Thoughts on my outboard issue

MIKE-SID

MIKE-SID

Active member

I had an issue on the last day of early season. I thought I'd see what you guys think while I'm waiting for the carb parts I think will solve the issue.

I ran the boat out to my spot in the dark as usual, mostly 1/2 throttle and a bit full. No problems. As I was hunting, I realized the vent was closed on the tank. The tank was sucked in a bit. I opened the vent. When I came in, the boat would not run full throttle without sputtering. I ran in 1/2 throttle and it ran ok. I ordered the diaphragm and gaskets, and reeds for the carb. Did I do damage running with the vent closed? It's not running really smooth at idle either.

I'm thinking I stretched out the diaphragm? I took the carb apart and cleaned it, no change. Turns out when I paid for 2 day delivery for the parts, that meant 2 days after they get them in stock. [frown]

Mike
 
What engine are you running? Does it have a fuel pump in addition to the diaphragm in the carb?

I doubt the diaphragm was damaged. If it had been, the effects would have been more noticeable when under the greater load of the vent being closed, not when the vent was open.
If the tank was partially collapsed, it stands to reason that the fuel lines were also partially collapsed and under undue stress. This may have caused small pieces of debris to dislodge and be plugging something. If you are sure you got all debris out of the carb, have you checked the line itself? You may have a blockage where the line attaches to the tank or where the line attaches to the motor (assuming there are quick disconnects at these points). These fittings will create a "pinch point" in the fuel flow and are suspect for clogging (as well as the small passages in the carb).
 
Could be a range of issues, air leak in the bulb/fuel line, clogged filter or a clogged high-speed jet. Never heard of a diaphragm stretching.
BTW, I cover my tank's cap so rain doesn't get in and keep the vent open at all times.
What brand & size motor?
My 25 Merc has a filter under the cowl in addition to the one in the tank.

If its any consolation, it's not running at all. Sat for 3 months without running, appears the gas went bad even though I use Stabil. Its gas from the end of last duck season so I shoulda expected that.
Plus the plugs were horrible shape, probably the original plugs (2003). Flooded it when I tried to start it.
I've replaced the plugs, drained/cleaned the tank, lines & filters, just haven't had time to take it down to the gas station.
There are lots of gas stations here with non-ethanol, I'm sticking to that from here on out.
I've got another month before our season starts so I have time!
 
When dealing with carb, fuel related issues I always start with a fresh tank, fuel, bulb and line. Don't run off your regular tank. Not unless you can completely drain it and let it dry. I use an air compressor and blow out all the jets and orifices when I finish soaking my carbs in cleaner, it doesn't take much to booger one up.

Do you run an inline fuel water separator and ethanol free fuel? So many of our issues with outboards are caused by Ethanol is why I ask. I've cut fuel line open and seen the affects of ethanol inside the liner of the fuel line. That stuff is bad news for sure.
 
P Taylor said:
When dealing with carb, fuel related issues I always start with a fresh tank, fuel, bulb and line. Don't run off your regular tank. Not unless you can completely drain it and let it dry. I use an air compressor and blow out all the jets and orifices when I finish soaking my carbs in cleaner, it doesn't take much to booger one up.

Do you run an inline fuel water separator and ethanol free fuel? So many of our issues with outboards are caused by Ethanol is why I ask. I've cut fuel line open and seen the affects of ethanol inside the liner of the fuel line. That stuff is bad news for sure.
Click to expand...

No Ethanol fuel is not available in CT. The gas was days old, and when I put in the mix, I use marine stabilizer to treat it. Nonetheless, I'll use fresh gas from a clean tank.
I ordered a new line connector to the tank side that looks suspicious.
 
ethanol fuel has been known to weaken inner fuel line liner to point of collapse on older tanks. Newer fuel lines they,ve overcome those issues except for the wally world lines. When replaceing get some good marine fuel line rated for ethanol fuel delivery. The collapse from those older lines will stop fuel flow under load but may not yet be the point of deteriation that would show up in filters. Although I treat my fuel with blue stabil at storage rate I,ll still pump it out and into vehicle after a couple months of no use. The mercury marine step 1 fuel treatment works wonders also with ethanol fuel. I run that in my 90 etec and 25 tohatzu,. The blue stabil I,ve used since its introduction in my merc 8 & 15 2 strokes and in all my mowers ,saws, leaf blowers etc. No issues even on chain saw setting in tank for many months.
 
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A lot of good suggestions but I am going with a fuel pump. You can damage the fuel pumps if the motor is pulling a heavy vacuum against a closed vent.
 
I moved my gas tank to the bow years ago and had gas problems. Bought West marine fuel line and it had a liner problem. Cut it back at both ends and solved the problem.
 
Jay K said:
A lot of good suggestions but I am going with a fuel pump. You can damage the fuel pumps if the motor is pulling a heavy vacuum against a closed vent.
Click to expand...

I don't think my 15 hp has a fuel pump per say
 
Capt Rich Geminski said:
I moved my gas tank to the bow years ago and had gas problems. Bought West marine fuel line and it had a liner problem. Cut it back at both ends and solved the problem.
Click to expand...

I cut both ends, and ordered a new connector. because one had a cracked gasket/grommet.
All my parts are coming tomorrow so I'll be ready for a test ride Saturday or Sunday.

If there is still a problem, I'll have to look toward electrical, like coil, but I don't think that will be necessary.
I appreciate all your ideas.
Mike
 
I have an old and somewhat cranky 25 mariner on my boat. I have taken to purchasing a new fuel line at the beginning of every season now and that has solved a lot of my fuel related issues.
 
Mike-
If all else fails there is a Yamaha dealer in Stamford or Greenwich -Catalano's- maybe you could pick there
brain on what might be causing this.
 
Chris H said:
Mike-
If all else fails there is a Yamaha dealer in Stamford or Greenwich -Catalano's- maybe you could pick there
brain on what might be causing this.
Click to expand...
I just remembered, two members of one of my gun clubs, race boats with small outboard motors, they are experts. I will seek their advice if my efforts fail tomorrow.

Thank you for the tip!
 
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Josh Schwenger said:
Fuel pump diaphragm IMHO. Pump the primer ball see if it runs better I've had to run home pumping the ball in my hand.
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Pumping the ball did nothing, but I ordered the diaphragms and other #
" fuel pump" parts.

After looking at the exploded view of the carb in the shop manual, I never removed the cap, and blew out the pilot jet either.
Thanks, Mike
 
Some fella from down here in SC mentioned using a compressor to blow out the jets / orifices. [;)]

I have stripped a bread tie wire or something similar to push through each and every orifice in a carb while cleaning it too. Hope you get her squared away, there's ducks that need hunting!
 
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