Keith,
Sean McGuckin replaced the damper plate on his M35B, without taking the engine out of the boat. He did a great writeup on the project, including pictures. It was in the Nov 2006 issue of Mainsheet, on the Tech Notes CD, and also on this website. I'm not sure if the bell housing on the M25 and M35 are the same, but at a minimum you should read the article. Hope this helps.

Keith:

I had to remove the tranny on our boat to do a damper plate job as Tom mentioned. I suspect replacing the tranny is even simpler since the damper plate stays on the engine and you won't need to do that step. I attached a picture of the bell housing and you can see it has lots of holes to accomodate different transmission types...my Hurth had 4 bolts holding it on. Some of the holes are also for alignment pins.

Unless something is very different on the M25 from the M35 you do not have to remove the bell housing to remove the tranny. The tranny bolts to that housing. In fact since I believe the aft engine mounts are connected to that housing you really don't want to mess with that unless absolutely necessary.

I had to do much of the job on my belly and leverage was a challenge, but being patient and looking closely before you apply a wrench makes all the difference. I also needed to slide the shaft aft about 5 inches to allow room to slide the transmission out of the damper plate coupling (spline).
Happy to help if have any other questions.
Good Luck!
Sean

P.S. Take some movie clips and we'll post the job on the new website!

The older M25s are different than the M35s. The transmission bolts through the bell housing. The bell housing has to come off the engine. I'm surprised you've found a new HBW50, they've been superceded by the ZF6M that's one inch longer, same as the ZF10M (HBW100) that are on the M35Bs.

I'm probably going to be replacing mine next winter and will be needing to shift my engine forward, since it seems to set farther aft on my 1991 C34 than what I've observed on hulls from the late eighties.

Craig is correct, your the transmission is unfortunatly bolted on from inside the bell housing with no access to the hadware without removal on the M25 and 25XP.
This is problematic as the rear engine mounts are located on the bell housing. This will necessitate supporting the engine with blocks under the sump to support the engine with the bell housing removed.

A word of caution, as Craig indicated the bell housing has both bolts and guide pins holding it it place there are a couple sneaky bolts, most are have the heads on the aft side but there is at least one near the starter as I remember that has a nut and bolt and one on the oposite side of the engine that is just a bolt with the head on the forward side of the flange. If these are not removed, it will make you wonder why the housing is not coming off. The guide pins can also be a problem if they are rusty and they will not easily slide off of the bell housing. Be careful prying the bell houlsing off as it is cast and can be cracked if pryed on to hard.

This Job can be done in situ, but short of the forward mounts, the wire harness and engine controls, you may after its all said and done wished you had pulled the engine as a package. Even just lifting it and moving it forward onto some blocks makes the task easier than wrestling with it in place with limited access to the hardware. Lifting it and moving it forward can be done by using a four by four across the companionway with a chain hoist or block and tackle.

The engine mounts fought me, as the lock hardware was quite corroded, this necessitated replacement of my rear mounts. You should realign the engine after this work is complete or if you are feeling lucky, unbolt the mount base from the mount logs and leave the adjustment untouched and hope it is still close enough after bolting eveything back in place. Do check it with a feeler gauge before bolting the coupling together.

No doubt the task will broaden your vacabulary, let us know if you learn any completely new words or terms.

Keith, I posted a picture of the bell housing and components on the image's section. I do not know if it will be of any help to you.

Steve

Keith:

I went and checked the M25 parts manual and sure enough my post may have been misleading...the M-25 mounts are indeed inside the bell housing (seems a strange design to this mechanical engineer -- I prefer fastners on vibrating components to be exposed so the torques can be checked).

I've attached the picture that shows the bolts go inside out (see #10).

Sorry for any confusion my earlier post with the M35 may have caused.

Sean
Mahalo Lou
C36 #1748
Mystic, CT