new vibration / delamination?

[Jim Kloss]

Does anyone know if the stringers for mounting an inboard continue forward under the cabin sole? If so, is the sole supposed to be laminated to them? Just noticed a new (?) vibration of the sole near the engine compartment if I put my weight forward, near the head, while running the engine at about 1800 rpm. No noticable vibration if weight is to the rear or off completely. I know I have a bad motor mount on that side.. Any ideas of what's going on and what to do about it?

Jim Kloss
s/v Ambivalence
S2 7.9 #8

[Tom Elsen]

Can someone with an inboard please check for Jim, to see how the stringers are attached / how far forward they run.

Hey Jim
My recollection is that the stringers don't go any farther forward than the bulkhead, and that the stringers are attached to the sole via some fiberglass mat (running in an "L" from the sole up onto the stringer).

If the stringers are rotted, they'll need to be replaced. A bad mount on one side could cause the prop shaft coming out of alignment, and to vibrate. It could also cause the prop to impact the hull.

If you need some on-site advice, see if you can find the guy who repaired the big cat over at Green Cay last year. He rebuilt a lot of the forward window jambs. Did nice fiberglass work and knew what he was talking about. Good luck.

[Dave Eserkaln]

That is correct, the engine mounts are just blocks of cedar and plywood laminated to the floor of the engine compartment with some heavy glass. They do not extend outside of the engine compartment.

I took my engine out last winter and found that the wood inside the mounts was totally saturated with water. They aren't very well sealed and the cedar just sucks it up like a sponge. Mine weren't rotted yet, but I'm sure they would have eventually.

Dave Eserkaln

Jaya #123

Thanks Dave. TE

[Jim Kloss]

OK, I guess that's good news. Any idea of what might be transfering the vibration?

Jim Kloss
s/v Ambivalence
S2 7.9 #8

[Tom Elsen]

Hey Jim
Check the whole length of the prop shaft, from the connection point, through the stuffing box, through the mounting strut, to the prop itself. Check for any wiggle / wobble / looseness. If I had to guess (which is exactly what I'm doing) I'd bet it's in there somewhere. And make certain that there's plenty of clearance between the prop and the hull.

Do you have a folding prop? I forgot. Those can play hell with the bearing surfaces in the strut.

[Jim Kloss]

Engine was in neutral, so the vibration couldn't have been caused by shaft, cutlass bearing or prop. The engine was running as smoothly (?) as usual; it was placing my weight forward that seemed to cause/ exacerbate vibration of the cabin floor aft.

Jim Kloss
s/v Ambivalence
S2 7.9 #8

HHHHmmmmmmmm? Let me think about that one.

[Tom Elsen]

If the motor was in neutral, then the only thing I can imagine is that there are both solid and soft portions of the mount, and this causes the motor to vibrate unevenly. It's got firm support at certain points, little at others. Maybe when you shift your weight either (a) the engine shifts just enough to make contact with something or (b) it shifts just enough to exacerbate the unevenness.

[Jim Kloss]

Tom, I think the only feasible next step is for you to come sailing the next time you visit St. Croix!

Jim Kloss
s/v Ambivalence
S2 7.9 #8