Posible to redesign a jetboat into an outboard engine boat?

[Agaponi]

Hi,
I have a Bombardier Sea Doo 15 year 1995, with twin rotax.
I was wondering if its posible to modified the transom, etc... to install an outboard engine. I mean, use my boat first as a plug, then for a quick mold, so i can reenforce some parts more, and build a new hull (maybe more stable for outboard engines), and new transom.
I really like the design of the Sea Doo 15, but im having too much problems with the inboard jet engines.
Please tell me if this is posible (i know its hard), and do i need to modified completly the hull design for this?

Thanks

[sraab928]

I have done this with my Boston Whaler Rage jetboat -

Here is some pics

[Agaponi]

And your impression?
Worst, better or same ride?
Any problems when you take curves?

Seems a pretty good job!

[sraab928]

I love it! The boat runs great. I did have some problems cornering at first but that was due to motor mounting height - once I got that dialed in its been smooth sailing. The boat runs in the mid 40's. I think it should be a faster but I haven't really messed around with props - I just used the one I got when I bought the motor off of ebay.

I built a stringer system to transfer the load to the floor area where the jet intake used to mount up. The Whaler hulls are pretty strong as it is but I wanted to go overkill. There is no flex at all. I used the boat all summer pulling tubes, knee boards etc and examined at end of season and I cannot find any stress cracks or anything. I guess I did ok for a beginner.

[Agaponi]

And did you just add a transom? or modified completly the aft?
Did you use plywood or foam? and how many plywood uses, and how many mat+resin?
Did you put the gas tank more to the bow because of the extra weight of the outboard engine in the aft?

[sraab928]

Pic of transom without jet

Pic of engine area without jet

Intial 3/4 Marine Ply glassed in

Double 3/4 Marin Ply plug glassed in - (resting on ply plug for jet intake)

Final buildup on transom - Three more layers of 3/4 Marine ply - epoxied together and glassed in

Stringers added

Pic looking straight down at what used to be jet intake area

Glassed over and fairing compound added

[Agaponi]

Thanks a lot!
Looks a very good job!
All you use is wood and mat? or even woven roving? coremat?
I want to do the same... but install the engine direct to the boat transom, and not to a metal extension... would i need to get 2 to 2.25inch right?
What about the design of the hull? planning good with outboard engine?
Thanks!

[sraab928]

I used marine plywood - West systems epoxy and fiberglass matt and tape form the local West Marine Store. The boat planes and runs really well - My boat has a 23 gallon in floor fuel tank under the center console. I did add a doelfin to the motor to help with an early porpoising problem.

I don't know how to do it if you want to mount directly to the transom - That to me seems like a much more involved way to go. I think you may take out some strength in the transom by doing so - But I am in no way an expert - just a backyard type of guy.

Good luck

[spjinseattle]

sraab928, it would be awesome to get more information about your outboard repower of your Rage 15. I own one of these boats in Seattle and so far so good, but an outboard repower would be just the ticket if the motor ever goes. Love the size and fun factor of this boat, tows incredibly easy, fits in my garage. But she does pollute a bit as an older 2-stroke and she can be tempormental at times (eg; fuel pump and vapor lock issues recently) = other reasons to repower. Saw your pictures here and read a string on the Continuous Wave board, too. Any additional pictures, advice, steps, parts info. would be super. Also curious how you tow tubes - using the tied-down eyes? Thanks in advance!

[sraab928]

Shoot me a private email and I will send you all the information you need. My email is listed on the Wave under my profile.

As for towing tubes - my boat has regular transom mounted ski tow eyes - one on each side. You can see them in the pictures of the rear of the boat - my Rage project boat also has them so I think they were standard. You then use a ski tow harness that hooks onto them and keeps the ski line away from the motor.

[Agaponi]

how did you calculate the convertion of the jetpower HP to the outboard HP?
i see you first used a 48HP engine, then change to 90hp...
for example, if my boat has (2) 80hp jet engine, what outboard engine HP should i look for?

When u use the 48hp, did you manage to plane the boat?

Thanks

[sraab928]

The 48 never ran - Had carb problems and never saw the water. I had a 70 HP Yamaha that I switched to for trial runs - older motor but ran the boat good. When I was confident in the setup I put the more expensive Merc on the boat.

I used the USCG calculations based on Length, width and weight - At least that was the parameters I remember - I think the boat based on those calculations was good for 115HP outboard. I thought the 90 was about as heavy as I wanted to go.

[Agaponi]

Thanks,
And what was the speed on the 70hp and the 90hp? and before you did this setup (speed with the jet engine)?

[vitomirra]

i just purchased a Rage 1995 and want to convert to outboard can you send me pictures?

Thanks vitomirra@gmail.com

Originally Posted by sraab928

I have done this with my Boston Whaler Rage jetboat -

Here is some pics

[sraab928]

Here is an updated link

http://smg.photobucket.com/albums/v4...%20Conversion/