I/O to Outboard Conversion

[Javajim]

I have a 1971 Glassply with a Merc165 6 cyl. stern drive and am considering removing it and replacing it with an Outboard on an Armstrong Bracket, what HP outboard should I use to get equivalent performance? My understanding is that the place where the HP is calculated is different between an I/O versus an Outboard.

I am looking at the right balance between performance and fuel efficiency.

Thanks in advance.

 

[QC]

Re: I/O to Outboard Conversion

Lots to consider on this but the first is probably balance. Even with a lighter OB, this repower is often a failure. The I/O has lot's of weight lower and farther forward . . .

That 165 made around 140 hp at the propshaft, a 115 OB would probably yield similar results and a 150 would be waaay fun if your transom plan can handle it. Do some searching here though, my understanding is that most are unhappy after a job like this.

BTW, welcome aboard!!

 

[Javajim]

Re: I/O to Outboard Conversion

Lots to consider on this but the first is probably balance. Even with a lighter OB, this repower is often a failure. The I/O has lot's of weight lower and farther forward . . .

That 165 made around 140 hp at the propshaft, a 115 OB would probably yield similar results and a 150 would be waaay fun if your transom plan can handle it. Do some searching here though, my understanding is that most are unhappy after a job like this.

BTW, welcome aboard!!

How do these become a failure? Is the boat unbalanced or does the transom fail?

 

[tashasdaddy]

Re: I/O to Outboard Conversion

most who do this, are not happy. the boat is designed with the center of gravity for the type drive system. you are adding a bracket, and moving the motor back. thus changing the design of the boat. you will also have to beef up the transom, as the stringers support the I/O, not the transom.

 

[ondarvr]

Re: I/O to Outboard Conversion

The old Glasplys use the same hull design for the OB and IO, just a different transom, this was the norm for boats of that era. Use a flotation bracket and you shouldn't have any problems.

The big problem is cost, a bracket can run a couple thousand $$ and the OB may cost that, or more, now figure in the controls, steering, glass work, etc and you have a big project.

I had a 19' Glasply that I was going to do the same thing with, the problem was when I added everything up it was going to cost me around $6,000 to $7,000 to do it. I could buy a Glasply for the same or less money that was completed, plus it would come with a new trailer, electronics, downriggers and other goodies.

Old Glasplys sell for much more than other brands around here, even the very old ones.

 

[Javajim]

Re: I/O to Outboard Conversion

My situation is that I already have a 115 Yamaha 4-stroke on a 16 foot Livingston. I am thinking that its too much motor for the boat. I just spent the best part of the last 3 weeks wiring it up and will be taking it out next weekend. If it is too much motor then I will probably be looking for something smaller (Honda 90?) and will need a home for the 115.

The motor on the glassply still works, its just that its over 35 years old and I would have a hard time taking it out very far, with the bracket and and outboard, i can breathe new life into the glasply, just need a new teleflex cable. Plus it would open up the whole aft end of the boat and make a great fishing platform.

If there are any CG issues, I could open up the deck and put some ballast, a fix box and/or another gas tank in it and give it longer legs. The hull is in GREAT shape, and I like how far forward the cockpit is, giving a huge space for the aft deck.

What is the market for a Merc165 and the outdrive? Can I get much for them?

Also, how would I be able to approximate the top end and cruising speed with the 115?

Thanks for your help.