Evinrude 30 Too much fuel pressure??

[Bone1099]

Mid 90s Evinrude 30 with tiller handle.
My friend got the motor pretty cheap and the guy told him it would probably need the carb rebuilt but if something bad was wrong internally he would give his money back.
We rebuilt the carb put the muffs on started and ran so we took it to the test pond and after some minor tuning idle was acceptable. At wide open throttle it runs great also but just above 1/4 throttle is has a bit of a stutter but not really a dead spot just a bit more throttle around 1/2 open clears and runs smooth. During this stutter area i can manually choke the carb this makes it worse. Also i unplugged the clip on fuel line from the tank almost immediately all throttle settings improve and no more stutter. Float level right? So I adjusted the float to lower the level in the bowl. No improvement. Checked idle timing adjustment, linkage adjustment and condition, and max throttle timing all checked good. Lowered the level more no improvement. Returned float to proper level and still have stutter unplugging fuel line still fixes the problem. Is there any method for lowering fuel pressure or fuel pump output. Or just something i am missing.
Now I'm stttarting to stttuter and have no more hair please help.

 

[tashasdaddy]

Re: Evinrude 30 Too much fuel pressure??

do a link in sinc. it is getting too much fuel before spark. also check timing.

 

[Bone1099]

Re: Evinrude 30 Too much fuel pressure??

First I ordered the Jonhnson/Evinrude Service manual. Which clarifies the link and sync procedure much better than the clymer manual I had that really didnt cover the correct year model anyhow. Yes the link and sync was a bit out of rig. After checking and double checking the rigging everything seems great but the mid-range is still stuttering and missing. Idle is good although specified 650 rpm seems a bit high. Wide open throttle is great although from idle it bogs a bit before accelerating up to high rpm. After it gets there it runs great. Still if i unplug the line from the tank it runs great until it runs out of fuel.

A marine technician at a dealership sold me a fuel pump rebuild kit for a 115 Merc in the past. He opened the box pulled out the parts and instructions. Pointed out me in the instructions a couple of small parts (cap and spring I think) on each side of the diaphragm. He said "If you leave these parts out it will work better" we did and it worked fine. So my question is could this be relevant in my current situation? If someone in the past performed this "trick" on this fuel pump could that cause too much fuel pressure?
Maybe I am chasin' the wrong rabbit. Tomorrow im gonna check out the carb again and the fuel pump.

New at this but Im' willing to listen and a pretty good learner.

 

[petryshyn]

Re: Evinrude 30 Too much fuel pressure??

Problem is, you don't know if someone built this problem into the engine before you got it.

check for:

-wrong carb for application
-wrong jets or air bleed installed
-top cover warped
-slow speed needle valve way out of adjust
-modified or drilled transfer orfices

 

[Bone1099]

Re: Evinrude 30 Too much fuel pressure??

Checked P/N 's for schematic
All checks good
Carb P/N matches book
Orifices air and fuel are correct
Checked needle seat today couldn't make it leak
Checked fuel pump and found a couple of small holes in the diaphragm that are not supposed to be there so im gonna rebuild the fuel pump. I know it is contrary to anything that makes sense but i cant help but think that this may be my problem. I dunno we will see.

 

[F_R]

Re: Evinrude 30 Too much fuel pressure??

Checked P/N 's for schematic
All checks good
Carb P/N matches book
Orifices air and fuel are correct
Checked needle seat today couldn't make it leak
Checked fuel pump and found a couple of small holes in the diaphragm that are not supposed to be there so im gonna rebuild the fuel pump. I know it is contrary to anything that makes sense but i cant help but think that this may be my problem. I dunno we will see.

Well if the diaphragm is perforated, it certainly will dump extra fuel into the cylinder that drives the pump.

It is impossible by design for the pump to supply too much pressure. Pump pressure is a product of the pressure pulses in the crankcase, which can't be too high. But the air dome spring is an "accumulator", meaning it smooths out the pressure pulses. Don't be re-engineering it by leaving parts out.

 

[Bone1099]

Re: Evinrude 30 Too much fuel pressure??

Installed new fuel pump repair kit and it runs great retuned idle mixture and closed cowl. It makes much more sense that the fuel was entering the engine through tne fuel pump pulse port. Thanks guys