Raising short shaft transom.

[Frank Acampora]

Here is my Cougar Cub, 10 foot tunnel hull. It was designed for a short shaft engine. I don't have a short shaft in this horsepower and I simply could not get the engine high enough, even though I had already raised the transom about 1 1/2 inches. The previous owner had cracked the transom where it joins the hull and had used some strap iron from the transom running forward--very sloppy and well rusted.

As I said, I reinforced the transom with hard aluminum sheet and raised it about 1 1/2 inches but it was not enough.



SO; With the engine on the boat I raised the transom. Now I need to make a couple of braces for the sides and fill in the transom. more photos to follow when complete.

 

[Frank Acampora]

Re: Raising short shaft transom.



\ Here are a couple of before photos.

 

[Robert D]

Re: Raising short shaft transom.

I raised a transom on a '72 Reinell, to take a 150 hp long shaft outboard. (25") Turned out real well, added knee braces for extra support. Made it a full 2" thick....that thing didn't flex a millimeter when I was done. Not difficult. Plan on making a transom out of 2 pieces of 3/4" plywood laminated together. You'll want to retain your current outer skin, just remove whatever you have on the inside. Position the new, higher transom against the outer skin, clamping it in position. I use epoxy resin, slightly thickened for that. When dry, assemble whatever knee braces you like, and start glassing over them and the inside of the transom. On the outside, grind/sand down the top of the outer skin, so you have a good 2" taper down to where it meets the new transom wood. Then start laying glass to build up thickness. When I got it all sanded and flat, I added a couple more layers of glass to the entire outside, overlapping of course where the extension started. Sanded it all down smooth again. Then paint....or if you didn't use epoxy but regular polyester, you can Gel-coat it.

End result, 2" was way overkill. I had that boat airborne on some big water in the Columbia River Gorge, never flexed at all. Fastest 17' tri-hull in existence I believe! New owner is having a blast with it, says he passes 225 hp bass boats easily I had to sell, to make room for the current project......

 

[redstrat]

Re: Raising short shaft transom.

I agree with Robert D. I think he has a good plan. Frank you're not thinking of putting that 150 on this boat are you? I'm beginning to worry.

 

[Frank Acampora]

Re: Raising short shaft transom.



Well, This was quick and dirty. I want to use the boat this weekend. Sometime in the future if I actually restore the boat I will do a full transom job.

Here is the final product. The two skins are filled with fiberglass and damn! It took a lot. There is about 1/2 gallon of resin in there plus about 1/2 cubic foot of stranded fiberglass mixed into the resin. I used 1/4 28 bolts wherever possible because they are stronger than 1/4 20 and take a higher torque. I would have liked to extend the side plates a little more forward but there was no room to put in another two bolts.

HMMMM! That 150 is still on the stand, waiting. I wonder. Nah-- I was contemplating putting on my 60 with power tilt/trim but even that is too heavy. At rest, the boat sits with the rubrail at or under water.

You can see this boat running before I raised the transom at HTTP://youtu.be/EIhsTDjwIUc

 

[Woodonglass]

Re: Raising short shaft transom.

I'd be real careful and make sure anyone in the boat was secure with their PFD. I'm not confident that the temporary structure is adequate support for the motor

 

[redstrat]

Re: Raising short shaft transom.

I always have been inspired by your "can do, use what you have" philosophy. I couldn't watch the video. Put up a new one when you can. Good luck.

 

[Frank Acampora]

Re: Raising short shaft transom.

Believe it or not, I cant even access this link. However, if you go over to the Chrysler forum and click on Cougar Cub powered with a Chrysler 50, then go down one or two replies and click on the link in cuenta's post, you will see the video.

 

[Frank Acampora]

Re: Raising short shaft transom.



For those Doubting Thomas's who don't think this modification may be strong enough, Here I am bouncing on the anti-ventilation plate with no movement at the transom at all.

 

[redstrat]

Re: Raising short shaft transom.

There you go, showin off again. You didn't steel a road sign to make that modification did you?
P.S. I've never seen anyone drive a boat like that. Please post the video.

 

[Frank Acampora]

Re: Raising short shaft transom.

No, I didn't steal a road sign--I repurposed one that was badly bent during road construction.

A video of this boat running with the raised transom can be seen at you tube: Mini Boat Racer with raised transom. It is a rather long video at 20+ minutes but you can skim through to parts showing the transom at speed--Rock Solid.

Incidentally, raising the engine netted 3 MPH more top speed by GPS--Now at a solid 45 MPH, although it does take longer for the prop to "lock-up" as she breaks over onto plane.

 

[redstrat]

Re: Raising short shaft transom.

Thanks for the update. That boat looks like a lot of fun. It was a bit hard to hear your comments in the video. Sounded like turning was a bit harder with the motor raised. Have you tried more prop yet? The motor sounds great. Let me know if you want a cushion for that seat. I'ld be glad to help out. I've learned a lot from you on the Chrysler/Force threads. Oh yea... just kiddin about the road sign.