What is wrong with my outboard engine? 1977 Evinrude 25HP?

Question

The motor starts right up then at full throttle it runs fine for about 200 yards then it slowly goes down to an idle on its own and you let up and go full throttle again its fine for another 200 yards but it only does this after riding for about 15 minutes. what could be causing this. also their is a small leak on the lower unit on the rounded part near the prop shaft where four screws go in is there a gasket that goes in there or do i need to just silicone the screws in.

Answer 1

sounds like a weak fuel pump. I had a Johnson 25 that did the same thing.

first check to make sure the vaccum line to the fuel pump is not cracked.

FYI - johnsons and evinrudes of that era were virtually identical. both made by OMC

Answer 2

My Evenrude did this very same thing it was the fuel pump. For the leak there is a seal around the shaft just remove the prop and the 3 bolt's and seal replace and add oil back in the lower unit good luck

Answer 3

Sounds like the fuel pump or a fuel restriction from line, filter, bulb,,see if the bulb is going flat,,

Answer 4

Silicone isn't stupid, but don't use it on an outboard.  Get the right part and fix it right.  Your parts catalogue and engine schematics are available online at www.shop.evinrude.com

If oil is getting out, water is getting in.  you'll want to get that fixed and change the gear oil.

I agree with the previous poster about the fuel pump.  Might want to check the tank for debris first, and see if the fuel fittings are sucking air (listen close at the fittings while pumping up the primer bulb).

Maintenance on this engine is well within the scope of the average do-it-yourselfer with some basic tools & a good service manual.

I highly recommend the factory service manual, look for it at http://www.kencook.com or http://iboats.com

Answer 5

no dont silicone it in thats stupid....