odd, and no idea where to start

[burninman]

2nd trip in my new to me monterey 4.3 mercruiser alpha 1. i had previously noticed the idle set extremely high on the 1st trip. i adjusted it down to ~700 rpm, it seemed to run fine. it also maintained that idle speed after a couple trips around the cove and dropping back to neutral. So i opened her up. for an hour. thing of beauty, planes in no time, gps said i was going 48-50 mph, not a single hiccup. went back to dock, installed a stereo, made some sock lines, anchor lines, etc, probably an hour, then took it back out.This time, different story. it ran fine for ~20 minutes, around 4000 rpm. then it just starts slowing down. no tugging, no pulling back up to 4000rpm, just a steady decline down to about 2000. throttling down and up again produced a wheezing sound from the engine, and a strong gasoline smell, pretty sure it was flooding, or not getting enough air. where should i start looking for what happened? the running great part first has me baffled.

 

[Don S]

Re: odd, and no idea where to start

It may need the throttle cable adjusted to preload the carb linkage to idle. It would help if you gave us some clue as to the age of this 4.3. is it a 1985 or a 2011 model? carbed or efi, what drive, etc.

 

[burninman]

Re: odd, and no idea where to start

it's a 2004 motor, in a 1995 boat, no idea about the carb, throttle assembly, any other accessories. i would think everything was at least examined when the motor was replaced, but i dont know what might have been replaced vs just screwed back on. i do know the ppl i bought it from did all that in 2008, and kept it till last year, so i believe it would have been done in order to use rather than to just sell.

 

[Don S]

Re: odd, and no idea where to start

it's a 2004 motor, in a 1995 boat, no idea about the carb, throttle assembly, any other accessories.

If you can't tell us what you have, it's going to be impossible to tell you how to fix it.

so i believe it would have been done in order to use rather than to just sell.

I wouldn't assume that at all.

Do you plan on doing the work on this boat yourself, or having it done?

 

[burninman]

Re: odd, and no idea where to start

If you can't tell us what you have, it's going to be impossible to tell you how to fix it.


I wouldn't assume that at all.

Do you plan on doing the work on this boat yourself, or having it done?

Depends what i can learn about the components involved i suppose. I'm not afraid of a car engine, but i've never worked on a boat motor before. I suppose I'll try the simple things i can figure out first; fuel filter, throttle assembly. How long does one of the water separating fuel filters typically last?
I feel certain whatever happened involves the fuel system, and there's only so pieces of that, right? I ran about half a tank out of it before anything went wrong. Also, when i initially adjusted the idle screw on the 1st trip, the throttle wanted to stick at it's old position when coming down from speed to idle. i cleaned all that out with some starting fluid and degreaser and it stopped sticking, so i assumed it was just dirty and used to where it was set. it was suggested then that the throttle cable might be bad, but like i said i could hear it trying to work, just sucking too much gas or not enough air.