can't throttle up under load

I just picked this boat up last season. It's 18'bowrider with GM inline 4, mercruiser alpha one outtdrive. Took it out a few times last year and i had to accelerate slowly to avoidbogging down and stalling. Now the problem has progressed to the point that it needs to be adressed. I took it to a mechanic, and I havent heard from him in 2 weeks, he hasn't returned any calls either. I think I'm going to go and get it back and fix it myself, where should I begin diagnosis. Fuel pump, filter, carb rebuild?

Re: can't throttle up under load

Start with the filter and work your way to the carb. I suspect it is an issue with the carb, but it is good to verify the others things along the way.

Re: can't throttle up under load

Before you start any of that, do some diagnoses... Throw a timing light on the engine and make sure the timing is advancing correctly.

You haven't given us ANYTHING to work with apart from "GM inline 4"... How about a year (of the engine, not the boat), or the serial number of the engine ... And is it a 120 or a 140? If it has points I would start with a full ignition system tune-up, including plugs, points, cap, rotor, condenser, and if they look remotely old, plug leads too (including the one for the coil to the dissy)... THEN start on the fuel system....

The problem may well be the carbie, but unless the ignition system is in good shape, you could have the best fuel system on the planet, and it'll still run like a dog....

Chris......

Re: can't throttle up under load

achris said:

I would start with a full ignition system tune-up, including plugs, points, cap, rotor, condenser, and if they look remotely old, plug leads too (including the one for the coil to the dissy)... THEN start on the fuel system....

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Couldn't agree more!

Since the OP seems to be finding out what many already know about how much fun marine mechanics are to deal with (personally they are a toss up with selling your soul to the damn devil!!) and I can understand why you would want to just do it yourself since it may actually get done before it starts snowing, and you wont have to mortgage your house to gain the privilege of waiting for ever without response only to find it most likely will still not be right.

Yea I am a fan lmao

Anyhow I really mean to stress that anyone wanting to be a boat repair DIY etc just take a few deep breaths and gain all the knowledge you can before just jumping in. I do not believe any of this is as hard or near the level of "specialty" that most everyone in the marine industry would lead us to believe, and with a little planning, some basic mechanical ability and knowledge, patience, some effort, and a willingness to do it right that anyone can take on over 80% of the maint and general repair most boats need.

One word of caution as it seems to come up often when someone with auto or home mechanic experience first tackles their boat (myself included lol) is not to assume that normal auto parts are just fine for your boat, and take the time to learn where you can cross parts, and where you could blow up either your boat, or your engine when trying to avoid the overly high mark up on marine parts we often see.

That all said I have found that 90% or more times my boat(s) have run poorly it has been due to either fuel supply, or spark (meaning anything from the ignition right on down to the plugs and everything in between).

Only once so far as it been anything major, and most times it ended up being parts that you would change during a major tune up (which you should do with any boat that is new to you, and not brand new etc).

Good luck, and let us know the outcome!