Motor Size

[onlyjohnson]

This is my first post and I am not sure if this it the correct forum.

I have a 20ft pontoon boat that has a Johnson 50hp. The boat is rated for a 100hp max. I have been given a 115hp motor for free and it runs great . What type of problems could I have if I put the 115hp on this boat?

Current motor is a 1993 Johnson 50hp. The new motor is a 1998 Johnson 115hp.

Any advice would be great.

 

[Scaaty]

Re: Motor Size

Wouldn't bother me one bit, but run it by your INS agent first...

 

[tashasdaddy]

Re: Motor Size

i agree, just be very carefull, as it will be consider overpowered, in court. the weight of the 2 motors, 100-115 is very close of the same, so the boat should handle the engine weight with no problem.

 

[steelespike]

Re: Motor Size

Be aware the 50 will use about 5 gph(Gallons per hour) at wot(Wide open throttle)the 115 about 11.It will no doubt change the way the boat handles,rides and floats.The 50 will do about 20 mph.the 115 27 or 28 using a lot more gas.You will be able to cruise at 20 mph and the 115 will be loafing.
using about the same gas as the 50.Be sure the 115 is the correct shaft length.

 

[dimock44]

Re: Motor Size

In Texas you can't (leagally) sell a boat with an oversized motor. I guess it might be the same in other states. I would do it any way.

 

[rndn]

Re: Motor Size

You really shouldn't overpower a boat. Boats are designed to handle the rated HP and no more.

 

[Kenny1970]

Re: Motor Size

You can buy a bolt on transom rated for more horse power.
I was doing some thing like this a long time ago and found them on Ebay for 150 to 300 dollars.If I could do it all over again I would not.
I spent close to about 1000 dollars to make mine become a gas hog with not much more speed.
I sold it and got a bass boat after it was all done.

 

[boatsplusoutboards]

Re: Motor Size

hi there
the weight seems ok i think it would handle it well.But it is over powering the vessel you may face legal implications.

 

[onlyjohnson]

Re: Motor Size

Thanks for all of your imput. The shaft on both motors is 20?. The transom on the pontoon boat is all aluminum.

Now my next question, Can I do this myself or have someone else change out the motors?

 

[tashasdaddy]

Re: Motor Size

the hardest part will be getting the new motor set to the right height, i would start where the 50 is mounted seeing the are both 20 in shafts, if the electrical plug match, it should be plug and play, controls should be compatible. you may want to change your helm to a no feed back helm with the larger motor. there was a change on the electrical harness, if different the is a convertion kit available.