140 evinrude,, distance from doersel fin to keel

[dcolpitts]

I have a 140 evinrude on a 17' mako center console. I have a problem with idle speed over 10 minutes at a time. It loads up and foul plugs, the jetting is correct. I think the engine is to low on the stern of the boat, whitch would cause exsessive back pressure. From the water line to exsaust ports is only 4" and thats in calm waters and not in reverse. the boat has a jack plate on it so I can raise it . My question is from the keel to the dorseil fin what is the distance or rule of thumb

 

[roscoe]

Re: 140 evinrude,, distance from doersel fin to keel

The bottom red line in this picture (anti ventilation plate), should be even with the bottom of the boat.<br /><br /> http://www.iboats.com/ref/shaft_length.html

 

[Solittle]

Re: 140 evinrude,, distance from doersel fin to keel

I doubt that your problem is back pressure. What plugs are you using? Suggest that you test your ignition system with a spark testor. And do you know if your timing is on the mark?

 

[dcolpitts]

Re: 140 evinrude,, distance from doersel fin to keel

Spark plugs are Champion QL77JC4 gapped at .040, good 1/2" spark gap, all electronics have been tested, Compression 115-125psi, Anybody have any ideas I may have overlooked?

 

[Solittle]

Re: 140 evinrude,, distance from doersel fin to keel

I'll throw out one more idea - Have you removed the thermostats? I had an idling problemwith my twins which was partly caused by a mechanic cutting the cores out of the Tstats some years prior. The temporary fix was to raise the motors a bit when idling. This changes the float level in the carbs which changed the fuel flow slightly. The fix was new thermostats.

 

[Forkin' Crazy]

Re: 140 evinrude,, distance from doersel fin to keel

I bought a 150 a while back that was doing the same thing. Float levels were too high, causing a rich mixture. Hope this helps.<br /><br />FC

 

[crazy charlie]

Re: 140 evinrude,, distance from doersel fin to keel

Okam,I have the exact set up that you do.Mine is early 80s.Your problem is not back pressure.i would look elsewhere to solve your problem.Charlie

 

[AUGIDAWG]

Re: 140 evinrude,, distance from doersel fin to keel

When you say "raise the engine" at an idle, you do mean "tilt" the engine up, correct?<br /><br />Does this lower the gas level in the float bowls, and therefore lean out the idle?

 

[dcolpitts]

Re: 140 evinrude,, distance from doersel fin to keel

Ok, thanks for the reponses. I checked the timing saturday, was 3-4 degrees retarded. changed the timing to factory specs(18btdc) ran ggreat high rpm, 5800 top speed trimit out almost 6000. midrange the same as before slow out of the gates but good up and down after the start from idle. Idle was much better with the timing change, had to slow it down( was idling to high. The only differance was it started out misfiring at idle, just a pop on the exshaust every minute. after 1 hour of slow running and high speed mixed running lost the slow speed(below 1300rpm and would loose a cylinder and would stall) if increase in rpm"s with the throttle it would clear out and take off. you could see fuel oil mix smoke. Background info, new vro. power pack, charge coils, complete check on electrical. Totaly rebuilt carbs (2X"s). The only thing I didn"t do was change plugs after timing and jet change to factory settings after the timing change. the only other thing that might effect the igntion would be that I replaced 2 cyl with auto type plug wires, it still tested out with a 7/16 spark on the gap test. Good luck all this has me stumped. I will change the thread on the 22"d if I don"t get any replies. Thanks for replies as always.

 

[93bronco]

Re: 140 evinrude,, distance from doersel fin to keel

i stand to be corrected.<br />-<br />but i think you have to use a solid core wire.<br />most common auto wires are silicone core.

 

[dcolpitts]

Re: 140 evinrude,, distance from doersel fin to keel

forgot to mention that the motor is on a jack plate.(flyweel is is in a level postion on any trim except for launching and take outs)