93 Mariah engine mount

[Mariah212]

Hey guys, I need some advice on what wood to make this engine mount box out of...Before anyone ask, the main stringer and the transom are fine as well as the other side engine mount...I was thinking of stacking 3/4" marine plywood together here and then glassing over? thank you..

 

[MikeSchinlaub]

Measure to the bottom side of the glass at the top first, to make sure stacks of 3/4 will work out, preferably with a layer of csm between each. Otherwise, yes it would be fine. Don't forget to set it in resin putty too.

 

[Scott Danforth]

that stringer looks suspect. do a test drill about 2" up from the hull bottom into that stringer and look for moisture/rot

 

[alldodge]

.Before anyone ask, the main stringer and the transom are fine

 

[Mariah212]

that stringer looks suspect. do a test drill about 2" up from the hull bottom into that stringer and look for moisture/rot

Appreciate it...I did...It's not perfect, but it's gonna have to work..It's not soft or anything.. You know my last boat was a Sea Doo that didn't have any wood in it and I got this thing and really didn't want a boat with any wood in it for this reason...

 

[Mariah212]

I got a better look at it after a few mentioned the stringer...Apparently, that rotted part isn't the actual string, but a board on the inside.. I don't really understand how this thing is made...I took a little cut of the floor out to see what is behind it and it looks like two untreated boards or something.. Shouldn't the stringer just be right there??

 

[MikeSchinlaub]

Looks like stringer to me. Not being a smartass here, but what do you think a stringer is?

It's usually one or two sheets of ply laminated together, then attached to the hull with thickened resin underneath and glass wrapped around and to the hull. Sometimes they are like a hollow glass panel epoxied to the hull, where the epoxy breaks and causes stress cracks all over the bottom (lookin at you Supra).

What I see here is rotting stringer wood which has delaminated from the glass.

 

[Scott Danforth]

I see lots of hours of labor

 

[Mariah212]

Looks like stringer to me. Not being a smartass here, but what do you think a stringer is?

It's usually one or two sheets of ply laminated together, then attached to the hull with thickened resin underneath and glass wrapped around and to the hull. Sometimes they are like a hollow glass panel epoxied to the hull, where the epoxy breaks and causes stress cracks all over the bottom (lookin at you Supra).

What I see here is rotting stringer wood which has delaminated from the glass.

I'm not taking it that way in the least..I'm asking questions.. If you look at the pic and if you look near the edge of the blanket that board just stops at that bulkhead next to gas tank...I imagine those boards on the backside are the stringers? I have a rotozip and I'll cut some the floor out and get a better look...Appreciate your tips..

 

[alldodge]

Your looking at a full gut in the engine room, most likely the whole boat

 

[Scott Danforth]

The rest of us have been there, usually about 15-20 years ago with a boat from the early 90s

Mike does this for a living

Most of us just dable

 

[Mariah212]

Thanks...This all started as a 383 project with aluminum heads and then went sideways when I removed the engine and didn't like the way the bolts came out and one wasn't all the way down...I'm not doing a whole floor deal and all that...This will be my last boat with wood or just my last boat...It's just total BS.. You find rot and then it's like pulling a thread on a sweater...It's a 93 from a high quality manufacture and it still just rots away.. I appreciate all your guys help!

 

[Scott Danforth]

Boats are designed to last 15-20 years . Yours is 33

Aluminum heads need a heat exchanger

Your boat is not structurally sound.

 

[MikeSchinlaub]

The extra board could just be a spacer or a means of connecting all of the ply layers vertically. I wouldn't worry much about it.

I agree that this really needs a full tear down and rebuild. If it's too much work for you, which would be perfectly understandable because it's a LOT, don't waste your time and money with the engine.

Don't let Scott over sell me, I do it for a living but I'm mostly dumb labor. He has actual smarts.

 

[Mariah212]

I get it. I'm gonna come up with something repair wise, but it will probably not be perfect..I can't just throw 11k away and I'm not gutting the thing..
The 383 thing is obviously on hold...On the aluminum heads....Just conversation here...I think a lot of guys are running aluminum heads on BBC etc. in fresh water with a magnesium anode that screws into the head..

 

[MikeSchinlaub]

You CAN just replace the motor mounts and ignore the rest. We do a lot of stuff like that, not many people have infinite money to dump into an occasional weekend toy.

You could still get a lot of use out of it. Just keep in mind the structure is weakened, so don't push it hard. No towing or wakeboard ing or any of that watersportsy stuff. It's not worth risking cracking the back and sinking with the family on board.

 

[Mariah212]

I'm not gonna ignore it, but I'm gonna come up with something more reasonable than ripping the entire boat apart when the current rot area is 12-16 inches.. I can come up with something...

This isn't a slight to any of you fellas in the least as this forum has some dudes that know about hulls...Back in like 2012 I had a Sea Doo boat that came apart at the lifting strake.. It was pretty bad...A lot of the dudes on here were trying to tell me to remove the cap etc... All this crazy BS.. I ended up cutting a pumpkin hole in the upper deck, doing a backside repair, taught my self to spray gelcote and the boat is still running fine...Sold to a guy in SC last year...

I appreciate all your guys input for sure.. I take your input, Youtube, common sense and I try to come up with a reasonable solution....Thank you......I don't tow anything other than a dog to shore to play on the beach...

 

[MikeSchinlaub]

Cut out the bad portion of stringer, cut a really shallow angle into the remaining, bed the new section in with thickened resin, 2 layers of csm and one of biaxial roving 12 inches on each side and a minimum of 6 inches down the hull. Then scuff the mount side and add in the motor mounts. Smooth it out a bit with a grinder, brush gel, and done.

 

[Mariah212]

Thanks...I have to get into a little more....The outer board you see is toast..I'm gonna cut that out...The two sheets behind it seem to have separated? They are not rotten..When boards delaminate can you not dump some epoxy between them and the clamp? Trying to learn here Sir.

 

[Scott Danforth]

There is no good repair that isn't a correct repair.

Do some test drills of the stringers and transom