Man, am I glad I found this forum!

[Wannagofishin]

Does it always fail?  Or only when it gets hot?

I don't know that it gets hot - don't have a temp gauge. But I always let it idle a bit before leaving the ramp and then through a no-wake zone. Once out of the NWZ, I give it the gas and for a few moments it runs fine, then hesitates, like I said, like it's starving for gas. I ease back on the throttle and it runs OK - fairly smooth. The pee water is hot, but no so hot I can't hold my hand under it.

Dan

[jack1747]

ok, i would say that it is failing all the time.  Not just after its been run along time and is completely heated up.

Can u give us some idea of rpm's when it fails.  Like it runs 1/2 throttle all day long but fails at 3/4 throttle all the time.  Or it runs ok at just above idle while going thru the nwz but fails as soon as the throttle is above that.  Etc.  I am trying to figure out where in the power curve it is failing and does it always fail the same. 

[horsefly]

Maybe old fuel line caving in shutting off fuel flow at higher rpm??? Bad cylinder compression? Trash in water pump valley or line? Does it shut off? Oh speaking of fuel, maybe trash or water(moisture) in carbs/floats and needles?

[Wannagofishin]

Yeah, all the time. Not sure of the RPM's. The tach I have leaves a lot to be desired. It's at WOT. Cruises for a minute then almost dies - it might die if I didn't throttle back, not sure.

If I had the money, I'd hang a 50-60 HP on her. I run a heavy boat. Lots of tackle, rods, cooler, TM, two fishing seats, two tanks, two batteries, heavy deck and floor. Yup, I need more power!

Dan

[jack1747]

It's at WOT. Cruises for a minute then almost dies - it might die if I didn't throttle back, not sure.

Sounds like fuel to me.  Did you replace the primer bulb when you replaced the tank and lines?

[jack1747]

next time it fails try pumping the prime to see if it catches back up..

[jack1747]

was the gasline replaced AFTER the crabs were rebuilt?

[Wannagofishin]

Maybe old fuel line caving in shutting off fuel flow at higher rpm??? Bad cylinder compression? Trash in water pump valley or line? Does it shut off? Oh speaking of fuel, maybe trash or water(moisture) in carbs/floats and needles?

It's all new. (Tanks, bulb, and line from tank to carb) Plus, I have a water separating fuel filter and the carb I just rebuilt. I'm not a master mechanic, but I've been working on engines (four stroke) since I was a pup. I was sop foreman at a Triumph dealership, and I've built and rebuilt God only knows how many bikes. All four stroke - not too much experience with two strokes.

Dan

[Wannagofishin]

next time it fails try pumping the prime to see if it catches back up..

Did that. No difference. I watched the filter bowl on the engine while a buddy drove. No loss of fuel.

Dan

[horsefly]

was the gasline replaced AFTER the crabs were rebuilt?

Good point and stored over time with Stabil-gas or other too. Maybe and he has a water leak....in the hull so with the weight of the boat and gear and then the water, it bogs down? I still think it's fuel related if not a cylinder or two that is weak IMHO, but...............JACK, is the small engine pro on here

[horsefly]

Did that. No difference. I watched the filter bowl on the engine while a buddy drove. No loss of fuel.
Dan

How about bubbles???

[Wannagofishin]

was the gasline replaced AFTER the crabs were rebuilt?

Same time. I'm convinced it's not the fuel system.

Dan

[Wannagofishin]

How about bubbles???

No bubbles. I thought it might be a pin hole in the line somewhere, but no evidence of it. I've thought about replacing the whole line and bulb but don't have the money to waste on trial and error. I know the purge ball in the bulb can go bad but it pumps up and holds firm.

Dan

[jack1747]

It's all new. (Tanks, bulb, and line from tank to carb) Plus, I have a water separating fuel filter and the carb I just rebuilt. I'm not a master mechanic, but I've been working on engines (four stroke) since I was a pup. I was sop foreman at a Triumph dealership, and I've built and rebuilt God only knows how many bikes. All four stroke - not too much experience with two strokes.

Dan

Well then, as you know,  the resistance between the electrodes of the sparkplugs go to the highest because of more gas and oil particles in the cylinder during wot.  I gona take a swag here now.  In 2 cycle engines there is a thing called reserve voltage.  There is a special tester to test it.  If it takes lets say, 15000 volts to fire the plug at 1/2 throttle and 35000 volts at full throttle but the coil reserve voltage is only 30000 the cylinder will fail at wot.  more than likely you have a bad power pack/coil or low voltage to the same.....

[jack1747]

try gapping the plug to .060....  this might make the engine fail on muffs... then u will be able to id which cylinder it is

[Wannagofishin]

Can't gap my plugs. I did pull them yesterday and the top one was a little fouled (very little) and the bottom was clean as a whistle. Both wet.

This is a "it ran fine last time out but this time I have a problem" situation. It only sat for two weeks between outings, covered and only a fuel fill-up difference between runs. (BP gas) If I knew more people here, I'd borrow a known working tank and fuel line just to be sure it's not fuel. Otherwise I need to take it to a mechanic with the instruments to do the tests I can't.

Dan

[mreinke]

Well I guess I will have to get my boat running so we can go fishing. LOL
I just need a couple more things an we are off.
Mike

[Wannagofishin]

Well I guess I will have to get my boat running so we can go fishing. LOL
I just need a couple more things an we are off.
Mike

Sounds good to me, Mike. Someone's gotta show me how to catch a cotton-pickin Florida bass. 

Dan

[mreinke]

If you have a little time during the week. Go over to city center and fish the pond there.I was getting some small ones ( around 3 lbs. ) on plastic worms. I was told that they get them over 10lbs. there . but there cant be to many of them that size in there.
Mike

[jack1747]

Can't gap my plugs.

Huh?  Opening the gap to .060" will help simulate running at wot.  By opening the plug gap you might find that the engine will not even idle.  If the plugs fire ok with the gap open that wide, I doubt you have an ignition problem..

[Wannagofishin]

Huh?  Opening the gap to .060" will help simulate running at wot.  By opening the plug gap you might find that the engine will not even idle.  If the plugs fire ok with the gap open that wide, I doubt you have an ignition problem..

Mine don't have the ground electrode. Don't know the term for them but they are flat.

Dan

[Wannagofishin]

They're called surface discharge.

Dan

[jack1747]

OH.. Surface gap plugs.... You could get a set of standard plugs to help you diagnose your problem.. BTW, I have seen surface gap plugs cause all kinds of weird problems.  I am not a fan of surface gap plugs.

edit... First thing I would do if you brought the engine to me is put Merc's recommend plug in. 

[Wannagofishin]

edit... First thing I would do if you brought the engine to me is put Merc's recommend plug in. 

They are the plugs Merc recommends. Straight from Mercury Parts Express. NGK BUHW.

Dan

[R D]

Take some WD40 and spray down the coils and wires,the WD will make it fire right if there is a crack or moisture but those old Merc's had a lot of electrical failure under the flywheel.