Merc 3.0 LX Intermittent Cut Out

[blued]

Hi all

I have a 1992-1995 Mercruiser 3.0 LX. At the weekend after planing through some choppy water for about 10-15 minutes the boat bogged down and cut out. It restarted and cut out again several times. After about 20 minutes of it starting, and then cutting out when giving some gas, it was fine. I had to pump the throttle and then feather it to bring the revs up a few times to keep it running but then it would die when I put it in gear. Its almost like the choke has closed but on checking it hasn't. When I got going I kept the speed low through the chop and then when I got back on to calm water all was well as if nothing had happened. I did varying speeds, WOT etc.

Now I had this problem last year and thought I'd found the cause. Inside the bowl of the carb was gummy stuff which was partially blocking the jets preventing fuel getting through (I assume previous owner didnt treat the fuel at winterisation). Without removing the carb I cleaned it out and didn't see any further problems for the rest of the season. I treated the fuel at the end of the season and also gave the carb a good clean out with some cleaner at the start of the season just to be sure.

The boat had a new fuel pump last year, water separating fuel filter, spark plugs, rotor arm, distributor cap and there is good compression across all cylinders. When this happens and I remove the plugs all are sparking.

Does anyone have any idea what might be causing this? Fuel starvation?

Also sometimes it will stall at idle, I think due to flooding and at others it will idle perfectly for as long as you like. I'm not sure if this is related? Most likely that my idle mixture is slightly off.

 

[ENSIGN]

Re: Merc 3.0 LX Intermittent Cut Out

Empty the water sep filter into a clear jar,let the gas settle and check for any water at the bottom

 

[blued]

Re: Merc 3.0 LX Intermittent Cut Out

Yes I'll do that this evening after work, I meant to do it last night!

Do you think it could be as simple as water in the fuel?

 

[tschmidty]

Re: Merc 3.0 LX Intermittent Cut Out

Yep. I have a private theory that when I am banging on choppy water and in general running around I stir up bad fuel and causes it to run a little off.

 

[fat fanny]

Re: Merc 3.0 LX Intermittent Cut Out

I basically have the same package as you and really never have experienced this issue but for the most part I would lean toward a fuel starvation issue and or water getting into your fuel via vent and or into your fill cap but that's a big if! Go through your hole fuel delivery path starting at the draw tube in your tank check the screen then the anti siphon valve for sedament or debre also blow back through your vent tube to ensure it's not obstructed. Were yoour plugs really clean when you removed them that would be a sign of water getting into your fuel delivery path? also make sure your fill cap seals tight. Another thing to check would be the distributor cap for moisture it's possibility aand something I have had an issue with in the past after dewinterization use WD40 to disapate the moisture from the cap if so. A couple of good things to remember when these issues arise are Fire and Fuel it's what you need to run! and what messes up Fire and Fuel H2O. Good Luck and hope this helped.

 

[blued]

Re: Merc 3.0 LX Intermittent Cut Out

Good call on water in the fuel. I emptied the filter and 95% of what was in there was water! Next I drained the tank and there was a bit of water in the bottom so have given it a flush with a bit of fresh fuel and left it in the garage to completely dry out. I'll get a new filter because there was a little corrosion round the top.

Should there be a one way valve or similar on the vent pipe? The vent on the side of the hull was pointing up a bit so I've changed this so the holes point down. Still think it would be possible for water to get in there.

Thanks for the other suggestions fat fanny, I'll go through them when I put it all back together tomorrow.

 

[fat fanny]

Re: Merc 3.0 LX Intermittent Cut Out

Blued on my 96 SeaRay the fill cap and vent are a unit and seal with a rubber groumet excpt the vent hole but the vent hole is covered and allowed to breath by the cap itself with a lip that prevents any intrusion of water you my want to look into one especially if your getting water up over the rail that was most likely the path of intrusion unless there was water in there from condensation over the winter?.But anyway finish the rest of the fuel delivery path and have fun hope this helped good luck!!!!!!!!!

 

[blued]

Re: Merc 3.0 LX Intermittent Cut Out

I got the tank back in last night and have re-routed the breather hose so it now comes in and up at a 45 degree angle. No water is getting in to the tank that way now without the boat sinking first! All fuel piping looks ok. I put some fresh fuel in last night and ran it for about 10 minutes. I'll get the filter off tonight to check it is clean and then I should be back in business

I put a fuel treatment in over the winter and brimmed the tank to the point where some fuel came out the breather so I would hope condensation didnt get in. The thing is I had this problem last year when I was on choppy water so the water could have been lying in the bottom of the tank since I bought it. I got it in March and it hadn't been used since the previous season. There was only half a tank of fuel so it's likely condensation could have formed then.

 

[ENSIGN]

Re: Merc 3.0 LX Intermittent Cut Out

This is a growing problem,I wish I could figure out how to make water burn!