Mercury Mariner 25 HP

My son left his 25 HP S/N OC287406 setting out side in the open the past*year and a half*and it didn't want to crank. I was running OK when it was parked. He used some starting fluid to light it off but it only wanted to run*at very high RPM's. I figured it was time for another carb rebuild. I did that about three years ago...
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We found a lot of water, and junk in the bowl and the primer pump was leaking through. All the passage ways look to be clean and I can't find any stopped up, even the two tiny ones behind the butterfly are clean.*We didn't take the fuel pump off*because we didn't know if it was still pumping or not..
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After the cleaning and replaceing the primer pump, the engine will only fire off a couple of cycles when first cranking. A shot of starting fluid doen't help at all. The spark is real hot and jumps about 3/8" to a 1/2"..* When I pulled the spark plugs they are wet. Dry them off and it'll fire a couple of*cycles again and won't untill the plugs are pulled and dried again. It acts like it's flooding to easy. I checked the float height and it was still at the 1" that it was set at on the last rebuild when I also had to replace the old float back then.. I've checked the float*needle and seat and they seem to be working like they should and cutting the fuel off.
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I've pulled a few wrenches over my years but this one is trying me... I feel like I've over looked something. With all the crap in the carb it would at least run high RPM's*and die*at low, but now it doesn't want to run at all execpt the first couple of firing cycles.. What am I missing.
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Gerald K4NHN
Cayce, SC

badly fouled plugs maybe

Maybe not, replaced with new ones already.. these are the gapless type also..

Gerald K4NHN
Cayce, SC

When you say " left in the open " are you saying that the cover was off ??---------------------------Have you checked for debris in the reed valves ??

Today's update.
Raceone, I meant that the boat was just left uncoverd and open to the weather. The motor cover was on. There wasn't any indication that anything had gptten inside the motor cover like maybe a dirt dobber. I went out this AM and decide to take the plastic cover off the front of the carb and then I held the butterfly open and it cranked up but was real rough running. It sounded like it was running on one cylinder but pulling the wires off, both were working. I removed noth coils and measured them for resistance, one was 1200 ohn and the other was 1000 ohns. A little difference, but both have a real hot spark. I changed the switch box with another one that I have and it was the same.

The low speed mixture adjustment doesn't have the effect that I think it should, I can't find that good spot at about the one turn out area, and the engine will still stay running with the adjustmen all the way end. So I guess it's time to pull the carb off again and see if I can find something in there again. I haven't taken the fuel pump apart since it seems to be doing OK, I don't have to pump the bulb to keep it running. Would any leakage in that diapham make it be on the rich side?

A leaking fuel pump diaphragm would certainly result in a " rich condition "

Thanks, I'll pull it apart this afternoon in between the caution laps of the race.

Gerald K4NHN
Cayce, SC

I am watching this " caution all the time " event as well.

Now that the "8 wheel racing" is FINALLY over (booooooring) it's time to fix what's really wrong with that carb.

And the answer is....The enrichener valve is stuck open, resulting in a massive flooding of the engine that even starting fluid (gasp!) won't cure.

1. See that the plunger is not the slightest bit depressed with the "choke" off.

2. If it's not, replace the plunger mechanism after a thorough cleaning of the entire carb.

Jeff

PS: Hold on to your wallet if you need to buy a rebuild kit! Those guys should wear a mask.

Fastjeff, I think you talking about the primer diaphragm that's on the right side of the carb when you're looking at the front of the carb. I did replace that and the pump diaphragm. and cleaned the carb several times. that may have been wanting to hang up or leaking some. that was the first thing I replaced because it was in real bad shape. The low speed adjustment is working a lot better, maybe not what I think it should but the son headed to the swamp today for a week of fishing and camping.. He called this afternoon and said that it fired off with ease today and ran like it use to and hasn't had any trouble at all today. I can see where that could make it go rich or flood. We diid replace the spring with the new one. The first time we found that it wasn't working and opened it up and found that the ball was down in the spring about half way and looking at it close it looked like it was larger OD than the old one so I put the old one back in and it seems that took car of that.. I'm glad that you brought that up to me, I had overlook that. I'll be in the swamp with him tomorrow and I'll see if it's still doing OK. He's with someone else, so if it really acts up, he's not alone. I knew that the kit was expensive, on line it about $26 to $28, but locally it was $50. Mostly just a bunch of punched out gaskets, half that you don't even need... I do try and stay away from the starting fluids, usually just a sniff to see if it'll cough so I'll know if it's electrial or a fuel problem.. Don't want to wash the oil off the cylinder walls. I usually have a 50 to 1 mix in a spray bottle.

Gerald K4NHN
Cayce, SC