TOPIC: 69 merc 125hp tower having issues throttling up.

Well I found a set of used controls form my buddy who owns CJ marine in Marsyville. Got those on. However I still am having issues that I attributed I thought to water in gas.

I could not even get motor started after back of boat where plastic 15gallon tank is located.

I changed my marine seperator. Shot out some gas that appeared to have some clear water first.

Now I can start motor most of the time and get it to idle usually.

However even on the lake yesterday I let it idle for 20 minutes. But when I try to throttle up it dies immediatly.

I am at a loss of that it might me. This is a great motor I got from Billr a few years back. Very well maintained. I did rebuild the fuel pumps about 5 years ago. Not sure but it seems like a fuel starvation problem. Thought of pulling off carbs to clean. However while I have built many a carb. The linkage of the three and springs have me alittle nervous to fool with them.

ANyone have any suggestions?
Plugs are 4 years old. But it does not seem electrical.

sounds like water in the carb to me.....

AFTER you have checked all fuel connections, hoses, etc for air leaks & are confident you have no leaks

try treating new fuel with seafoam in your tank.....remove the brass plugs on each carb to drain the fuel....tilt the motor to aid in draining...
replace the drain plugs and pump the squeeze ball with new treated fuel start the motor and idle for 10 minutes, to get the seafoam in the carbs.....shut down the motor to allow the seafoam to work

this quick fix dose not always work but I have dodged a few bullets with water & ethanol issues this way...but many times a tear down of carbs is mandatory

Thanks! Will pick up some seafoam tomorrow.


As for now, I think it may be an issue with the lowest of the 3 carbs. The one on bottom is not appearing to leak any gas when I fully tilt motor and flood with ball. The other 2 carbs leak out gas. Not the lower one.

I removed all brass fittings and the top 2 carbs spewed out gas. The lower one did not appear to dump much gas from bowl.

I can start and it idles well. I can take up in a barrel thru power band and it does not stumble. However put it in lake and it dies each time I give it gas under pressure.

I checked gas line at the lower carb and gas in is line. So it appears gas is getting to the carb. I ran lots of carb cleaner thru it while on hose.

Another think interesting to mention. When I spray carb cleaner in top carb it accelerats the motor. When I spray into middle carb it lowers rpm of motor. When I spray in suspect lower carb it very slightly raises RPM.

Initally when I squeezed bulb I got an increase in acceleration and that would point toward fuel pumps. However after it ran for awhile it made no differane and bulb had gas in it.

ANy ideas?

Maybe a piece of trash in the lowest carb's needle valve? I think you're right about it sounding like a fuel starvation problem, and please remember that's where the motor gets it's lubrication from as well. If it were mine, I'd pull the carbs for cleaning and kits IMMEDIATELY, before any damage is done to bearings, cylinder walls or pistons, etc.. If the fuel hoses on there aren't alcohol resistant, I'd replace those as well.

It's not that bad pulling and rebuilding those carbs, take your time and take lots of pics before you start and during the process. (It LOOKS more intimidating than it really is!) IMO, the biggest pain was removing all the "other stuff" to make room to get them off and on. IF yours is the same as the two I have worked on, you have to slide all three carbs off at the same time. Also, you'll have to loosen the mounting nuts some, slide the carbs out, and finish removing the nuts. Have the kits on hand, so you can put it back together while it's still fresh in your mind. (Works best for me, you may have a better memory than I!)

You can do it!

Agreed

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Inspect / clean those carburetors.

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You risk ruining a fine motor if you run with a plugged carburetor.

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After you are done cleaning them you will say " that was easy "

Interesting. I would think the carb must be passing some fuel/oil as it will idle and run thru band. Just not under pressure of being in lake. I hear you about the pain getting to them. I had to take front of motor off just to get the bronze fittings to put lower one back on. My worry is the internel wiring is not great. I have used liquad black tape to keep some of it from having outer insulation fall off. I need to get an internal harness if I ever see one.

By looking I think it would be painless to remove just the lower carb and inspect, clean and rebuild if need be.

Thanks for all the help!

You guys rock!

Tod in Marysville. WA

425 737 1243

I have been rewiring every old merc I get internaly, not too hard I jsut take the wires back as far as I can then solder new ones on with all soldered connections covered with Heat shrink tape, jsut go one at a time and it may help with some issues your having in the long run, if there is a short that vibrates right and grounds out the ignition or something.. just a thaught.. by no means an expert at all so...

This sounds like the problem I had with my fuel pump diaphram.

Not fuel pump issue. Rebuilt and still problem.