1989 Merc Alpha 4.3ltr cutting out when @ high throttle

VermontLund

VermontLund

Cadet
Joined
Aug 10, 2012
Messages
7
I have a 1989 Lund Sportfisherman... It has the Merc Aplha I/O 4.3ltr... Since mid summer the engine started to burp (miss fire?) a little bit when I increase the trottle to bring up on plane.. When the issue 1st started, it seemed to be only cosmetic, and I didn't really have any decernable power loss.. By now, 2 months later, the problem is not going away,but getting worse... I changed my water separating fuel filter which was full of water, and it seems to still be doing it. I also added marine stabile and it seems better, but not gone. I suspect water in gas, or bad gas. This boat has a 60gal tank and I use the kicker for fishing, so I probably haven't even used up all the 60gal from winter storage yet this season. (put 5-15 gal in to top off each trip) Now problem has gotten bad enough I can feel the power loss when it starts to act up and I almost have trouble getting it to plane out!

I am interested in hearing what you guys think this could be... Bad gas, bad plug, wires? I did have a guy aboard a couple of weeks ago who said it sounded and felt like bad gas. Didn't sound like something mechanical.

I am going out on another test drive Friday after putting 4 bottles of heet into tank. Hope it clears up.


Please dont suggest draining a 60gal tank :(


Thanks for any ideas on cause and fix.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 1989 Merc Alpha 4.3ltr cutting out when @ high throttle

When was your last full tune-up and compression check? Have you checked your fuel filter water separator for water (use new filter, never reuse a filter). Timing checked and advance timing checked?

If you think it's old fuel, hook up a remote fuel tank (6 gal outboard tank) and take it for a run and see if the problem goes away.
 
D

d04pyma

Cadet
Joined
Aug 4, 2012
Messages
6
Re: 1989 Merc Alpha 4.3ltr cutting out when @ high throttle

Hello ! Check the fuel pump, had the same problem. Remove fuel pump take it apart on the backside of the diaphragm it will be full of deposits from the fuel,back side of diaphragm, follow the line to the intake of the carb. I had the same problem with my sons boat, make sure that the pushrod for the pump is up when you install the pump.
good luck !





VermontLund said:
I have a 1989 Lund Sportfisherman... It has the Merc Aplha I/O 4.3ltr... Since mid summer the engine started to burp (miss fire?) a little bit when I increase the trottle to bring up on plane.. When the issue 1st started, it seemed to be only cosmetic, and I didn't really have any decernable power loss.. By now, 2 months later, the problem is not going away,but getting worse... I changed my water separating fuel filter which was full of water, and it seems to still be doing it. I also added marine stabile and it seems better, but not gone. I suspect water in gas, or bad gas. This boat has a 60gal tank and I use the kicker for fishing, so I probably haven't even used up all the 60gal from winter storage yet this season. (put 5-15 gal in to top off each trip) Now problem has gotten bad enough I can feel the power loss when it starts to act up and I almost have trouble getting it to plane out!

I am interested in hearing what you guys think this could be... Bad gas, bad plug, wires? I did have a guy aboard a couple of weeks ago who said it sounded and felt like bad gas. Didn't sound like something mechanical.

I am going out on another test drive Friday after putting 4 bottles of heet into tank. Hope it clears up.


Please dont suggest draining a 60gal tank :(


Thanks for any ideas on cause and fix.
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