30 HP Evinrude Question

I have recently been having trouble with my Evintude. It is a 1998 on a Lund S16 and the trouble when i hit my cruising speed, 18-20 MPH, it makes the sound like the hub is spun and drops RPMs. It started with the stainless steel prop which had dings and such in. I took that off and put on a brand new aluminum prop, it still make the noise and drop in RPMs. But then I ran the prop more, changing speeds and taking several hole shots, and it quit. Any ideas?

A spun hub will be corrected by a new prop. Generally with a spun hub, the RPMs will go UP, not down, based on less resistance.

This sounds more like a fuel delivery issue to me. Either failing fuel pump or a dirty carb. I say this based on the fact that it died. If it was only the ‘spun hub’ symptoms, I would start thinking about the lower unit.

Of course, it could be any number of things. Can you take it to a marine repair shop?

I’m not sure what you mean by “it makes the sound like the hub is spun and drops RPMs”. As DF pointed out, a spun hub causes the rpms to increase, not decrease.

If it’s bogging down, it’s almost certainly a fuel flow issue.

1. Do you have a fuel filter either on the outboard itself or an inline filter? If yes, replace filter to verify it isn’t plugged and/or restricting flow.

2. Verify your fuel hose doesn’t have air leaks. The easiest way to do this is to borrow a different hose and try it. You can visually inspect the hose, but this is not always accurate as a small pinhole leak can let in enough air to limit fuel pressure without causing a very noticable fuel leak.

3. You could have a clogged or partially blocked “high flow” circuit in the carb. Do you know how to remove and do a deep-clean/decarb job on a carb? If yes, do so.

4. Your carb could require a carb kit because of a leaking seal or o-ring. Personally, if I’m going to go through the trouble of a teardown per step 3, I almost always just install the kit.

Grouse

Jeez, I didn’t even think of the fuel hose! That’s a really good point, especially if you have an aftermarket primer bulb like an Atwood or something. Some people use them for years, others fail really quickly.

Just sort of a process of elimination here to chase it down. I would start with everything external that you can, basically do what TFG says in that order.

Keep us posted!

Also, make sure you’re gas tank is properly vented. The vent screw on top of the fuel cap should be turned counter-clockwise while running the motor.

I checked the fuel line, my fuel tank doesn’t have the vent (it is and old metal OMC), and I wouldn’t guess the carb because as you add more weight in the boat the RPMs should drop also with a lower top end. My dad and I went out this night and it was fine. My dad thinks that the motor has to be lowered on the transom.

Well, to be fair, you left out a lot of info. Is this boat new to you? Have you looked to see where the cav plate is in relation to the bottom of the boat? In any case, the motor shouldn’t die due to weight or transom height unless it was so starved for cooling water that it over heated. In that case, you probably have bigger problems.

Then again, if the problem has fixed itself…

The stainless prop when undamaged probably has more cup built into it. This helps prevent blowout by grabbing the water better. If damaged this can cause erratic behavior. An aluminum prop usually does’nt have as much, if any cup built into them. The drop in rpms when this happens could be a rev limmiter kicking in protecting the motor from over speed…just a guess. At near full speed you should see the anti cav plate just skimming the water surface, if it’s buried in the water it creates drag, if too high you can get blow out. Is your trim fixed of adjustable? If this is a new problem on an all ready existing setup I would guess its the damages stainless prop. I would check on getting it repaired.