Evinrude 1980s Fuel Pump Differences

[Steve Fournier]

I rebuilt a 1983 Evinrude 35 hp motor from the ground up meticulously.
The engine runs great except at WOT at 4500-4800 RPM when it starts to starve for gas and surges.
Squeezing the fuel bulb during that episode eliminates the surging.
After some research, I noticed some fuel pumps have a single vacuum connection and another for that time period has two vacuum connections. So, my question is did Evinrude make a change during the early 80s to correct a fuel delivery problem with the pumps?

 

[racerone]

Facts-----Just for you.----Those pumps are very good and reliable.--------Fuel pumps operate with a PRESSURE pulse and not so much with vacuum.---Some pumps mounted directly over the pulse port and just needed a fuel in and a fuel out connection.----Others such as the 70 HP did not mount on a pulse port and needed 3 nipples.----Pressure pulse , fuel in and fuel out.----I would inspect your fuel pump or perhaps test run with another tank and hose.

 

[F_R]

Steve, I thought this was hashed out on the other forum where you asked. Anyhow, without repeating what racerone said, your motor gets it's pulses directly from the bypass cover, where it is mounted. That system worked very well for eons on many models and no need to consider the other kind that uses a pulse hose. In fact, if one had to choose a "better" system, I would pick the direct mount, like you already have, if for no other reason than simplicity.

 

[racerone]

The other option is to install the fuel pump off a 1965 V-4 75 HP or off a 1966 V-4 100 HP on your 35 HP.-----They were capable of pumping plenty of fuel.