mechanic can't diagnose????

[Mower]

I have a Larson w/ a mercruiser alpha1 generation 1 i/o recently I've been experiencing the following: Boat idles great has a fair amount of hesitation at mid throttle range ( almost bogs and then catches up) and then runs great up to full throttle. Here's what I'm noticing, not achieving max RPMs and have lost 6 or 7 mph on top end? Heres what I've done:new water seperator -even though old filter had no water in it, new plugs, new wires, new cap and rotor. along w/ routione fluid changes. I don't think this is an ethanol issue for it runs great at idle. I checked butterflys in the carb and she is fully open at full throttle? Compression is good through all 8 cylinders, only one cylinder is down 5 compared to the others. Any advise is appreciated.

[stevietangles]

it doesnt sound like an ignition problem but more a fuel delivery issue. rebuild the carb and see

[Big Dave]

Carb. The transfer from the Idle circut of the carb and full throttle isn't happening. Something is plugged ,or the power enrichment rod isn't working, Accelerater pump?

[borderline 350]

Dear Mower,

From your description........I would suspect that the accelerator pump in the carb. has insufficent volume. Test by looking very carefully down the primary venturis while someone else moves the throttle from closed to wide open quickly (ENGINE OFF!) you should see a steady full stream of fuel from the discharge port in each venturi. Do this test after the engine is warm and shut off!!! You may have to use a small flash light to see properly.

..............You could also have the primary rods sticking inside the carb. (that will cause a bog also and loss of fuel flow in midrange RPM.). THE BEST GUESS is to clean & rebuild the marine Q-Jet. USE someone who has done this kind of rebuild and has experience. I.E Hank @ Port Bay. Good luck with this nagging problem!

Sincerely,

Jet Boat Bill

[chowder]

Should be able to get a Jiffy kit for that carb, just check to see what's included-been a long time since I've gotten one (I'm surrounded by fuel injected diesels). If your gonna go up to Fairhaven, I'd let Hank at L&M have a look at it.

[Lew]

Hank L&M he's ur guy

[Big Dave]

My friends mercrusier 165 hp 6cyd had the springs in the distrubitor rust out. These were for the centrifical advance. That gave weird running conditions as the timing wouldn't stay put ,or work as it should. Got a rebuild kit at one of the autozone stores (mister gasket hod rod kit) that fixed us right up.

[beamer132]

hey

is your boat in a slip if so is yhe bottom painted?

[FISHSTALKER]

Sounds like water in the fuel to me.