Johnson - Evinrude 75 HP fuel problem

Larry71

Recruit
Joined
Aug 24, 2012
Messages
2
Hello All,
this is my first post so I hope I can make sense with my problem description.
My 1980 75 HP Evinrude totally bogs out on acceleration - unless I run the fuel line directly to the fuel pump (without the primer bulb or water separator).

this has been going on for a while and it's been in the shop several times for the same symptom. It runs fine for one or 2 times out afterwards, then goes back to the bog and only goes 5 mph max. It seems like the shop doesn't really do anything - it just runs ok for a while is my guess but I'm totally frustrated and out almost $1,000 to them so far.

I always use fresh fuel and add Starbrite treatment in a 6 gallon portable tank and I added a gas/water separator too.
After this last trip, I thought I had it figured out. I was out and it started bogging bad again. I bypassed the primer bulb and gas/water separator and it ran fine. WOT was great and idle seemed even smoother.

I bought a new primer bulb and new filter for the separator. It ran ok for a few minutes, then same thing. I bypassed them again and it ran ok. The clamp fittings and hose are new.
I'm thinking fuel pump?

any suggestions would be appreciated.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Johnson - Evinrude 75 HP fuel problem

Sounds like you still have a problem in the boat fuel system and not the fuel pump. Otherwise it wouldn't run good when you by-pass it.
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Johnson - Evinrude 75 HP fuel problem

You can constantly pump the primer bulb and it will bypass the fuel, if it runs properly doing this you need to replace/repair the fuel pump.
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Johnson - Evinrude 75 HP fuel problem

I think he said he took the primer bulb out of the system and it ran good.
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Johnson - Evinrude 75 HP fuel problem

He did, but he was questioning the fuel pump. Just trying to offer a way of bypassing the fuel pump to eliminate it without costing anything.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Johnson - Evinrude 75 HP fuel problem

Daviet, read his first post.
 

Larry71

Recruit
Joined
Aug 24, 2012
Messages
2
Re: Johnson - Evinrude 75 HP fuel problem

thanks everyone for the replies and suggestions.
someone else also said it doesn't sound like the fuel pump - that's what got me to try posting to the forums.

I'm stumped about what else it could be.
I had the carbs rebuilt at the beginning of the season.

I can only think of a few possibilities

1. could it be a "weak" fuel pump?
2. can I try the pumping the bulb test with ear muffs on?
3. what else is left to check/change on the fuel system?

thanks again,
Larry

I just thought of this and wanted to add.

It looks like the previous owner used 3/8 fuel line and fittings etc.
The bulb and gas/water separator are 3/8.
when I looked up the motor, it says 5/16th line.

could that be creating this mess?
 
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