Replacing front motor mount citation 195 merc 3.0

[bryceheinz]

Just picked up a boat that has a broken motor mount. When engine torques the port side of the mount lifts off the hull. Its tied into the rear stringer which is not rotted. I was wondering if the motor mount is Glued to the hull and then glassed over of if its just glassed? It seems that whatever held it to the bottom of the hull has failed over time. Any ideas on repair?

 

[jigngrub]

The MM and stringer are supposed to be bonded to the hull with adhesive AND glassed into the hull. Someone has done a really crap job for that mount to break loose.

I suggest removing and replacing both MM's and probably that port side stringer too. It doesn't matter if it's rotten or not, if it isn't bonded to the hull properly it is of little use.

 

[Rickmerrill]

For this one it would really help to have some pictures of the mount and stringer and where it is separating. Some are glued and some aren't.

 

[bryceheinz]

No Title

Its lifting off the bottom of the hull. Are the engine mounts glued with an air gap between them to the hull like stringers are? I don/t really feel any rotted wood underneath it. Could I extend the mount to the side there and glass it all in instead of completely removing it? I am going to replace the floor over winter and just want to finish off the season with this one.

 

[Rickmerrill]

For engine mounts and stringers the recommendation is to fill the gap with PB or, less popular, PL premium glue to prevent hard spots on the hull. If you could grind back the whole area, clean it and get some biaxial on it you might get a few weeks use out of it. I am not recommending this that's just how I'd approach it if I was forced to. I doubt you could lift that side of the engine enough to do any prep work under the mount. You're not doing your drivetrain any favors running it with the engine moving around. Assuming that is the port side are we looking at the bulkhead forward of the engine in the upper part of the picture? If the mount is lifting what don't I see a crack where the top of the mount is tabbed to the bulkhead?

 

[jigngrub]

For engine mounts and stringers the recommendation is to fill the gap with PB or, less popular, PL premium glue to prevent hard spots on the hull. If you could grind back the whole area, clean it and get some biaxial on it you might get a few weeks use out of it. I am not recommending this that's just how I'd approach it if I was forced to. I doubt you could lift that side of the engine enough to do any prep work under the mount. You're not doing your drivetrain any favors running it with the engine moving around. Assuming that is the port side are we looking at the bulkhead forward of the engine in the upper part of the picture? If the mount is lifting what don't I see a crack where the top of the mount is tabbed to the bulkhead?

I agree.

Even if you can jack/lift the motor enough to get an adhesive under the MM it probably won't hold with the crap/crud/corruption under there.
Tabbing the MM to the hull is the only temporary fix you have, and it may or may not last.

Your boat is already broken, do you really want to run the risk of tearing something else up?

Consider ending the season early and start working on your boat now while the weather is nice.

 

[bryceheinz]

I am going to cut it out and replace it. I cut a hole in it and found mush for wood underneath. Looks like 3/4 plywood and some glass work and Ill be good. What kind of gap do I need between the mount and the bottom of the hull? I will use PB instead of PL adhesive. Is 3/4 thick enough to support the engine?

 

[Fastatv]

I am going to cut it out and replace it. I cut a hole in it and found mush for wood underneath. Looks like 3/4 plywood and some glass work and Ill be good. What kind of gap do I need between the mount and the bottom of the hull? I will use PB instead of PL adhesive. Is 3/4 thick enough to support the engine?

You may have some plywood rotted or missing as I have never seen a motor mount with a single piece of 3/4 plywood. I would think three to four 3/4" pieces minimum, laminated together, and no air gap between mount and hull, however, there are more experienced persons here that will will jump in and provide you the correct direction, and materials required to obtain the best end result. Woodnglass, Jigngrub, and several others.

 

[Rickmerrill]

From that pic it looks like you have a substantial motor mount I'd put it back as close to original as possible.

 

[jigngrub]

I am going to cut it out and replace it. I cut a hole in it and found mush for wood underneath. Looks like 3/4 plywood and some glass work and Ill be good. What kind of gap do I need between the mount and the bottom of the hull? I will use PB instead of PL adhesive. Is 3/4 thick enough to support the engine?

That isn't the only mush/rot you have in that area, if you'll look around I'm sure you'll find more... there always is.

 

[bryceheinz]

No Title

Stringer, mount and part of the floor. the old mount wasn't ever glued down. Just glassed over. Should I cut it to follow contour of hull and then glue it to hull as well as glass it?

 

[jigngrub]

the old mount wasn't ever glued down. Just glassed over.

Doesn't that make you wonder what else is screwed up in the boat and not put together right?

 

[Rickmerrill]

Now I get it. Are you sure the bulkhead is good? Looks like it has a dark area to me but things are a little out of focus. Was the mount a solid block or just a shell made of 3/4" ply? Those look like lag screws and it's hard to believe they are held in with one layer of 3/4" ply.

 

[bryceheinz]

3 layers 3/4 ply glued together. That's why I was wondering if I should cut it at an angle.

 

[fishrdan]

How ever this is repaired, be sure to align the engine after the repair is finished. If the engine isn't aligned after the repair, you could wear out the engine coupler, and then be in for a much bigger repair.

Engine alignment tools can be bought on Ebay for $50.

 

[Rickmerrill]

The more contact area with the hull the better. So that thing was just bridging over the center of the hull? I'd waterproof any bare wood you're not glassing over. Coat with resin with hardener on the slow side, when it tacks up add a layer of CSM over it. Same coating before you lay the 1708. Between mount and hull about 1/4" gap fill with PB filler. May be easier to lay the PB on the hull thick then squeeze it down. Use some wood sticks as stops, pull them out then squeeze down just a little more. PB fillets on all inside corners. Nice wide tab onto hull for strength say 6", 8", 10". Woodonglass recommends 4 layers of 1708 for engine mounts.

 

[bryceheinz]

So i know i said I would use pb but pl sounds so much easier. Will it work?

 

[Rickmerrill]

Not sure strength wise but it will take at least 72 hours to dry, lay it on thick, even longer. It tends to off-gas and have bubbles so not good for making fillets. If you put PB or glass over it the off gassing will create bubbles in them too. You can put PB in a freezer bag, cut the corner off and squeeze it out like decorating a cake. Ready to continue in an hour.

 

[bryceheinz]

Ok I watched enough videos. I feel comfortable making the peanut butter. As far as the gap goes between the mount and hull, do I want to leave whatever I use as spacers in there or no? Also where do I get cabosil? Napa?

 

[bryceheinz]

What about this stuff to attach MM to hull http://www.westsystem.com/ss/six10-introduction/