4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 rpms.

[Air Traffic]

I am relatively new to boating and last year purchased a 1989 Thompson Daytona 270 with twin 4.3 mercruisers/alpha ones. Boat has had very little use with only 350 hours on each engine. Before starting out last year I had the impellers changed, lower units serviced and put fuel/water separators on each engine since they didn't have ANY filters installed. Yesterday we went for about a 30 mile run in Lake Huron, the boat ran great the first 29 miles then after slowing down to look at something I accelerated to get back on plane and the port engine stalled at 3800rpm,s. Brought the boat back down, and it started up without issue only to do the same thing 3 more times. Limped back into the marina at low rpm's. Could it need a new filter already, probably only 30-40 hours on it? Also the filter is located on the bulkhead apparently lower than the tank, with the fuel pump lower yet on the engine. Will I need to pinch the fuel line to change this since it doesn't have a shut off valve? Any other thoughts? Like I said, I am relatively new to boating and could use some ideas.

 

[sptjet90Reflexx]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

this is almost exactly what happened to my 89 4.3L yesterday out on the water. It was the first time the boat saw water in probably 5 years minimal. She started up great and up to WOT and ran great, problems started after I went down to idle and then tried to go back to WOT. She would stall out.

My post everyone is saying check the fuel filter but as you describe it appears to be no filter right? solid metal line going from the carb to the pump?

Apparently the filter is tiny and is located in-between the large nut and fuel line on the CARB itself. Im going to be checking mine later today but i bet its pretty gunked up.

 

[Air Traffic]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

My boat has plastic lines between the pump and carb. Trying to recall if there appears to be a place a filter could be inside the connection. Boat is moored 100 miles from home so want to have all "my ducks in a row" when I go to work on it. Thanks

 

[Bondo]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

My boat has plastic lines between the pump and carb. Trying to recall if there appears to be a place a filter could be inside the connection. Boat is moored 100 miles from home so want to have all "my ducks in a row" when I go to work on it. Thanks

Ayuh,.... Welcome Aboard,.... Yer motors should have a fuel filter, inside the fuel pump, 'n another in the carb's inlet fittin',...

If ya haven't already, Now is the perfect time to add canister type filters, Before the fuel pumps,...

 

[Air Traffic]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

Do I need to take the fuel pump off to get at the filter?

 

[jonny rotten]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

Do I need to take the fuel pump off to get at the filter?[/QUOTE I HAVE NOT DONE THIS,SO CONFIRM.You don't need to take pump off,there is a screw at the end of pump,loosin it and take off filter.You relize there are many things that could be causing your problem,somehow I dought its JUST your filters.

 

[Air Traffic]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

Do I need to take the fuel pump off to get at the filter?[/QUOTE I HAVE NOT DONE THIS,SO CONFIRM.You don't need to take pump off,there is a screw at the end of pump,loosin it and take off filter.You relize there are many things that could be causing your problem,somehow I dought its JUST your filters.

I realize that others things could be causing the stall but have to start at some point. If you doubt it is filters what do you think it is?

 

[Eric 3.7LX Alpha 1]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

Filters should be routine maintenance yearly, and if your's haven't been done.... there's nothing wasted in new ones...

 

[jonny rotten]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

I had a similer problem.Idled fine,fine with muffs on.Under load it backfired and bogged.I changed the fuel pump and it fixed the problem.My filters were near perfect.Still have a slight carb issue,needs a rebuild this winter.Smell the dipsick,does it smell like unburnt gas?If so it could be a bad pump,Or anti siphon valve,carb,clogged gas line vent...

 

[NHGuy]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

Air Traffic, does only one motor act badly? Get 2 more water fuel separator canisters. Remove the ones currently in service and pour the fuel into glass jars. If there is water it will separate out in a short time, it will lay at the bottom below the gas. If there IS some water, removing it is your first priority.
If the fuel is OK, try running very gradually up to, and perhaps past, the problem 3800 rpm. Does the problem occur at about 2/3 throttle, or is it always right at 3800 rpm regardless of throttle position? It's possible the Quadrajet secondary accelerator system is botched. There are a couple of wells between the fuel float chamber and the secondary side. They fill very slowly through some tiny little orifices and empty quickly when the secondary air flaps are sucked open by the vacuum created at large throttle openings. All they do is eliminate bogging when going to big throttle positions. If you can gradually get to high rpms that system is the likely culprit. There are two tubes that suck the fuel from the wells. They can be clogged or installed wrong. Also the fill system could be clogged. If you end up redoing the carbs you are best off getting the correct original ones rebuilt rather than buying generic ones off someones shelf. There are correct jets and settings that rebuilders claim don't matter. But to get it right they do!

 

[tank1949]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

it is starving for fuel some way. a clogged line or carb bowl due to not having seperator is also a good starting point.

 

[ninjamatt]

Re: 4.3 stalls at 3800 rpm's, will start right back up but stalls everytime at 3800 r

i had the same problem over the weekend with my 89 4.3. for about 10 minutes it ran fine, then started bogging down and wouldn't get on plane. all I did was put some of that 20 dollar sabelizer in it. I don't remember the name but it worked. The bottle is at my friends house who knows more boat mechanics then me but basically he said it took did something to the water in the tank