4.3 V6 Merc suddendly bogging down and stalling...

sub1427

Recruit
Joined
Aug 15, 2010
Messages
5
Hey everyone, new to this site and did some searching but couldnt find the answer I was looking for, maybe all you boating Gods can help me out. Ive had my 21' galaxy 4.3 v6 mercruiser I/O (1990) in the water for about 2 months now, little things were going wrong, got all that fixed. Today I took her out in the Long Island Sound and cruised over to my favorite little island about 9 miles from my mooring. Anchored the boat, hung out, got back in and left the island. Got on the throttle would not go above 2800 rpm and would bog down tremendously (max speed on my boat is 22mph on the gps, today it was 9.8-6.5mph) The engine would rev up then hesitate and bog down. If I ran it WOT the RPMs would go from 2800 to 2000 then rev itself back up in very nauseating, head jerking, almost stop and go. Lets just say the 9 mile ride back was not very fun. If I put it in neutral i could slowly get the engine past 5000k but it would make a noticeable sucking sound and bog, cant just go full throttle or it would stall. this is the 2nd tank of gas in it, its fresh gas so Im stuck on where to start. Any help would be greatly appreciated. Thanks in advance :mad:
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,366
Re: 4.3 V6 Merc suddendly bogging down and stalling...

Ayuh,... Welcome Aboard,.... My 1st guess would be, ya got a dose of Water in the fuel....
When was the last time it had a Tune-up, 'n Service,..??
 

sub1427

Recruit
Joined
Aug 15, 2010
Messages
5
Re: 4.3 V6 Merc suddendly bogging down and stalling...

Not sure, just bought the boat this season, its very strange, ran very well for the 9 mile run out then just shat the bed coming home, the tank is getting low its under a quarter of a tank now so that could be issue maybe, Also the last tank i ran injector cleaner and some sea foam through and it was also higher octane gas (89) since we filled her up at the pump not on the water. What can I do to get the water out? Or do I have to just drain it all and discard it? I dont know how water would get in there, my gas cap screws on nice and tight and the O-ring is in good condition. Any thoughts?
 

twostroke87

Petty Officer 2nd Class
Joined
Nov 15, 2008
Messages
137
Re: 4.3 V6 Merc suddendly bogging down and stalling...

First step would be to actually verify this is water in your gas, before you go crazy trying to figure out how to get water out of your tank.

You need to take a fuel sample into a clear bottle, if the gas is good it should look very similar to green tea, clear with a greenish/yellow tinge to it.

Any water in it the bottle will look foggy kinda like Sunny D, if thats the case let it settle to the bottom and see just how much water you got, also look for debris.

Go from there.
 

MPII

Petty Officer 1st Class
Joined
Aug 1, 2010
Messages
219
Re: 4.3 V6 Merc suddendly bogging down and stalling...

My 1992 Rinker 4.3 did the same thing. As it turned out, the Y Pipe was leaking, spraying up water, and sucking it in the intake causing it to bog. down. I agree with these two gentlemen.
 

6meter

Chief Petty Officer
Joined
May 15, 2010
Messages
525
Re: 4.3 V6 Merc suddendly bogging down and stalling...

You'll need to do alot more diagnosing to fix it. Is it fuel related or ignition related? Possibles could be dirty carb, plug wires arcing, dirty plugs, bad coil, bad fuel, anti siphon valve to start with.
 
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