Ran my boat for the first time this year. Cranked it at the house on a hose before I left to make sure all was in order and it ran fine. Got to the river and the gas station I buy non ethanol gas from was closed. I had a tank with old gas- at least one year old, possibly 2, so I took a chance and used it. Boat ran fine for a few minutes then started surging and losing power. Restarted and ran fine for a mile or 2 and did the same and quit running. It did this several times and finally got to the point that it would not start at all. Towed it back and went home. Removed both carbs and they were very clean and the jets were clean also. I had rebuilt both carbs last year and had only run it a few times so I expected them to be clean. I was assuming it was just water in the gas but the more I think about it may be something else. I remember that while running fast it started making a sucking sound and several seconds later it would stall out and die. It did this 2 or 3 times. Then it just got harder to start and it would die as soon as I applied gas. Now I'm wondering about an air leak, I've never had that isssue before. Would that make it not start at all? Also wondered about the fuel pump. I planned on cleaning the fuel tank and lines, and seeing if the fuel pump pushed gas thru the lines when I turn over motor. Then reinstall the carbs and see what happens. Not sure how to find a possible air leak. For what's it worth, the sucking sound came from the motor, not the line from the tank to the motor. Also, the bulb was firm and not collapsed or soft. I plan on doing a compression check and spark test this weekend. Just seems like a fuel issue but I'm not sure.

Any thoughts would be appreciated. Thanks

I've had that happen with my Evinrude 90 and my Merc 9.9 both times it was a pin hole in the fuel line.

It sounds like a fuel line problem to me also.

Dan

If you think it's a fuel issue and the carbs are clean I would check fuel pump and gas lines. They break down over the years and can start flaking off plugging stuff up.

Did you remember to vent the tank? Don't ask how I know to ask this question!

Sounds like bad gas to me. I’d start by dumping the old gas and replacing with fresh. Nothing good comes from old gas, especially if it had alcohol in it.

It could be this simple!!

I'm thinking bad gas and or plugged filter. That is if you already checked what NH114 said.lol

Finster, was the pin hole between the tank and fuel pump? Would I be correct in assuming that if it was between the fuel pump and carbs it would not suck in air, rather be pushing fuel out? I'll look closely for a leak.

The tank has one of the built in vents in the cap. I had a vent issue on another tank but it caused the bulb to collapse, would that normally be the case because the bulb and line seemed fine. I will also be trying another tank and line. I'm also going to make sure the connection at the cowling is good. I replaced the fuel lines last year when I rebuilt the carbs.

Is turning over the motor to see if the fuel pump is sending gas to the carbs the best way to test it?

Thanks for all the replies.

If it is not what was already suggested then join us at www.iBoats.com where there are thousands of mechanics and tens of thousands of owners to give input. I found parts for a 1941 Johnson and a 1958 Evinrude there as well

Thanks traprjohn!

Cracked coils can give you a fit as well on those older ones.

Yes, between the tank and the fuel pump. Both times. The odd part is that my primer bulbs would still pump up and not spill enough gas to notice but it would suck plenty of air. Another thing could be the little rubber o-ring on your connector if it has one.

Ended up having a small crack in the fuel line between the filter and carbs. Apparently when the motor was turned a certain way it opened the crack and it would suck air. $1 worth of fuel line and it cranked right up. Thanks for all the replies.

Yup, had it happen, it will drive you bats.

I had a 15HP evinrude that would run fine with the hood off, but only about half throttle with the hood on. Come to find out it was a gasket on the exhaust side of the motor. It couldn't, get enough O2 with the hood on to burn the fuel. They can be frustrating at times.

Used too much when it was new.
Small engines dont like old gas.

Fuel line issue. Make sure the gas tank vent is open too.