Pontoon Boat & Deck Boat Forum

Well, I hoped my issues with my motor were just fuel related - clogged fuel filter (it runs fine under 2000 RPM, but anything over that and it misfires). But after taking the boat out of the water on Saturday and pulling the filter, it looks fine. Checked the diaphram in the fuel pump and it looked fine too. I had 4 new plugs so I put them in -- noticed plug #4 had a little oil on it so I thought maybe it had fouled. After putting the 4 plugs in and putting the fuel filter back on, we dropped the boat back in the water. It ran great for about 10 minutes at high RPM (5500) but then I felt it misfire once and pretty soon it started misfiring a lot and losing power again. But when I back off to about 2000 RPM, it runs fine.

Any suggestions?? I will probably have to pull it out and check that #4 plug again to see if fouled again. Not sure what would be making it foul. Never had this problem before in the 3years we've had this boat till a couple of months ago was the first time we ran into this problem. Our lake had been too high to get the boat off the lift at the dock and get it on the trailer till this past weekend.

sounds fuel related, maybe you have H2O in fuel.
drain tank, change filters maybe borrow someone's portable 6 gallon tank to test before going thru trouble to drain tank

Good luck, boat troubles suck

Is your fuel tank properly vented?

I know when I had my little Honda, it helped to have the vent on the tank open or it would shut down like you're describing.

I also have noted that my Toon has a "Vent" near the filler cap.

If a mud dauber for example built a nest on your fuel tank vent, it could create a problem like you're describing.

Another thing to check would be fuel line, fuel bulb.

Would work fine at lower rpm's and could cause your issue.

Our fuel tank is built in -- actually, it's under a platform area where a seat is located on the port side. I'll check the vent near the filler cap to make sure a mud dauber has not built a nest in there. I'll also check the vent in the storage area where the tank is located since it vents to the rear of the boat. I know we do have a lot of mud dauber issues so I have to keep the cover for the motor on when we have the boat stored on the lift.

Would the vent cause the issues where it ran fine at high RPM for the first 10 minutes and then would start cutting out, but would fine at low RPM?

I'm going to borrow a buddy's portable 6-gal tank and bypass my normal fuel tank. I'll also use a different fuel hose (to eliminate any possible issues with my hose). If that runs fine then I'll start looking at the fuel hose on my boat. Since this is a 2003 model, it may just be getting old and possible cracks in the hose allowing air in the line.

Thanks for the suggestions. I'll report back after I've had time to check a few things.

With the plugs pulled checking the compression, do the muffs need to be on or motor in water? Or will it not hurt the impeller if it actually doesn't start?

If # 4 looks fouled again, could be the injector?

If you emptied out the fuel filter and then ten minutes later had the same issue....sounds like H20 in the water. Had a similar problem last year. Empty as much gas out of the tank as you can and keep changing the fuel filter. Add Heat and more gas. I think I went through 4 filters before I finally got the water out to where it was running smooth.

Does your Yamaha have a separate external 10 micron fuel filter besides the fuel filter/water separator on the motor?

Unfortunately, no there is no separate external fuel filter. We just have the standard small filter under the cowling. Since it's a 2003 (I think 2004 had the same setup), the fuel filter is not a disposable cartridge. It's a hard plastic with screen that you just have to clean in solvent, dry and reinstall.

We are pulling the carb off Thursday and going to check on a clogged jet. I guess I'll also be emptying out as much fuel as I can -- unfortunately, it's a 20 gallon tank and it's FULL. I'll also add some Heat to help with any H2O that main remain in the tank.

Thanks again for the suggestions. I'll report back after this weekend.

Turns out I have 4 carbs that all have to be in sync so we decided not to go with removing the carbs. We did remove all of the fuel from the tank, removed the tank completely and checked the tube inside the tank to make sure the screen on the end was not clogged -- all looked good. We used the air compressor to check the fuel lines for any clogs and they were good as well - refilled with new non-ethanol fuel. Checked the spark plugs and all looked fine. We tested the spark on each plug wire and they had no problems jumping the spark across the 11mm spec from the service manual. Launched the boat and again it ran fine at 2000 RPM but as soon as I got up to about 4000 RPM, the motor started cutting out really bad and losing RPMs. Dropped back down to 2000 RPM and it ran fine. Finally gave up and loaded the boat up to take to a mechanic. His first thought is the motor is going into "limp home mode". But he won't be able to look at it for a couple of weeks to determine why it is doing that. No alarms are going off, so not sure why the motor would be going into that mode.

So it looks our week-long vacation next week is going to be boatless. We'll just be floating around the dock for the week

OK Toon,
Just for grins and giggles........

Double check your battery connections, including the ground.

Make sure your battery is fully charged and is operating at the proper voltage.

The reason for this is a S.W.A.G. (Scientific Wild Assed Guess)

I once had a vehicle that had electronic ignition and an electric fuel pump.

If the battery cables were dirty or the battery not up to snuff, the engine would idle fine but wouldn't pull a load.

At one point, the battery was fine, but the ground cable had an issue.

We replaced the ground cable and never had the problem again.

So since you're week is screwed anyway, cleaning the battery cables and ensuring the battery is functioning correctly may just be the fix.


And for a bit of humor.............

A young guy from Texas moves to California and goes to one of those big "everything under one roof" stores looking for a job.
The manager asked, "Do you have any sales experience?"

The kid said, "Sure, I was a salesman back home in Texas."

The boss liked the kid so he gave him the job. "You start tomorrow. I'll come down after we close and see how you did."

His first day on the job was rough but he got through it.

After the store was locked up, the boss came down to see how things went.

"How many sales did you make today?"

The young man replied without hesitating, "One."

The boss said, "Just one? Our sales people average 20 or 30 sales a day.

How much was the sale for?"

The kid said, "$101,237.64."

The boss said, "$101,237.64?! What the hell did you sell?!"

the kid said, "First I sold him a small fish hook.

Then I sold him a medium fish hook.

Then I sold him a larger fish hook.

Then I sold him a new fishing rod.

Then I asked him where he was going fishing and he said down at the coast, so I told him he was gonna need a boat, so we went down to the boat department and I sold him that twin-engine Chris Craft.

Then he said he didn't think his Honda Civic would pull it, so I took him down to the automotive department and sold him that 4x4 Blazer."

Amazed, the boss said, "A guy came in here to buy a fish hook and you sold him a boat and a truck?"

"No sir, he came here to buy a box of tampons for his wife and I said, 'Well, your weekend's shot, you might as well go fishing.'"