1964 Evinrude 40 only moves boat at low RPM

[johng87]

Hey Guys,

Maybe someone here can help me out. I have a 1964 Evinrude 40 horse. Last time i was out in the fall the boat would propel nicely through the water at a low rpm, but as I gradually brought the revs up on the motor from idle, it would seem to lose grip somehow and the enigne would rev up but lose all propulsion.

Before I take the flywheel off what should I be looking for other than a sheared flywheel key? I'm not sure if that owuld give me these symptoms.

I checked the prop shear pin, and it was twisted some, enough to have to be replaced, but it was intact.

Note that the weeds in the lake were pretty high at the time i was out there, i know big mistake.

so any suggestions?

Thanks so much,

John

 

[wavrider]

Re: 1964 Evinrude 40 only moves boat at low RPM

If it starts and runs it is not your flywheel key

welcome to I-boats

I would check your prop, sounds lke you have spun it, where the rubber center piece attaches to the outer aluminum part, shear pin will still be in tact.

If it is your prop it wil move at low rpm but under load and at higher rpm it will just rev the engine and not propel forward

take a permanant marker mark the outer metal of your hub with a line going to the rubber center piece, basically draw a line across the back of your prop by the shear pin

take the boat for a spin, get it to rev up like you mentioned

bring it back take the boat out of the water and observe where your line is at,, if it is not as it was when you drawed it then your hub is spun, need to repair it or buy new prop

I have a 1970 33 hp, I replaced my 3 blade with a 4 blade prop, part number AMC444,,, made a world of difference on hole shot and lower end torque, I pull my son on the knee board no problem pushing a 16' runabout
those old twins are hard to beat.

 

[F_R]

Re: 1964 Evinrude 40 only moves boat at low RPM

Exactly. All evidence points to a spun propeller hub. An even easier way to mark it is to just draw a line doen the plastic nut and prop. If it spins, the shaft & nut will no longer be aligned with the prop.

Gotta ask this though: Is your motor electric shift? Could be the clutch slipping. You better hope it's the prop.

Also, a gob of weeds will make it cavitate and lose propulsion. That's an everyday event down here in the swamps. Only cure for that is get the weeds off or stay home.