Mercruiser 4.3/LX v6 AlphaOne Acceleration Issue

[SeaSprite1700]

Hello, I was hoping to get some advice on how to fix an issue I am having. I have a 1993 SeaSprite 1700 with a Mercruiser 4.3/LX v6 AlphaOne (Engine Serial Number: 0F073016) and it is not operating properly. It will start fine, and idle great, and once I get out of the no wake zone, I give it throttle to plane, and there is almost zero acceleration. You can hear the RPMS go up a little from idling out of the no wake, but with the throttle position at WOT, the engine does not sound like it is at full WOT, nor is the boat moving quickly, probably doing around 5 MPH. I bought the boat used last September, and it worked great, I figured I'd do the routine stuff like plugs, wires, and fuel filter, but I am having trouble finding consistent info on the web on what I need to replace these parts. My uncle had a late 80's Bayliner and experienced something similar and for him, replacing the fuel filter at the carb was all it took. I just can't figure out what filter I need. I want to start with the basic routine maintenance items first. I have the 4bbl carb so what rebuild kit would I need or would a good cleaning be all that it needs?

Thanks in advance!

 

[Scott Danforth]

welcome aboard

you may have crud in the carb, you may have crud in the fuel system. sounds like the accelerator pump circuit is not working properly

there is no one-answer-fits-all.

start by checking the contents of the fuel filter in a clear container to ensure its pure gas. (replace the filter, never re-use the filter).

it may just need a full cleaning.

 

[SeaSprite1700]

Ok perfect! Would you have any clue what filter I need? I seem to find different answers and not one consistent answer. I've found that the only filter will be where the fuel line connects to the carb but I also find a screw on filter in my search online?

 

[Scott Danforth]

the filter will be dependent on which filter head was installed in the boat by SeaSprite

 

[SeaSprite1700]

Ok great, thank you!

 

[Rick Stephens]

My first Mercruiser boat only had the inlet screen when I bought it used. Many manufacturers scrimp on that since the boat will run fine until the day there is a contaminant in the fuel. I added an inline canister type filter to it before the pump. (do not add automotive filters nor inline filters between pump and carb).

Most carburetors have a screen filter right where the fuel line connects to the carb.

All it takes is a little crud in the fuel to plug up small ports in a carburetor making it run like you describe...... or frankly, like almost any description of a poorly running boat that you can imagine. At that point you rebuild the carb. The Mercruiser service manual is absolutely necessary. You can find one online at http://boatinfo.no/lib/mercruiser/manuals/mercruiser7.html

 

[SeaSprite1700]

Thank you!!!

 

[Bondo]

Ok perfect! Would you have any clue what filter I need? I seem to find different answers and not one consistent answer. I've found that the only filter will be where the fuel line connects to the carb but I also find a screw on filter in my search online?

Ayuh,..... Welcome Aboard,..... '93 is a transition period,...

Ya got either a rochester quadra-jet, or the Merc/ Weber/ Carter 4bbl. carb,....
The quadra-jets have been around forever, 'n parts can be found for 'em,....
The Merc/ Weber/ Carter is a carbon copy of the Edlebrock Performer #1409, 'n I buy Edlebrock parts, 'n kits for 'em,......

Also, if it's got the mechanical fuel pump, there's a filter inside the fuel pump,....

If it don't have a canister style filter, ya oughta add 1 'tween the fuel tank, 'n fuel pump,....

 

[SeaSprite1700]

Thank you, I will have to take a look Thursday once I can get back up to the boat.

 

[Derbytime1]

How are you making out? Have similar issues on same carb on 5.7 Mercruiser in SSV 249 Glastron. Had carb rebuilt, cleaned tank, replaced pump and filter, and still have similar results. Found that left side primary nozzle is not spraying fuel. Less fuel in that bowl as well. It is the furthest from pump, and side where accelerator pump is as well. As recommended, if your boat does not have the water separating filter between tank and pump it would be well worth the $35 to add. If I had all to do again, I would have done everything all at 1 time, which I think would have solved my problem. My tank was not fully drained the 1st time, and I believe may have created same problem within freshly rebuilt carb.

 

[SeaSprite1700]

Well, I actually have the fuel/water separating filter, so I changed that, and swapped plugs and wires, issue still persisted. Had a mechanic buddy of mine, who is by no means a "marine" mechanic, but has worked at or owned a shop for the last 20 years look at it, and his best guess, since all he did was look it over while running, and hasn't actually diagnosed anything is that he'd bet on the fuel pump, or the diaphragm in the accelerator pump. I got the carb rebuild kit for $80 on eBay, so once that comes in I will rebuild the carb. If that doesn't do it, I will swap the fuel pump. It'd be nice if this was cut and dry, and the problem was an easy fix, however this is actually turning out to be one hell of a learning experience for me, as a first time boat owner and not a mechanic by any stretch of the imagination, I have just been soaking up knowledge. The silver lining in all this once I find my issue and sort it out, is I will know the ins and outs of my boat a whole lot better, and sure, I am throwing money at parts that may have not needed replacing just yet, but I don't see any real harm in a carb rebuild, new filter, plugs and wires.

 

[kirkll]

Well, I actually have the fuel/water separating filter, so I changed that, and swapped plugs and wires, issue still persisted. Had a mechanic buddy of mine, who is by no means a "marine" mechanic, but has worked at or owned a shop for the last 20 years look at it, and his best guess, since all he did was look it over while running, and hasn't actually diagnosed anything is that he'd bet on the fuel pump, or the diaphragm in the accelerator pump. I got the carb rebuild kit for $80 on eBay, so once that comes in I will rebuild the carb. If that doesn't do it, I will swap the fuel pump. It'd be nice if this was cut and dry, and the problem was an easy fix, however this is actually turning out to be one hell of a learning experience for me, as a first time boat owner and not a mechanic by any stretch of the imagination, I have just been soaking up knowledge. The silver lining in all this once I find my issue and sort it out, is I will know the ins and outs of my boat a whole lot better, and sure, I am throwing money at parts that may have not needed replacing just yet, but I don't see any real harm in a carb rebuild, new filter, plugs and wires.

I’m no mechanic either and I haven’t got any suggestions of helpful insight to trouble shooting your issue. But I myself am in the same position as you are, and have the same issue going on an old 1990 Blue Water boat. Mine is a Mercruiser 4.3 with a 2 barrel carb, but mine supposedly has a new gas tank, and new carb. The old boy I bought my boat from was a handy man type guy, and did a lot of the work himself on this boat. He put a “ new motor, new gas tank, and new carb” in it himself.
this was great news at the time I bought it, and it ran Great! Now after having issues here and there and auto parts used instead of marine grade stuff, I called the guy back to see where he bought the “new motor”.... he says, “ I can’t remember the guys name but it’s a 1990 motor and it runs great....”. Sooooooo...l.guess I’m on my own huh?

I really like your silver lining attitude. I try to think along those same lines myself as I work the bugs out of my old boat.

But I need to pass along some advise , or a consideration regarding rebuilding a carburetor. As handy as I’ve been sorting out misc engine problems with cars over the years, I’ve never had good results trying to rebuild a carb, and I’ve tried several times and failed miserably. I believe having a pro do this for you is worth the money. There seems to be a bit more finesse needed than I posses to pull that off successfully. I just thought I’d share my own humble opinion and possibly save you some heart ache. Crudely put.... carbs kick my butt every time messing with them.....

personally , I’m going to change out my fuel filters and fuel pump first. then check out the so called “New fuel tank” pick up lines. I’m a little gun shy on mine now.... lol. Kirk

 

[GA_Boater]

kirkll Stop posting in old threads.