1985 8 hp evinrude

[hunter4795]

I'm lookin for someone who might information on how to increase the horsepower from a 8hp to maybe a 10hp evinrude.[*]null

 

[CAPTBLACKSMARINE]

Re: 1985 8 hp evinrude

HUNTER YOU CAN CHANGE THE 8 H.P. TO A 10 H.P. THOUGH I HAVE NEVER TRIED ONE OF THIS SIZE ,I AM NOT SURE OF THE DIFFERENCES .BUT I CAN TELL YOU FROM RUNNING BOTH OF THESE ENGINES IT IS NOT WORTH THE TIME OR EFFORT .THE DIFFERENCE YOU SEE IN POWER IF AT ALL NOTICABLE WILL BE VERY MINIMAL.I AM QUITE SURE THAT THE CARB JETTING WILL BE DIFFERENT AND QUITE POSSIBLY EVEN THE PORT TIMING .(NOT THE SAME AS IGNITION TIMING).BUT AT ANY RATE IT IS STILL NOT WORTH THE TIME AND EFFORT TO DO SO.

 

[CAPTBLACKSMARINE]

Re: 1985 8 hp evinrude

P.S. 2 H.P. JUST AIN'T WORTH IT !

 

[jegervais]

Re: 1985 8 hp evinrude

Capt Black is right on, it ain't worth it. The 8 hp block powered the 5/6/8 models, with the 8 being the ported one. There are intake manifold, carburetion and exhaust differences too. The 1985 10 hp model used a larger displacement block, so you would have to "hop up" the 8's block to get anything more. That's a rather pricey option and whether you could actually get the 2 hp out of it is hard to say...<br /><br />-John

 

[MOTION LINE]

Re: 1985 8 hp evinrude

If you have a look at the displacement difference between 8 and 9,9 models you will figure out that they are different as well as the whole construction, and as a matter of fact the 8 is actually improved (not soundvise) from the old trusted 5,5-6 hp. engine. The factory has already "hoped it up". If it is possible to do? I would guess you will never get 10 hp. out of it but on the other hand to make it run better is not an impossible task. One thing you can easily do if you have the equipment resize the main jets to meet the standards of the present gas, the engine will run better, at least mine did. You can also change the reeds to fiber reeds which often gives better throttle response and acceleration + less noice.
Theese changes can give you max 1 hp. which is noticeable on such a small engine
One thing you should not even try is tampering with the powerhead itself, you will probalbly only ruin it.
Rigging the engine higher on the transom can give more speed and improving the propeller all theese changes need a lot of work and you will not see an dramatic improvement, if it is worthwhile is up to you to decide. I have tuned many engines and have never thought on how much it cost only needed a better engine but for ordinary people I would recommend staying away from it.

 

[CATransplant]

Re: 1985 8 hp evinrude

That 8hp is already about as much hopped up as it can go. Nice little engines, but you aren't going to get any more out of it.

If you look at the 9.9 of that year, you'll see that it's a completely different engine than your 8. In fact, the same basic engine, with considerable changes, is also sold as a 15 hp.

Enjoy your 8 for what it is. If you need more power, sell it and buy a larger outboard. Messing with your nice 8 hp will just ruin it.

 

[MOTION LINE]

Re: 1985 8 hp evinrude

I aggree that tampering with the 8 will probably ruin it, that is what usually happens but after makeing a quick search couldn?t resist trying my 15 hp. carb on the 8 hp. (1/3 bigger dia + bigger jets othervise the same) bolts right on. Guess what happened, did it go faster and work well over all?
The boat went 15,3 knots before.

 

[Vic.S]

Re: 1985 8 hp evinrude

Just to put some numbers into it:

The 5, 6 & 8 hp engines are 164 cm? capacity (sorry don't know what that is in cubic inches, or what ever archaic units you folk use) the 9.9 and 15hp engines are 216 cm?.