volvo penta 280 to Cobra SX transom conversion

[_vn_]

i just scored an VP 5.7GL engine with VP sx cobra outdrive for very good price, trying to figure out what is involved in the project
my boat is Bbayliner Capri cuddy, not completely sure about year, hull number says its 1982 and title says 1987 ... go figure, i gave up looking here is ID which looks like 1982 third quarter BLBA54CJ1182-3
currently i got volvo penta 280 outdrive with aq175 engine in it. i realize that hole in transom needs to be smaller vor cobra and after some searching here i see that entire transom wall needs replacing. frankly i can't picture how this can happen without gutting out most of my boat which i am not looking forward to. Engine is under the hatch which is smaller width than beam. i am not near my boat at this moment, its 350 miles away, but i've got some pictures and from what i can recall that stringers go all the way to transom so taking the hatch opening width and stringers in the way i can't really picture how can i put in entire transom back in there (taking it out i guess is easier since it doesn't need to come out in 1 piece ). the closest that i found is this picture of transom reinforcement

here are some of pictures of the boat that i actually have


does my transom wood go all the width of beam or is it only the reinforced in the center where outdrive is? or is it both ?
does anyone have similar boat or worked on one like it?

thanks for help!

 

[4Winns2]

Re: volvo penta 280 to Cobra SX transom conversion

I can't speak to your Volvo Penta to Cobra conversion. On my 4 Winns the transom is two sheets of half inch going the length of the beam. There is one more sheet of half inch that just circles the key hole.

You'll hear here it a lot on the forum, if your transom has rot then the likelihood that your stringers and deck have rot is high. I'm having to pull my deck (which is rotted anyways) and cut stringers to tear out and rebuild my transom. I would safely say you'll have to do the same. In any event, I wouldn't go to all the trouble of replacing your transom without checking your stringers once you get the deck out. Just my 2 cents and you'll hear more expertise on this as people respond.

 

[_vn_]

Re: volvo penta 280 to Cobra SX transom conversion

i was just putting on smart tabs and didn't seem to have dark shavings when drilled holes but even if transom is OK how would I make a hole smaller without taking it all out?

 

[4Winns2]

Re: volvo penta 280 to Cobra SX transom conversion

I assume you're referring to the keyhole. If there isn't a conversion kit available, and I doubt there is then what I've read here is you need to class over the inner transom and the outer layer and re-cut a keyhole to fit the Cobra.

 

[GWPSR]

Re: volvo penta 280 to Cobra SX transom conversion

There are several threads here of people doing OMC-to-Merc conversions, and Penta-to-Merc would be similar.

Check this one as an example: http://forums.iboats.com/boat-resto...9-glastron-ssv-177-omc-mercruiser-475895.html

Essentially, you replace the transom without a keyhole, also building up the hull in the old keyhole (feathered back on both sides so that it becomes one new skin), then figure out the geometry for a Merc transom shield and gimbal housing so that the alignment of the driveline is in spec. Most likely will involve new motor mounts as well.

I think Oops did a conversion in his thread as well. That one is a must-read for all members, just because.

 

[_vn_]

Re: volvo penta 280 to Cobra SX transom conversion

the more i read about it more i am thinking about donor hull or adapter plate for 700-800$
i will have a better look at my boat this weekend and make some test drills to see what condition my stringers are as well as transom
also will figure out how to put transom ply back in - that will be tetris puzzle
anyone has dealt with adapter plate and how is it affects geometrical position of outdrive ? this is what it looks like i guess

 

[_vn_]

Re: volvo penta 280 to Cobra SX transom conversion

spoke with local boatsmith about this, he suggested aluminum 1/4 inch plate inside and outside, seal, cut hole and be done. claims he has done it before and it works just fine. any thoughts? how hard is it to get hole properly cut? what are the tools needed? thanks !