Need info on maxing out the transom

Nismospeed

Seaman Apprentice
Joined
May 14, 2009
Messages
44
Ok, I am about to get my tail handed to me, but Im ready for it. I have been reading through some different sites and the recent threads here about what a good size engine would be for various pontoon lengths. I read that a decent motor for a 24' pontoon would be the 75-90hp range. Cruises nicely and can pull skiers and what not. Sounds fair enough and accurate. HOWEVER... I just bought a 24' play liner with a 50hp Merc o/b and was considering upgrading it to something a little beefier. I got to looking at the max cap rating plate and almost cried when I saw 60hp max. Is this rating based on safe operation or tearing the pontoons out from under the deck? Can the transom not handle anything over a 60hp? I was just curious. A guy called me today offering me a 200hp Black Max for my van, and thats what got me thinking. Obviously, I considered putting it on there, BUT, I thought that might be a tad-bit extreme and was thinking about trading it off for a 115hp-140hp. What can the transom and boat take before I twist the transom or shred the pontoons? My oldest LOVES tubing at higher speeds. I believe I have the 25" pontoons, and they are the thicker aluminum, as this is a '94 model. Ok, now you can point, laugh, whatever.... but PLEEEASE leave some useful feedback or advice after you are done smiling. Thanks!!!:D
 

Boss Hawg

Lieutenant
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Apr 9, 2009
Messages
1,433
Re: Need info on maxing out the transom

All i'll say is i just installed a Johnson 110 on my 20' Sun Tracker that reads rated for 90hp :rolleyes:
Now i did install a new "bit beefier" transom while i was at it :)
 

Nismospeed

Seaman Apprentice
Joined
May 14, 2009
Messages
44
Re: Need info on maxing out the transom

Thanks Boss... what kind of speed are you pulling with that 110? and where did you get the transom from?
 

5150abf

Vice Admiral
Joined
Aug 12, 2007
Messages
5,808
Re: Need info on maxing out the transom

Try this, if you could hold a max of 100lbs over your head and I put 140lbs on the bar what would happen?

You could probably hold it for awhile then it would crash down on your head, it is the same with the transom.

It isn't a question of if but when it will fail and it normally happens at full throttle so you have a motor running 5000 rpm attached to a few cables, not good at best.

A pontoon is different than a regular boat too in that the motor pod is screwed or bolted to the boat so those bolts handle all the stress.

I build pontoons for a living and can tell you that number is there for a reason.

If you want to do this look into getting a different motor pod that is rated for what you want to put on the boat, all aluminum would be best.
 

Boss Hawg

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1,433
Re: Need info on maxing out the transom

Thanks Boss... what kind of speed are you pulling with that 110? and where did you get the transom from?

Just got the "new" motor bolted & mostly wired & rigged yesterday-
The transom was still strong (just ugly) so i just replaced "glued 'n screwed" marine grade 3/4" plywood same as was on it. Also has a peice of 1/4" steel plate across the total width of upper half that i of course re-installed "just because":rolleyes:
The boat came to me with a 115 already mounted but had too many issues :(
 

lakegeorge

Senior Chief Petty Officer
Joined
Mar 19, 2002
Messages
660
Re: Need info on maxing out the transom

I wouldn't do it for several reasons,

Other parts of the boat may not be made to withstand the stress & vibration at higher speeds.

Insurance purposes.

How would you feel if your towing someone and the thing breaks apart and injures them, probably not very good.

Sorry that I can't leave you any wiggle room, I'm just being honest.
 

jusfloatin

Petty Officer 1st Class
Joined
Jan 6, 2008
Messages
295
Re: Need info on maxing out the transom

Years ago I put a 350 Chev into my Vega. It did take a while but cracks soon appeared. We did try to repair the cracks and beef up the frame but the problem was/is that we did not do this before installing the motor.
We got anouther Vega and did beef up things prior to the installed a rebuilt 383 stroker. This car showed no signs of stress right up to the point where it hit retaining wall.

I guess what I am trying to get across and this is just my opinion is that you could install a motor so big it almost swamps the boat but as long as the transom the motor hangs onto is the deck itself you will have problems. This is a fact.
You need support from the pontoon frames themselfs to make it last. How long it would last depends on how much of the pontoon frame you utilize.

I am working on a 19' pontoon which with a little luck will be faster than most runabouts.

As for the Black Max- chicks dig scars and no guts no glory
 

KStoon

Seaman
Joined
Aug 31, 2009
Messages
56
Re: Need info on maxing out the transom

A toon would not be my first thought if I wanted a ski boat or wake boarder. Power, speed, maneuverability most toons are not. But...for just pulling a tube that's something I've thought about on mine. I have a 85hp on a 20' with a tagged rating of 90hp max. It cruises along fine but it's not too exciting especially when friends circle you on their jet skis as you cruise along. Add the drag of a person/tube I'm sure my speed would diminish. I agree the ratings are there for a reason. As a package that is what the boat is safely operated with. I'd bet there is a margin for error figured in to account for the person who wants to push it some.
 

Boss Hawg

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Apr 9, 2009
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1,433
Re: Need info on maxing out the transom

I belive HOW you're going to use it makes a big difference too-
Personally if not for the shear weight problem i could put a 300 hp on mine & be just fine the way i run a boat :rolleyes:
I DO NOT care about speed per say- If i'm going to a fishin hole i go at a nice casual speed - If the wife & I are just cruising around the lake again i just cruise around at a rate that suites me :)
The only thing i pull behind my boat is the anchor along the bottom when i forget to pull it up :redface: :p
 

Nismospeed

Seaman Apprentice
Joined
May 14, 2009
Messages
44
Re: Need info on maxing out the transom

I belive HOW you're going to use it makes a big difference too-
Personally if not for the shear weight problem i could put a 300 hp on mine & be just fine the way i run a boat :rolleyes:
I DO NOT care about speed per say- If i'm going to a fishin hole i go at a nice casual speed - If the wife & I are just cruising around the lake again i just cruise around at a rate that suites me :)
The only thing i pull behind my boat is the anchor along the bottom when i forget to pull it up :redface: :p

niiiiiice. Well, from what I am reading, I could essentially drop a 140hp on mine, provided I reinforce the transom, add brace points to share the stress, and dont "gun it" while im out. I have to agree on usage. I plan to do a lot of gentle cruising for the most part, but there will be points during the day where the kids will be begging me to drop them on the tube. And if it rains, I know wife will be asking for the quickest speed/route possible. Our little 50hp just wont save the day. Like I said, I dont really want to switch to the 200hp, but I was wondering if it was possible to exceed my rating without wasting the pontoon itself. Also, I read that the USCG wont bust you for exceeding, as long as the craft exceeds 20'. Is that about right?
 
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