HP limit for pontoon

[btwarren]

Can not find plate on a 1985 Polar Kraft 28 foot toon--currently has a 85 Force and looking to up grade to a 115 Honda . Cant find any info on this boat as the company has gone away Thanks for any help guys

 

[Rancherlee]

Re: HP limit for pontoon

Can not find plate on a 1985 Polar Kraft 28 foot toon--currently has a 85 Force and looking to up grade to a 115 Honda . Cant find any info on this boat as the company has gone away Thanks for any help guys

There is a Coast Guard formula for figuring out MAX hp on a pontoon. You need to figure out your Cubic Feet of flotation first, then multiply by length of the toons, then divide by the diameter of the toons. Personally I haven't seen a 25'+ pontoon that hasn't been rated for at least a 115hp.

Just a quick calculation with 23" log is showing ~170hp for a 28' toon, but its more that likely limited by the strength of the Transom pod and please note that the 480# Honda 115 is going to be a lot of weight on a transom designed for a 330# 115hp from 1985 and WILL need some reinforcements. Trust me, my 360# 70hp Johnsuki bent the transom of my 70hp rated old pontoon the first summer I owned it! the "OLD SCHOOL" 70hp engines were in the 220-250# range.

 

[steelespike]

Re: HP limit for pontoon

The Force is 249 lbs, a 2000 115 honda is at least 496,a 2000 Evinrude is at least 349.
Just assuming your doing used. If your thinking new the Honda is still around 490, the Evinrude Etec is about 405.
I mention the Etec because it is a direct injected 2 stroke that meets all CARB requirements.

 

[btwarren]

Re: HP limit for pontoon

There is a Coast Guard formula for figuring out MAX hp on a pontoon. You need to figure out your Cubic Feet of flotation first, then multiply by length of the toons, then divide by the diameter of the toons. Personally I haven't seen a 25'+ pontoon that hasn't been rated for at least a 115hp.

Just a quick calculation with 23" log is showing ~170hp for a 28' toon, but its more that likely limited by the strength of the Transom pod and please note that the 480# Honda 115 is going to be a lot of weight on a transom designed for a 330# 115hp from 1985 and WILL need some reinforcements. Trust me, my 360# 70hp Johnsuki bent the transom of my 70hp rated old pontoon the first summer I owned it! the "OLD SCHOOL" 70hp engines were in the 220-250# range.

Thanks for the insightful replay --You confirmed what i was thinking that that would be the weak point, I may drop back to the 90, that is at the max weight by your calculations. It will also be a grand cheaper. not sure that the extra 25 horses versus wight would be worth the extra work to fix motor bracket. I have already beefed it up with some bracing back there due to some flexing. Im not looking to go fast just want it to be very dependable. I have removed all the furniture and she rides high out of the water. does have a hard top though.

 

[btwarren]

Re: HP limit for pontoon

The Force is 249 lbs, a 2000 115 honda is at least 496,a 2000 Evinrude is at least 349.
Just assuming your doing used. If your thinking new the Honda is still around 490, the Evinrude Etec is about 405.
I mention the Etec because it is a direct injected 2 stroke that meets all CARB requirements.

Thanks for the reply. I am going new and am thinking I may drop back to a 90 due to weight issue. It will save me a grand on the price also. I looked into Etec also but after much research I decided on Honda. Its takes a lot of brain power to figure all this out lol -I may have to go fishing to ease my mind.

 

[muskiemike12]

Re: HP limit for pontoon

A 115hp Merc weighs #399, man that Honda is a heavy beast!

 

[Bamaman1]

Re: HP limit for pontoon

Weight's a consideration when buying a Honda. You know they're of high quality and dependable. That reputation has unfortunately hurt their retail sales.

You may see if a local welding shop can beef up your transom. You have a long boat and it will handle the weight if the rear end is strong enough. New motor pods are available online if you Google "pontoon kits."

My 1985 Starcraft 24' has a Yamaha 115 hp 2 stroke, and it'll accelerate like a bass boat until hitting a mph wall at around 25 mph.

 

[calvinator]

Re: HP limit for pontoon

For reference, I have a 29' 1989 pontoon with 23" logs. The transom is all aluminum, welded, with gussets. My transom rating is 125HP.

If you have a similar transom, then you are probably rated for a higher HP motor - 125HP probably being the max.

I have seen transoms of this vintage pontoon that are just marine plywood bolted to the transom and their ratings were 75-90HP.

 

[Rancherlee]

Re: HP limit for pontoon

He does bring up a good point, if your transom only has doubled up 3/4" plywood with no backing plate/bar a 115hp engine is pretty iffy. I welded in 3" aluminum C channel across the transom on mine that the upper mounting bolts now go through. If your willing to spend the bucks on a new Honda you might as well look into a new transom pod for 500-600$ or go all out and find a "scratch n dent" 3rd log with an integrated transom for ~1500$ and upgrade the toon for modern performance if your mechanically inclined to do so!