[lsauls]

Guys, I am at the end of my rope. I have gone out 3 times this year (always on short sea trial runs with not much expectation of fishing), only to have to return to the slip/channel after clearing the jetties due to hesitation in one of my engines. I have completed everything that I know of (maint. wise) to solve the issue but since I can not figure it out, was hoping some of the folks on the board might have some advice.

Here goes...

Engine is a 200HP Mercury Carb. OB, 1998 model with just under 300 hours. I know that this alone (the engine make, etc...I am just a Yamaha guy but could not pass on the deal on this particular boat) is likely the first thing to consider but in this particular case, I can not justify a re-power (Fuel, Fed. Reg's, etc.).

Both engines idle exceptionally well, STBD engine hits 3000 ROM and either completely shuts down or slows back to 1500 or even 2000. Starts right up and runs (idles) great as long as I do not get to or above 3000.

- 3/4 of the fuel is 100% fresh with fuel treatments to reduce water, sludge, etc.
- New Water/Fuel Sep. filter installed.
- New fuel filter installed inside the engine.
- Rebuilt fuel pump.
- New pick up tube in tank.
- New Anti siphon Valve.
- New fuel hoses, primer bulb, etc.
- When the primer bulb is pumped, engine runs great at all RPM ranges so I do not believe the issue is relating to carb. or electrical devices (Plugs, trigger, coils, power packs, etc.). Plenty of power and immediate pickup.

Basically, once the fuel in the bowl is burned, the engine loses it's ability to feed the proper amount of fuel to maintain any RPM's above 3000.

No alarms and no common set point really for RPM (RPM needle bounces big time)...does not give me the impression that it is the engine trying to go into some type of conservation mode.

Please help! Any opinions or advice is greatly appreciated. I am thinking of just buying a new fuel pump just to make sure the rebuild did not totally address the problem.

[CharlieB]

You already described the solution.

When you pump the primer bulb it runs fine at all speeds because YOU ARE THE FUEL PUMP.

The fuel pump is failing to flow enough fuel for the engine to perform more than 3000 under load.

[This_lil_fishy]

Re-rebuild your fuel pump, you missed something. Possible tore the gasket, or one of the vacuum hoses are cracked or something to that effect.


Ian

[lsauls]

Looks like a new fuel pump is in order...

Thanks!

[hkeiner]

The below thread contains a troubleshooting guide for fuel starvation situations. If can help you narrow down the problem between a failed fuel pump or a restriction in the fuel line between the fuel pump and the fuel tank.

http://forums.iboats.com/showthread....ight=fuel+pump

[BOTE3]

same problem check the fuel vent hose if you have inboard tank mine was clogged and when i blew it out motor runs fine now

[j_martin]

Pinhole leaks in the suction line could do this.

An aftermarket replacement bayonet connector (plastic) could do this.

A soft or leaky pulse hose, including a brand new tygon hose, between the crankcase and the fuel pump could do this.

A hose with a ruptured innertube in the fuel system could do this.

hope it helps
John

[CharlieB]

Ah, guys, did you notice that this thread is a YEAR OLD?