59 Glasspar Seafair sedan possible transom rebuild?

[ianmoore]

Hello everyone,


I inherited a very old and broken 59 Seafair sedan in the classic way that many of us do, through the promise of a working boat that was far from.

After having it for about 6 months, and realizing that it was in bad shape, I decided to rebuild it. Having zero experience with anything boat or vehicle body related, it was a long, strange trip. I ended up grinding it to the hull, rebuilding the stringers, floors, and transom, and doing a relatively solid rebuild of the boat. I made a ton of mistakes, but the boat has held up well, and I have enjoyed it tremendously with family and friends here on the Puget Sound for the last 6 years.

I put a 1988 Mercury 115 on it, and so far the transom has held up admirably. I have meticulously kept the motor up, but it is finicky, and I've decided it's time to repower with someone a little more reliable and environmentally friendly.

As I'm looking at new motors, I'm noticing that most of them are much heavier than the Merc. If I were to go with a 115 4 stroke, they seem to sit around 50-75Lbs heavier. I was already a little concerned about the transom and it's ability to handle the Merc, so I am looking into possibly rebuilding the transom to accommodate a bigger motor. My initial rebuild was 2 sheets of 3/4" marine ply glued together and then glassed pretty thoroughly.. I don't remember exactly how I did transom, but was methodical, went slowly, and ended up with what looked like good solid glasswork. I was a little concerned about the 1 1/2" transom, but it held up to the 115 was no stress cracks or anything.

As I'm considering this project and gathering some research for possibly diving in, I wanted to hear any thoughts on different routes people have taken..Coosa vs Marine.. Thickness vs engine size.. Any additional structures tying transom to body(outside of glass). Please share any thoughts you have!

Thanks
Ian

 

[briangcc]

I'd double check that weight difference. When I went from 2 stroke to 4 stroke it was about 200lbs difference. That's a full grown adult sitting on the transom....enough to sink the boat further into the water about 1-2".

That extra depth may be the difference between whether you can run a 4 stroke or not.

 

[ianmoore]

I'd double check that weight difference. When I went from 2 stroke to 4 stroke it was about 200lbs difference. That's a full grown adult sitting on the transom....enough to sink the boat further into the water about 1-2".

That extra depth may be the difference between whether you can run a 4 stroke or not.

Definitely looking into that. The Merc TOP 155 is 295lbs. The 4 strokes I'm looking at are 350-375LBS.
I'm Considering this as I look into different transom materials as well

 

[matt167]

The question isn't if the transom can hold the weight.. If it was properly rebuilt, it can... The real question is, does the boat have enough buoyancy to hold the extra weight.. Glaspar never gave a max weight, or a max hp in 1959 for the Sefair sdn. Likely because the boat could use all the hp that was available at the time and still need some..

I think a 90hp Suzuki is where you want to be. If you go to 115hp, you can do it at 400 lbs. They happen to be the lightest motors in their class, pretty much all the way across.. It would be 343lbs for a 90hp which is only 28 lbs heavier.. It will run like an old 100hp.

 

[ianmoore]

The question isn't if the transom can hold the weight.. If it was properly rebuilt, it can... The real question is, does the boat have enough buoyancy to hold the extra weight.. Glaspar never gave a max weight, or a max hp in 1959 for the Sefair sdn. Likely because the boat could use all the hp that was available at the time and still need some..

I think a 90hp Suzuki is where you want to be. If you go to 115hp, you can do it at 400 lbs. They happen to be the lightest motors in their class, pretty much all the way across.. It would be 343lbs for a 90hp which is only 28 lbs heavier.. It will run like an old 100hp.

I rebuilt the transom myself, and it has held up well to this point. No stress cracks or anything to indicate any compromising of it. I relocated the batteries to the cuddy, got rid of the side saddle aluminum tanks and put my tank behind rear seats. I will look into the Suzuki.

 

[KJM]

Definitely looking into that. The Merc TOP 155 is 295lbs. The 4 strokes I'm looking at are 350-375LBS.
I'm Considering this as I look into different transom materials as well

I don't think the Coosa will give you extra strength, just the bonus of being rot proof. I rebuilt my transon with Thermlite which is basically the same thing and as far as the strength of the core material goes i'd say the plywood is likely stronger. However the Coosa is lighter and the most of your strength comes from the fiberglass, not the core. Since you already rebuilt it and I assume its not rotted since, I would leave it as is. If you were really concerned maybe you could add another layer or two of fiberglass to the inside of what you now have?