[Juno]

Hi guys, I just bought a 1992 Mariah Diablo with a 3.0l Merc. I took it out for its maiden voyage last night and noticed the following.

Motor starts up and idles fine. It does shake a bit at first but when warm its all good. The motor does not diesel when shut off. And will start up fine after its warm and shut of and then fired up again.

Problem was when I went to give it the gas to gradually get it up and out of the hole the motor would hesitate. First few times I actually heard it sniff and back fire slightly. WOT runs great, it just occurs around 2500 rpm under load. In neutral reving it up is fine, nice and smooth.

Any ideas, i was going to pull the plugs and check them. Could the carb need cleaning? HELP.

Thanks,

[SEMIJim]

Does she do it when you accelerate normally or quickly? What happens if you accelerate very slowly? It could be a worn-out accelerator pump.

When you accelerate a carbureted engine, the air gets moving faster more quickly than the gasoline flow does. This would result in fuel starvation, perhaps enough to stall the engine, were it not for a little pump in the carburetor, called an "accelerator pump," that squirts a bit of extra gasoline into the carburetor's throat(s) as the accelerator is advanced.

They eventually wear out and must be rebuilt.

Btw: It's the accelerator pump you're using to "prime" the engine when you "pump the gas" on a carbureted engine to get it started.

Jim

[Juno]

When I accelerated quickly it had a brief hesitation but then pushed through it. Slowly was like a longer hesitation, and a small backfire. When i felt the hesitation mind you i pushed down on the throttle to give more gas. The rest of the acceleration seemed fine and responsive.

Is this a hard thing to replace/rebuild?

Thanks for your help.

Andrew

[Juno]

I had the carb kit done by a local marina. This has fixed the problem. The motor is running great now, thanks for your help.

[SEMIJim]

Glad you got it fixed, Juno. I apologize for missing your follow-up question. In answer to that: How hard it is depends on the complexity of the carburetor, your knowledge and your skills. If you have no experience with that kind of thing, it's probably best left to a professional--or at least somebody who has experience. Gasoline and boats is a hazardous mixture, and it's easy to foul-up a carb rebuild in such a manner that you end up with raw fuel all over creation. (Trust me: I've seen it happen.)

Jim