1975 evinrude 40 hp 40555c

[redssteelers]

Good day everyone, Bought a pontoon boat with a 1975 evinrude 40 hp 40555c. The motor doesn't like to idle at low rpms. I changed coils, both were cracked. Then I changed fuel lines, bulb and put on a new tank. Also replaced water pump. Nothing has helped. Put new plugs in - same thing. Checking on the evinrude site the plug that I replaced j8c is not the correct plug. UL81C is the correct plug. Would changing the plug help with the idleing issue. Thanks for any help. Once the boat gets to about 1200 rpm and above it purrs like a kitten. Will push the pontoon boat along at 19 mph. James

 

[tom_wise]

Re: 1975 evinrude 40 hp 40555c

Good day everyone, Bought a pontoon boat with a 1975 evinrude 40 hp 40555c. The motor doesn't like to idle at low rpms. I changed coils, both were cracked. Then I changed fuel lines, bulb and put on a new tank. Also replaced water pump. Nothing has helped. Put new plugs in - same thing. Checking on the evinrude site the plug that I replaced j8c is not the correct plug. UL81C is the correct plug. Would changing the plug help with the idleing issue. Thanks for any help. Once the boat gets to about 1200 rpm and above it purrs like a kitten. Will push the pontoon boat along at 19 mph. James

Hi James,
It's doubtful that changing the plug to spec will change your idle issue, but it's always good to run spec plugs for various reasons.

two things come to mind.
1. Vacuum leak. Check for a vacuum leak. looked for missing, broken and worn out vacuum lines running into the carb/s.

2. plugged up idle circuit in the carb. With the air cleaner/flame suppressor off of the carb/s, crank it, rev it to the top rpm's, then let go of the throttle linkage (simulating idle position) and smother the carb with your hand. doing that several times in a row often can clear a carb idle circuit.

 

[boobie]

Re: 1975 evinrude 40 hp 40555c

If you rev it to top rpm's it better not be in neutral or you might get a surprise.