactly what you're describing. Perfectly smooth on muffs, but sideloads in the water will drive it back and forth because of the sloppy fit. Very common problem on older outdrives.

Have someone hold the steering wheel, then grab the end of the outdrive and try to move it back and forth. If there's more than an inch or so of movement at the most you need to find out where the slop is.

Re: Stern Drive Prop Question

Turns out the Prop was indeed the culprit. Put a friend's on today and it was like a new boat. I had no idea it could cause that much of a vibration but still appear to be fine. I think I'll be calling the shop that refurbished it for me .

Thanks again for the help!