Evinrude 75 hp WOT hesitation

[oldyota]

Alright I have old 75 hp Evinrude and it wants to die when start to give it throttle, so I push the choke button and it picks back up... Then when I have it on plane and give it full throttle and is surges back and forth, but at 3/4 it runs like a top.. I just got done tearing the carbs apart and cleaned them thoroughly, it seems that its not getting enough gas hence the reason I choke it and it rev's up like normal.... Am I needing to replace the diaphragms in the carb? Any advice would be greatly appreciated....

 

[jtexas]

Re: Evinrude 75 hp WOT hesitation

how old? need to know whether it's got choke plates or primer.

 

[oldyota]

Re: Evinrude 75 hp WOT hesitation

Its a 1976 Evinrude, push button choke on the key...

 

[tashasdaddy]

Re: Evinrude 75 hp WOT hesitation

did you do all the steps here? http://forums.iboats.com/showthread.php?t=244013

is the vent open on the fuel tank? is the bulb collasping, not going soft, collasping? does having someone pump the bulb help the motor pick up?

 

[jtexas]

Re: Evinrude 75 hp WOT hesitation

assume you meant fuel pump diaphram? answer to tash's questions will help.

Did you link & sync per the manual? also make sure the timer base moves without sticking.

Did you install new carb kits? (gaskets, o-rings, float valves & seats)

I'd check my floats - could be one or two are adjusted too high. Put a float in upside down once - you'd never know it till exactly 20 seconds after you put the hammer down, it'd start coughing. Timed it with a stopwatch. Any other throttle setting, pump kept up with demand.

How I discovered it was, blowing through the carb fuel inlets - too much resistance on one of 'em. Highly recommend draining the carb bowls first. Premix is an acquired taste.

 

[parrfive]

Re: Evinrude 75 hp WOT hesitation

I would clean them again. Almost any time choke is needed to obtain full throttle you have a lean condition. Be sure to clean the low speed tube as well. A thin piece of wire should do the trick.

 

[oldyota]

Re: Evinrude 75 hp WOT hesitation

So re-clean them and sync them up.... Hopefully I can get to that tomorrow and take a test run on Saturday....

I checked the bulb when I stopped and checked everything out.. So what would be the cause of the bulb getting soft and loosing pressure? I have a new tank and new fuel line and bulb, I did notice I had a fuel leak on the fuel filter when first rebuilt the carb, looked like the plastic cover was warped alittle and I took it apart and got it re seat and it stopped leaking... But that wouldn't be the problem with having to choke it at idle and low speed would it??

Again thank for the advice,

The oldyota

 

[parrfive]

Re: Evinrude 75 hp WOT hesitation

The soft bulb could be that one of the carbs is letting fuel by. If that’s the case you ether have a float level problem or carp between the needle and seat. The idle problem is most likely the low speed tube isn’t clean enough.

 

[Relliott]

Re: Evinrude 75 hp WOT hesitation

Check the Fuel Filter. You could have some trash in the filter. An inexpensive fix if it works.

 

[savvyauto]

Re: Evinrude 75 hp WOT hesitation

I have the same motor, same problem. I took the fuel pump apart and found a broken piece. New pump on order.

 

[oldyota]

Re: Evinrude 75 hp WOT hesitation

well if anyone is still interested in this thread I have an update.

Well after re-cleaning the carbs it still surged back and forth at full throttle, so I took it to my boat mechanic, after troubleshooting the problem he found that the power pack was working sometimes and then it would cut off spark to the 3rd cylinder. He just happened to have an extra power pack sitting around and put it on and wha-la she cruises now..... So after rebuilding the carbs, new plugs, used power pack, new impeller and an over all tune up he charged me $350, let's just say I'm pretty happy...

I forgot to mention that I got the motor for free and so now I'm $450.00 into it and boat was given to me as well... Not too bad to be fishing again in my boat..

Thanks everyone for your previous responses..