1987 Starcraft Islander Rebuild w/ 3.0 L Mercruiser

[Watermann]

Yeah that is a bit of rivet overkill for that transom plate :lol:

I agree, wood is not the best choice for knee braces, a double set like my V5 has should be able to take up the stress. I would be careful about trailering that much motor hanging there and use a transom saver at all times.

Another thing to think about on OB boats is how the splashwell adds to the structure of the stern. It ties in the sides of the hull with the transom. The SW in my V5 also is tied into the knee braces.

 

[JDH-GL]

Yeah that is a bit of rivet overkill for that transom plate :lol:

I agree, wood is not the best choice for knee braces, a double set like my V5 has should be able to take up the stress. I would be careful about trailering that much motor hanging there and use a transom saver at all times.

Another thing to think about on OB boats is how the splashwell adds to the structure of the stern. It ties in the sides of the hull with the transom. The SW in my V5 also is tied into the knee braces.

That's good advice! I'm thinking structurally, the splash well would sort of tie the sides of the hull to the transom as you stated - which is essentially how the knee braces would tie in the transom to the bottom/stringers.

 

[Woodonglass]

I'd use aluminum angle and attach them to the stringers and transom at a 45 degree angle.

 

[JDH-GL]

I'm going to try an build a splashwell at the same time as I brace up the transom. I've attached a drawing showing the general plan that I've come up with.

The idea is to use plywood and aluminum angle to create the bracing below the "splashwell". I checked the strength of the 1/4x20 bolts I'm using and with 8 additional ones (4 per motor mount) this should provide more than enough support. I also plan on using several stainless screws to stiffen up the aluminum angle to the plywood.

My main question now is if I should is a back plate underneath the motor mounts and bolt the angle through, or if I could just set an array of pop rivets? These connections would be in shear instead of tensions like the bolts going through the transom.

I'm going to set them with a few pop rivets for now, but I'll leave it ready to switch to bolts if necessary. It's just going to be a pain to use bolts as there isn't much access to the inside of the motor mount.

 

[JDH-GL]

Well I put something temporary together. Gives me time to figure out exactly how I want to build the splash well. It actually really stiffened the transom up. Wasn't any real noticeable flex anymore.

 

[Watermann]

Post a pic that shows the entire area, perspective over all.

 

[JDH-GL]

This is the best I have at the moment:

 

[Watermann]

Oh yeah a knee brace attached on each motor mount, that should be a solid set up. The braces do look to be a bit high to me as they should be lower than the top motor mount bolts for the SW angle..

You can see my V5 SW and the location of the top bolts and drains.

 

[JDH-GL]

Thanks for the picture! The supports are temporary for now, until I can get stuff cut and drilled to the shape I want for the splashwell. I'm planning on creating a bench seat across the back too.

I'm off to warmer climates for a few weeks, but will keep working on it once I'm back.