115hp outboard motor bored out to a 120hp

[joker]

What kind of problems if any will I have with a 115hp motor being bored out to a 120hp. This was done 3 years ago? Also, around how much would a stainless prop cost for this motor. I think it is a Johnson.

 

[JB]

Re: 115hp outboard motor bored out to a 120hp

"Bored out to 120 hp"??<br /><br />A disaster waiting to happen, unless you have again used incorrect terms.<br /><br />Get a good, stock engine of the hp your boat and usage call for. Stay away from home-made "hot rod" engines unless you are an experienced wrench, which I doubt.<br /><br />

 

[Deerdog]

Re: 115hp outboard motor bored out to a 120hp

Im no JB when it comes to expertise but I totally agree with what he says. Years ago we had a neighbor who had one of these "bored out" for extra horses motors. I believe it was a 150 evinrude supposedly bored and built to where it was supposedly putting out 170 hp (how they figured that I dont know). He spent most of the time admiring how nice the boat looked as it never seemed to run right. The local shop at the lake really didnt want to mess with it. He got rid of it that fall.

 

[singerjr]

Re: 115hp outboard motor bored out to a 120hp

Can't understand why anyone would need to "bore out" a 115 to a 120 when you can gat more than 5 hp with carb jets, performance reeds and prop.<br /><br />Sounds odd anyone would spend that kind of $$$bux for 5 horses

 

[G DANE]

Re: 115hp outboard motor bored out to a 120hp

I heard that kind of expressions before. Some people really think a motor gets more HP, grounded on the tiny increase in volume you get when you bore a powerhead and fit new pistons at a rebuild. It is because of lack of knowledge. Increasing volume without changing anything else wil probably give the same 0.020 HP as you increase volume when you bore. But of coarse, compared to running the damaged powerhead which were the reason for the rebuild, a gigantic increase is felt.

 

[flatskiff]

Re: 115hp outboard motor bored out to a 120hp

also consider when you bore a 2-stroke assuming thast what you have you completely change the port timing by lowering them and widening them. It takes professional work to get back to the proper timing. Then your exhaust needs modified but isn't really nessisary and I have no idea how you would do it with an outboard. I know ppl that take a 250 single 2-stroke with 45bhp and make it turn out close to 70hp with keeping the same bore.

 

[jwhite]

Re: 115hp outboard motor bored out to a 120hp

You don't change port timing just by boring. The intake and exhaust ports stay in the same place. The only time you change timing is when you open the ports up by cutting them bigger.

 

[joker]

Re: 115hp outboard motor bored out to a 120hp

I talk to the person that has the boat for sale and basicly the Charger, Chrysler 115hp was just overhauled and they had better performance. His son is the one saying it was bored out to 120hp. How good is the charger, Chrysler outboard motors. Is it easy to find parts for it. It is a 1981. The motor started right up and ran smooth with the muffs on. We will be taking it out hopefully this weekend for a test drive. What should I look for to make sure there is no hidden damage? How warm sould the water coming out of the pee hole be while running with the muffs?

 

[Forktail]

Re: 115hp outboard motor bored out to a 120hp

I would guess the motor was bored out for rebuild purposes, not performance gains. The owner probably thinks he picked up 5 hp, but he might have gotten just a couple through the increased displacement.<br /><br />Over-bores are common with high hour motors or worn cylinders. Most outboards have enough cylinder thickness to at least allow the first +.010 over-bore. The added bore equates to more air and fuel capacity in the cylinder which means more power.<br /><br />Exhaust and timing mods are not necessary for this. But a good over-bore will make sure that the exhaust ports are chamfered properly, and jetting is slightly increased. Of course new pistons and rings are a must.<br /><br />You always take a gamble with an older used motor, but if the rebuild was done properly it would be better than an unrebuilt older used motor.