140 Evinrude High Performance Questions

[HotRude]

I have 1985 140 Evinrude with a rebuilt 1988 140 big bore power head, Boysen power reeds, intake and carbs off a 1988. I used the heads off the 1985 (higher compression) than the 1988 heads. I've got 150 psi on all cylinders. Is this too much? I am concerned about pre-ignition. Should I retard timing? If so, how much? I am set at 17 degrees BTC now.<br /><br />On props, what would you recommend in a 4-blade prop?<br /><br />About how much rpm will I lose in a 4-blade 20 pitch prop versus a 3-blade 21 pitch prop?

 

[JB]

Re: 140 Evinrude High Performance Questions

Ahoy, HotRude.<br /><br />Anyone who can help you with props will need to know what boat you have your engine on, how much setback, if any, and your X dimension.<br /><br />You might get some help on the engine here, but it is more likely that you will need to find a site for racing outboards. I suggest you try Google.<br /><br />Good luck.

 

[Hooty]

Re: 140 Evinrude High Performance Questions

Yo 'Rude<br />Check this out.<br /><br /> http://www.screamandfly.com/ <br /><br />c/6<br /><br />Hooty

 

[HotRude]

Re: 140 Evinrude High Performance Questions

Thanks guys. I will give them a try.

 

[DB.Beachum]

Re: 140 Evinrude High Performance Questions

Yes I would come off the timing 2-4 degress using the small chamber heads and make sure you use 90+ octane,make sure cooling is at a premium because it is go to want to build heat,You will have better performance with 3 blades,and you will find you will have better selection in the performance prop area

 

[DB.Beachum]

Re: 140 Evinrude High Performance Questions

On my '84 140 s model,I also used the Boyesen reeds, matched the exhaust wedges, ported polished intake(removing all excess material)rejetted carbs,drilled the lower unit 4/ 7/16" holes so it idles quiet but it gave it another 100 RPMs at top end which put me into 1 size bigger prop

 

[HotRude]

Re: 140 Evinrude High Performance Questions

Thanks DB. I Think I will put the lower comp. heads back on, better safe than sorry.