Repowering 23.3' 1973 Tsunami

[mike c]

Does anyone know how much weight the transom will take? Thinking of putting a pair of new 150hp Mercury fourstrokes on. I currently have a pair of 175hp Mariners on it now.

[Capt Terry]

mike c-
I realize your question is about transom strength. I don't have an answer for that. However, you may be interested in my post of a few minutes ago to you & Offshore Asset on a tool to estimate CG shift. With it you can judge if the heavier engines will adversely affect you. Best wishes.

[McGillicuddy]

Originally Posted by mike c

Does anyone know how much weight the transom will take? Thinking of putting a pair of new 150hp Mercury fourstrokes on. I currently have a pair of 175hp Mariners on it now.

Attachment 13491

Welcome aboard Mike,

Good to see another 23 on the left coast. I think the biggest outboards available when your boat was built were merc 150s - under 300 lbs. By mid 70s the v6's came along and brought 200s in the 350 lb range. I'm guessing yours are 400 lbs or so if newer tha 89 or so. 800 lbs or so. Your looking at adding another the 120 back there so make sure your transom is stout.

You'll probably wanna check transom for rot and moisture before you buy.

I don't know that there is a weight rating for these transoms although i'd bet someone has conducted some tests out of curiosity.

Have you considered a big single?

cheers and good luck.

[Bigshrimpin]

Nice find out there!! Those 175's are 20" shaft 2.4L engines (probably 1983 or 1984 by the looks of it) on an original 25" transom. They weigh in at 363lbs each. I wouldn't move up to four stroke 150's (455 - 470lbs) without raising the transom to 30". Twin 115 Mercs four strokes are about the weight of what you are taking off now. I still would strongly consider rebuilding the transom to 30" (for twin 25" shaft 115's) or at the very least thoroughly inspected before committing to any repower.

This is my boat running with one of those 80's 175 powerheads on a 2001 25" Mid. I blew it up this year : ( after running through a sandbar. I can't complain too much that motor was running continuously pushing my 18 in 2009 + 2010 and then the 23 from 2011 - 2015.

https://www.youtube.com/watch?v=jg7cdv1w1vE

[Bigshrimpin]

off topic, but I thought you might appreciate the picture.

Here's a nice Ad with Ralph Delph's 20 seacraft "Vitamin Sea" with the same vintage Mariner. RIP

http://www.legacy.com/obituaries/boz...&pid=177712239

[kmoose]

I know there seems to lot of concern on putting 4 strokes on our hulls. It's a real issue in some cases but not so much with Tsunami/Sceptre configurations. I would however consider a big single over a twins with the 4 stroke option. Aside from less combined weight per HP, a single lower unit is much more efficient in a hydrodynamic perspective. I would think you would have to go 175s to get the performance of a single 300.

[Vezo, Part II]

That pic is kind of deceiving, Not. The tops of the engines are flush with the transom! In 1996 I blew the 200 Mercury (What did they call those back then?), which was rigged with a new head gasket for the sea trial. Rebuilt it twice to no avail. In 1999, I believe 3 years before Jason started this site, I repowered with a 1999 Johnson 175 carb, and immediately went pre-mix. Also had transom redone, however NO one had ever suggested going to 25". What a shame.

Vezo

[ericallen01]

Nice boat! Can't deny the twins are a nice set up - my 2.5s are 25" (XL, port CR) and from 1993 pretty much indestructible though wouldn't mind the EFIs to get better mileage.

Note I rebuilt my transom a while back and added stringer bracing + an extra piece of marine ply behind my bracket. The ride is stiffer now. If you're rebuilding a transom worth considering.

The boat originally had twin 165 I6s before the last owner converted it.

Today I'd probably trade for a 30" Yamaha 300 and a kicker.

Good luck!

[bgreene]

Originally Posted by Bigshrimpin

Nice find out there!! Those 175's are 20" shaft 2.4L engines (probably 1983 or 1984 by the looks of it) on an original 25" transom. They weigh in at 363lbs each. I wouldn't move up to four stroke 150's (455 - 470lbs) without raising the transom to 30". Twin 115 Mercs four strokes are about the weight of what you are taking off now. I still would strongly consider rebuilding the transom to 30" (for twin 25" shaft 115's) or at the very least thoroughly inspected before committing to any repower.

This is my boat running with one of those 80's 175 powerheads on a 2001 25" Mid. I blew it up this year : ( after running through a sandbar. I can't complain too much that motor was running continuously pushing my 18 in 2009 + 2010 and then the 23 from 2011 - 2015.

https://www.youtube.com/watch?v=jg7cdv1w1vE

Sent a PM to you.......

[GameOnSalmon]

Mike i just bought a Sceptre with a 300 Zuke on it. The power is Perfect for this hull IMHO. There's a lot of other guys on the forum who have repowered with the 300 ZUKE and they Love it.

A big single seems to be the winner...
Robert