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Early Crusader 454Velvet Drive question

S

sbright

New member
"Need some help. Thought this

"Need some help. Thought this might be the best place to pose the question. I had a vibration.. took props off the boat (had to loosen the flanges on tranny and shaft to get the prop puller to fit)and noticed that one prop was hitting the strut. It actually machined itself down some against the strut. Taper on shafts and props seems right, old props did this last season as well, btw problem seemed to go away with new props. Putting the props back on, the keyway ends inside the strut. Also, inside the boat, the keyway coming out of the flange on the other side looks to be about an inch further out than the rubbing side. So here's the question, has anybody heard of a Velvet Drive tranny having 1/2 an inch worth of travel to it? Boat runs fine otherwise. I think I'll end up putting longer shafts on it, but thought somebody might be able to shed some light on my problem. I saw drive savers on the net but thats around $500...for a pair."
 
"Stanley:

Velvet drives sho

"Stanley:

Velvet drives shouldn't have that any fore-aft 'play'. Check your motor mounts to be sure they are sound and secure.

The shafts should be 'whole' coming out (going aft) of the shafts before the taper starts. Your MFG should be the best source for how much (ask for total length, too). From memory, mine are at least an inch. two reasons - ensure proper load on cutlass and, as you've found out, prop puller clearance.

I could see a few different scenarios for how this has occurred. If the engines have been out/swapped, they may not have located them properly for the shafts - engine box/deck clearance? Check the motor mounts' location on the stringers. The stringers should have 'pad areas' for the mounts. They could have also been that way for a while...you never know.

The shafts could have been changed (installed too short) or made too short (cut off old coupler). Separate the couplers and make sure the shaft is inserted into the couplers, all the way to the shoulder at the flange end. I've seen the keyways cut longer than necessary, so wouldn't be too concerned about that. I would expect both shafts to be machined similarly.

I think you'll find the drive savers are more economical than new shafts. Finally, once you get the shafts corrected, make sure the alignment is correct and you shouldn't have any problems for a while."
 
"Mark:

Thanks for the insig

"Mark:

Thanks for the insight. Are you saying that when the keyway is cut into the shaft it is in the taper portion only? and not into the straight part of the shaft? I agree with your thought about an older coupler being cut off (and thereby ending up with a shorter shaft). I didn't have it spread far enough (or knew to look at the time) to see the nut of the shaft inside the coupler. The couplers that are on it now are pinned AND keyed. There's a 3/8 inch rod that pins the shafts to the couplers. The mechanic couldnt get the pin out last year, it finally sheared all the way and I was able to get it out about a month ago, put a new one in. Do you know if they make 5inch dia extenders? Can you think of any reason I couldnt get by with a pair machined out of aluminum? There is a 5 inch rod available on ebay for cheap. At $500 for the drive savers I think I might be looking for a used lathe.."
 
"Stanley:

Actually, I'm

"Stanley:

Actually, I'm not sure about the keyway at the prop end. I was referring to the coupler end where i've seen them just right to up to an inch longer than necessary. After re-reading your post, I did some www searching and found one recommendation - look here:
http://www.unitedpropeller.ca/propinstall.htm
They also address some of other Q's you had.

I know of no 'shaft stretchers'. The drive savers are certainly a concept to build from. Make sure you get an appropriate grade of aluminum, one with enough shear strength if you pursue this.

All the couplers I had apart have NO nut on the forward end. The solid ones are machined very tight and are held on by set screws. The split version has clamping bolts as well as the set screw.

I've never seen any that were pinned; all had keyways. search the www for prop shaft coupler and you can find several pictures of what they look like. If your pin is where the set screw is, i'd say somebody had a bad day and did a hack job putting back together. You may want to check with a prop/shaft shop to get their opinion(s).

Also, I reread what i wrote about the coupler to shaft connection and it may not have been real clear. The bore in the coupler is all the way thru. The forward end of the shaft's coupler has a pilot that mates in a recess on the gear's coupler. The shaft should extend all the way forward into the coupler. The shaft's face should be close to but not extend beyond the pilot. this is a press fit joint, no nut on this end (fwd) of the shaft."
 
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