Outboard upgrade plan review

[sPk]

1980 O'Day 25 c/b
Currently has original 1980 Johnson 7.5hp, 2 cycle on original wedge & mount.

I am considering upgrading to a quieter, more efficient 4 cycle with ability to recharge batteries. I've read a bunch of the archives posts but wanted feedback before I make the time & $$ investment.

Here is my current plan:
1. Tohatsu 9.8 20" or 25" shaft w/electric start. Weight is about 90-93 lbs. Which length is recommended?
2. Garelick 71091 4 cycle outboard bracket. 15" travel for motors
(H.P. Rating: Over 7 1/2 to 25 Motor Weight Not to Exceed: 175 lbs. Vertical Travel*: 15 1/2” (39cm) Mtg. Pad: Poly Mounting Board Dimensions W x H x T: 11 1/2” x 10 3/4” x 2” (29 x 27 x 5cm) )
3. Craft or have a plate made to attach to wedge to accomodate wider Garelick bracket.
4. Beef up interior transom with 1/4" marine plywood.

Any comments, suggested options or advice would be appreciated.

 

[HukilauMike]

good plan; you are the only person I can remember who has taken the mount and wedge into consideration when switching from a two to four stroke. For your specific questions:

I think you could get away with a smaller engine if you want to; a four stroke 9.8 is probably more engine than you need. Not too big, just more than you need. However, I am guessing that you are choosing the 9.8 at least partly so you can get the electric start feature. If so, I agree that is a worthwhile tradeoff. I have elec start, and while I love the convenience, my wife views it as a safety necessity.

Shaft length? I would go for the 25". I have a 20" Nissan on my Oday 23, and the prop still cavitate in a seaway, or even when I make a very sharp turn. Deeper is always better, and when there is nothing in the way to restrict how low the prop can be mounted (as on your boat), its an easy decision. If you don't want to or can't spend the $ for the 25", 20" will work, but 25" is better.

For the plate to attach to the wedge, I would try to have that made out of stainless. And I don't think the transom needs to be beefed up; there is a good half inch or more of core in there now. If its in good shape, then I wouldn't bother with the reinforcement.

The four stroke will be much quieter and probably better on gas, but I will say that most people I know (myself included) would rather have a two stroke. Its just easier and cheaper to run and fix. That being said, I know its just not an option to buy a new two stroke anymore. Best of luck, and please post pictures if you can.

 

[emergpa1]

good plan; you are the only person I can remember who has taken the mount and wedge into consideration when switching from a two to four stroke. For your specific questions:

I think you could get away with a smaller engine if you want to; a four stroke 9.8 is probably more engine than you need. Not too big, just more than you need. However, I am guessing that you are choosing the 9.8 at least partly so you can get the electric start feature. If so, I agree that is a worthwhile tradeoff. I have elec start, and while I love the convenience, my wife views it as a safety necessity.

Shaft length? I would go for the 25". I have a 20" Nissan on my Oday 23, and the prop still cavitate in a seaway, or even when I make a very sharp turn. Deeper is always better, and when there is nothing in the way to restrict how low the prop can be mounted (as on your boat), its an easy decision. If you don't want to or can't spend the $ for the 25", 20" will work, but 25" is better.

For the plate to attach to the wedge, I would try to have that made out of stainless. And I don't think the transom needs to be beefed up; there is a good half inch or more of core in there now. If its in good shape, then I wouldn't bother with the reinforcement.

The four stroke will be much quieter and probably better on gas, but I will say that most people I know (myself included) would rather have a two stroke. Its just easier and cheaper to run and fix. That being said, I know its just not an option to buy a new two stroke anymore. Best of luck, and please post pictures if you can.

I have to change engines also as mine is a 15 inch shaft that is not only a reach to operate, but cavities like crazy, even on the lake. I have a Nissan 8 hp. I think I am going to purchase the "sail pro" tohatsu. But only the 6 hp with the 25 inch shaft. Reason? The next size up that offers the 25 shaft weighs 100 lbs. That is too heavy for me to get off and on the boat for trailering. But I am concerned about the power. It does mean that when I get her down to pensicola, fla. I may be underpowered. I will have to pay attention to wind and tide. Does anyone use that engine on their 25 or 26?
I'm thinking about adding the engine below, it should be enough!

 

[sPk]

Regarding the motor size: Our current 7.5hp Johnson 2 cycle has seemed a little under powered when we need to escape a Lake Superior storm with big waves and wind. It has always gotten us to safety but sometimes it is just barely able to keep up. The weight of the 8 hp and 9.8 are the same so it seems like a better idea to go bigger and maximize the power for weight ratio. Also, there isn't a 25" shaft length in the 8hp.

 

[Joe11688]

1980 O'Day 25 c/b
Currently has original 1980 Johnson 7.5hp, 2 cycle on original wedge & mount.

I am considering upgrading to a quieter, more efficient 4 cycle with ability to recharge batteries. I've read a bunch of the archives posts but wanted feedback before I make the time & $$ investment.

Here is my current plan:
1. Tohatsu 9.8 20" or 25" shaft w/electric start. Weight is about 90-93 lbs. Which length is recommended?
2. Garelick 71091 4 cycle outboard bracket. 15" travel for motors
(H.P. Rating: Over 7 1/2 to 25 Motor Weight Not to Exceed: 175 lbs. Vertical Travel*: 15 1/2” (39cm) Mtg. Pad: Poly Mounting Board Dimensions W x H x T: 11 1/2” x 10 3/4” x 2” (29 x 27 x 5cm) )
3. Craft or have a plate made to attach to wedge to accomodate wider Garelick bracket.
4. Beef up interior transom with 1/4" marine plywood.

Any comments, suggested options or advice would be appreciated.

That sounds like a great plan to me. I'd get the Tohatsu 9.8 with the extra long shaft. My friend has that same engine on his Seaward 22 and it pushes that boat right along just beautiful. He has a heavy duty Garelick bracket but it wasn't built for four strokes. He's planning on changing it out to a four stroke bracket.