Performance Modifications

[JasonM1955]

I have a 1977 115 Evinrude and was wondering are there any engine modifications you can do to increase the horse power out of this motor?<br />Thanks:<br />Jason

 

[JasonM1955]

Re: Performance Modifications

Hey Brian,<br />Thanks for the info. The motor is in great shape, it was rebuilt about a year ago and all new stuff was put in. With a 19" S.S. prop I'm turnng about 4900 at w.o.t. which I don't think is enough. What do you think?<br />Thanks again:<br />Jason

 

[gw204]

Re: Performance Modifications

On a 25 year old engine, I'd first make sure it is in PERFECT shape. Good compression, new water pump and thermostat(s), new plugs, new fuel pump and fuel lines, timing set, etc., etc.<br /><br />After that, make sure you are trimming it properly. Is it propped right and is the prop in good shape? What rpms are you turning at wide open? Is the hull of the boat clean? Barnacles and scum will kill performance.<br /><br />Only after you have checked/corrected any of these issues should you look at upgrades. Else, you may be throwing money away.<br /><br />Check out Boyesen Power Reeds (www.boyesen.com). I've not used them but they sound good. That's really the only upgrade I know of.<br /><br />Good luck.<br /><br />Brian

 

[Dhadley]

Re: Performance Modifications

As mentioned in a reply to your other post, you are off in RPM's by 1000+. If your motor was rebuilt and has been lugged for a year it is not in good shape. Most likely the bottom rings on the starboard side are coked up. If they are coked badly they are on the verge of breaking. Especially if the wrong spark plugs are being used. <br /><br />Verify the tach is set on position 6.<br /><br />Do a compression test. If the motor is indeed OK then decarbon it. Once that is done you can start to play with the X dimension. Write down all your stats now including water pressure. Try raising your motor. Your R's should come up along with performance at all levels.<br /><br />Keep us posted!

 

[JasonM1955]

Re: Performance Modifications

Dhadley,<br />I will do a compression check tonight. What kind of compression should I have with this motor? How is the best way to decarbon the thing?<br />Thanks for all advice guys<br />Jason

 

[JasonM1955]

Re: Performance Modifications

DHadley,<br />I really appreciate all of your info. I do have one more question. What is the highest timing I can run on this motor without getting into burning a piston? I always run 93 octane gas in it if that matters.<br />Thanks again:<br />Jason

 

[Dhadley]

Re: Performance Modifications

As long as the compression is within 15 lbs high to low you are OK. If it's not, don't panic. There may be a couple of things to look at.<br /><br />Stop by a J/E dealer a pick up a can of Engine Tune. You want the one with a spray nozzle, not the hose. Follow the instructions on the can. DO NOT let it sit in the motor longer than instructed.<br /><br />Good luck!

 

[Dhadley]

Re: Performance Modifications

Yes that matters a lot! DONT! 87 is fine and is all that is needed. Higher octane with todays fuel will result in higher combustion temps. Check your timing at WOT now and let us know what it is. Dont change that yet. Also make sure you are using Champion plugs.<br /><br />Good luck!

 

[JasonM1955]

Re: Performance Modifications

Dhadley,<br />I checked the cranking compression tonight and I had 3 to check 150# and one checked 145#. Does that sound ok?<br />Jason

 

[Dhadley]

Re: Performance Modifications

Thats perfect. Now we can check the timing and see where its at. Make sure you have Chompion plugs. I would use the L77JC4's or QL77JC4's.<br /><br />Do your sync and link visually. Butterflies all the way open and timer base aginst the stop. This visual can be done without the motor running. <br /><br />When you back the boat down the ramp to do the timing, run the light over all 4 wires to make sure they are all firing at or near your 4900.<br /><br />Make sure you always use fresh 87 octane and good oil.<br /><br />Let us know what you find!