Powering DOWN 115HP Johnson to 90HP

[UpstNYer]

My boat is has a max HP rating of 90HP. Local dealer is offering a new 2002 115HP Johnson at a good discount. Comparing specs. on new Johnson's, the 90 and 115HP have same piston displacement and weight. The 90 appears to be simply a detuned 115. <br /><br />Don't want to overpower the boat...I can make a mess of things fast enough without doing that. But can the 115 be simply & economically detuned to 90HP so I can take advantage of the discount? Any long-term ramifications of doing so? Thanks.<br />Bob

 

[UpstNYer]

Re: Powering DOWN 115HP Johnson to 90HP

Oh yeah, forgot to mention: two-cycle, carbureted.

 

[Solittle]

Re: Powering DOWN 115HP Johnson to 90HP

Your boat should handle it readily - - here is the BUT - - To find out the ramifications call your insurance company and ask them if they will stand behind you if you have an accident that involves damage to someone's property or injury when you knowingly put an engine on your boat in excess of the max rated power by the manufacturer. I bet you can guess their answer.

 

[walleyehed]

Re: Powering DOWN 115HP Johnson to 90HP

Drop your WOT timing 5 degs. if it's THAT important..........

 

[UpstNYer]

Re: Powering DOWN 115HP Johnson to 90HP

SoLittle, you make a point I hadn't thought of...not so much the insurance angle, but the hull warranty. It would probably be voided regardless of what was done to reduce engine output. If manufacturer found out a 115 was used on it, the warranty would be out the window without any consideration of the state of tune.<br /><br />Actually I'd prefer to just leave it a 115 and just not 'get on it'. Probably wouldn't anyway as I scare easy. <br /><br />A detuning tip was what I was originally looking for; so thanks Walleyehed.<br />Bob

 

[BRWGL1800]

Re: Powering DOWN 115HP Johnson to 90HP

Will a 90 engine cover fit on the 115? That is what I would change if anything. I would be leary of going over the rating though. I have a boat rated for 140, and a 150 would rock, but I could get into a lot of trouble for that one. Not many 140s out there.<br /><br />Brent

 

[Hooty]

Re: Powering DOWN 115HP Johnson to 90HP

Put the 115 on and forget about it.<br /><br />c/6<br />Hooty

 

[SeaMasterZ@aol.com]

Re: Powering DOWN 115HP Johnson to 90HP

hooty is right, 115 is optimal hp, temp humidity, fuel quality, state of tune (granted, a new one SHOULD be tuned perfect, but Monday Motors happen)<br /><br />a strong 90 and a doggy 115 are likely close in terms of real world output, also remember that with boats you have hydrodynamics at play, 20% increase in power only means 2 - 5 % increase in top end - since I suck at math, Ill let someone else explain it, but for now, get the 115 and fuggetaboutit<br /><br />