1971 40hp evinrude

[cschmid44]

I've go a 1971 40hp ski-twin outboard. I've used it several time this year with no problems. Just recently i took it out and it started up fine. But, when i pushed the throttle forward it barely moved. it cruised fine but at a very slow pace. What could the possible problem be? Anything will help. Thanks

[boats.net]

Need some more information. Will it not rev up, does it idle, are there any other symptoms?

[cschmid44]

It idles just fine. Yes, it revs up and will start going but very slowly. There havent been any other symptoms that I know of.

[boats.net]

Would you say that it sounds like it is going fast, but not actually moving. If this is the case, I would say you are having propeller issues.

[cschmid44]

Yeah I guess I would say so. But, I just put a brand new propeller on it. What else do you think it could be?

[boats.net]

Did the problem start after the new propeller? I am uncertain what else it could be.

[cschmid44]

Yes it did. I've had the new propeller on it for a few months with no problems until recently. What do you suggest I do? Thanks for your help.

[boats.net]

I am uncertain, if new propeller worked good for a while and it checked out good after problem started. The only other thing I can think of is lower unit, motor runs good right?

[cschmid44]

Yeah, the motor runs great. Should i change the oil in the lower unit?

[boats.net]

Scribe a line across prop hub and prop shaft, run boat and recheck line, if still lined up prop hub ok, otherwise prop hub is slipping.

[cschmid44]

Alright,did the scribe and everything checked out good. I dont know what else to do. Any other suggestions?

[boats.net]

Do you have access to a tachometer? If so hook it up to your boat and when running wide open throttle note the rpm's. This will tell us if you are getting full rpm out of your motor. If you are getting full rpm, then the problem is either your boat has excessive drag or there is a problem in your lower unit.