I'm back! So a month or so ago, I posted about my Merc 4.3 4barrel acting up. I decided not to try and resurrect that thread. My 4.3 ran fine when I winterized it last year. This year, not so much. It starts in the driveway and idles great...upon getting it on the water, I hammer it and get up on plane. I can run at WOT, or near it. After a few minutes, it starts to fall flat on its face. specifically, it bogs, catches up, bogs. It will do this until it has dropped down to around 2500 RPMs, then it settles down and runs OK. When it first did this (again, about a month ago) I checked (on the water) that the choke was opening up, and it was. all 4 barrels were also opening up. I took it home and posted on here. Many suggestions were to check the fuel filters. I checked the fuel/water separator and the filter by the carb, right where the fuel line connects. That filter was very dirty, but not completely blocked. I cleaned, and took it back to the lake. Boat ran OK for a few minutes again, but the symptom came right back. At this point, I took it to a shop, where they replaced my Ignition control module...said it was weak.
I had assumed things were good, and that they tested it on the water, as i had specifically told them that this only happens under load, not on muffs. Last weekend, we took her out and the same thing happened. 466 dollars later, a clean filter, and a new ICM, the symptom remained.
Today, my boy and I tore apart the whole fuel supply system, from tank to carb. Everything was beautiful and clean. I even ran to the shop and we replaced the ignition sensor under the distributor, as I had one go bad in my old boat and had the same symptoms.
This is why I try to avoid shops. You pay big time and can't return stuff that doesn't help. There is only one close, and I got burned this time. I am thinking about taking it to another shop thats about an hour away (large dealer...good reputation), but wanted opinions first. I think its the fuel pump not keeping up. I could go buy a vacuum gauge and all the tools to diagnose, but with that cost involved I'd much rather spend my time other ways and let a shop do it.
My theory is that the bowl in the carb is full while we idle out to open water. Once we get moving, the boat runs OK until the bowl starts to get low, as the pump can't keep up with the volume. at 120 dollars, I don't necessarily want to just go buy one to try unless some other knowledgable (more knowledagble probably) folks agree with my theory.
Rob
I had assumed things were good, and that they tested it on the water, as i had specifically told them that this only happens under load, not on muffs. Last weekend, we took her out and the same thing happened. 466 dollars later, a clean filter, and a new ICM, the symptom remained.
Today, my boy and I tore apart the whole fuel supply system, from tank to carb. Everything was beautiful and clean. I even ran to the shop and we replaced the ignition sensor under the distributor, as I had one go bad in my old boat and had the same symptoms.
This is why I try to avoid shops. You pay big time and can't return stuff that doesn't help. There is only one close, and I got burned this time. I am thinking about taking it to another shop thats about an hour away (large dealer...good reputation), but wanted opinions first. I think its the fuel pump not keeping up. I could go buy a vacuum gauge and all the tools to diagnose, but with that cost involved I'd much rather spend my time other ways and let a shop do it.
My theory is that the bowl in the carb is full while we idle out to open water. Once we get moving, the boat runs OK until the bowl starts to get low, as the pump can't keep up with the volume. at 120 dollars, I don't necessarily want to just go buy one to try unless some other knowledgable (more knowledagble probably) folks agree with my theory.
Rob
