Drive Train Confusion

[ataylor233]

Hello all, i have a 1993 carver 350 aft cabin the previous owner somehow bent the shaft it also had a little damage to the prop. This winter i removed the shaft and props and had them all refinished (New Shaft) .... reinstalled everything dropped the boat in the water .. and again anything over 1200 rpm it wobbles again... a bit frustrating as you can imagine... Any idea what could be causing this ? could it be the struts holding the shaft? if so where can i get some of those ... Thanks in advance...

[bud37]

QR_BBPOST could it be the struts holding the shaft?

The simple answer is yes it is possible, but first, how was the fit between the new shaft and the engine/trans/coupling ?? Even a few thousands more than spec can cause issues as far as I know. Perhaps the engine mounting could be adjusted to correct, hopefully.

Did you check the alignment of the strut or install a new bearing before fitting the new shaft ?

[ataylor233]

QR_BBPOST could it be the struts holding the shaft?

The simple answer is yes it is possible, but first, how was the fit between the new shaft and the engine/trans/coupling ?? Even a few thousands more than spec can cause issues as far as I know. Perhaps the engine mounting could be adjusted to correct, hopefully.

Did you check the alignment of the strut or install a new bearing before fitting the new shaft ?

no i didn't i assumed everything was straight since the shaft went right in i have to admit i did have to lift up a little bit to connect the coupler to the engine... the engine has never been moved.... do you think i can lower the engine mount to fix this issue or should i pull the shaft and check the struts

[Viper]

When out of the water, first thing is to check your strut bearing/s. Then when you insert the new shaft through the strut/s, check to see if the shaft is centered when going through the hull. If it's not close to center, the strut is either bent or needs to be aligned. When all that is okay, insert the shaft through the shaft log and install the coupler on the shaft. Mate the coupler to the tranny flange (do not bolt yet), and using a feeler gauge, check the gaps at 12, 3, 6, and 9 o'clock. Any clearance more than .003" requires the engine to be aligned by moving it up, or down, or side to side depending on the clearances found between the flange and coupler. If you only have one strut on each side, you might need to support/center the shaft and log assembly when mating to the flange as the weight of the shaft could force it down which will throw off the alignment process. You should not have to lift up past the center of the tube, if you have to, the engine is out of alignment.

Not clear if you redid shafts and props on both sides. If not, the other side should be checked also so that you know it doesn't contribute to a vibration as well. Did you take your coupler/s to the machine shop and get them refaced and fitted to the new shaft/s?

[bud37]

One thing to add to that excellent explanation....if you do find the strut damaged , be sure to check the mounting area for cracks etc due to impact or soft strut mounting strata.

[ataylor233]

QR_BBPOST When out of the water, first thing is to check your strut bearing/s. Then when you insert the new shaft through the strut/s, check to see if the shaft is centered when going through the hull. If it's not close to center, the strut is either bent or needs to be aligned. When all that is okay, insert the shaft through the shaft log and install the coupler on the shaft. Mate the coupler to the tranny flange (do not bolt yet), and using a feeler gauge, check the gaps at 12, 3, 6, and 9 o'clock. Any clearance more than .003" requires the engine to be aligned by moving it up, or down, or side to side depending on the clearances found between the flange and coupler. If you only have one strut on each side, you might need to support/center the shaft and log assembly when mating to the flange as the weight of the shaft could force it down which will throw off the alignment process. You should not have to lift up past the center of the tube, if you have to, the engine is out of alignment.

Not clear if you redid shafts and props on both sides. If not, the other side should be checked also so that you know it doesn't contribute to a vibration as well. Did you take your coupler/s to the machine shop and get them refaced and fitted to the new shaft/s?

Yes both side props have been redone the other side is pretty smooth... My main question is I had to lift up on the shaft to get the coupler to mate with the trans. Now even though the engine has never moved would it be wise to lower the back of the engine and align it with the shaft. Or should I wait until I'm out of the water... Because now I kinda understand where the wobble is and I think it's because I lifted the shaft to fit.???

[Viper]

An impact changes things, even if there isn't an impact but are just replacing the shaft you need to check alignment. If you lifted the shaft up past the center point of the tube to meet the engine, then you've lifted it too high and must lower the engine to accommodate. The process should have started before you were launched though, strut alignment should have been confirmed first. I should also mention that once you confirm the position of the external gear, you need to let the vessel rest in the water for a minimum of 24 hours before you check and adjust the engine alignment.