omc tripple cut out

[iwanajohnson]

alright here's my question. I have a 93 omc 3 cyl. It has 1985 75hp carbs on it. When I take off it hops on plain then cuts out at full throttle. If I back out of the throttle just a little bit then it will stop cutting out and run fine but when you lay the throttle open again it cuts and sputters. If I bump the electric choke it pours the coals to it and it lays down and runs but cuts and sputters when your not bumping the choke. These carbs did the same thing on another motor. What's causing this? Thanks.

[thornl01]

Sounds like either water in your fuel or some trash in the carbs.

Either way it's fuel related if the choke helps.

[jerry book]

check the float level in the carbs and the sync of the carbs and throttle linkage

[Aeroliner]

If the fuel system is clean and their is no air being sucked into the fuel line then one place you might look at if the carbs are fixed high speed jet is the actual high speed jet size. You might compare them to the old carbs. The indication you discribe seems to point to leaning out when your at full throttle. When you bump the choke it make the mixture richer and your power comes back. Only a thought.
Alan

[formeone]

at the marina we usually rebuild thecarbs toget out the crap in the cercuits,,, and especially puull the top body plug overthe idle circuits to clean and re-seal the body plug with epoxy as they can suck air threw them,,,

[Fastjeff57]

It sounds like simple fuel starvation. How about attaching a fuel pressure gage and see if the pressure falls off at WOT?

Jeff

[Aeroliner]

Good point Jeff. It might be a fuel pump issue that is causing the issue. If you can squeeze the primer bulb and it picks up this could then show that a filter might be pluged or a pump going south.
Alan

[Lil' Blue Rude]

The fuel pump is fine and the main jets aren't lean because I've put jets in them fat enough it would flood and that didn't solve the problem. It's not the fuel pump because it did the same thing when I put the carbs on my motor. My motor runs just fine with my carbs so I know my fuel pump is fine. Replaced all of the fuel lines and I know they aren't leaking. The problems started with the carbs when we started modding the motor. The more rpms we gained the worse it got.

[Aeroliner]

Anyone know if there is a rev limiter built into the ignition system?
Alan

[850cc racer]

a guy here had a simalar issue with a fishing boat, it was a needle and seat issue from memory. depending if you have the old style carbs with butterfly choke or newer style pull the carb apart flip it up side down blow air through the fuel line and lift the float up and down makre sure that the needle is seating.. dont use a compressor use a long piece of clean hose and your mouth.


with the rpm limiter if its the old school electrics with the white box its unl. if its the black box some are some arent..it will have it written on the cdi the limit

hope that helps?

[Jeff Akers]

If at anytime you hit the choke or primer and the engine speeds up ( gains RPM) you have a lean condition. clean/rebuild carbs as was said in a previous post..... then retest.

[88workcar]

If at anytime you hit the choke or primer and the engine speeds up ( gains RPM) you have a lean condition. clean/rebuild carbs as was said in a previous post..... then retest. This for sure, as Allen said also. BUT you made need to remove the needles and drill the feed hole out larger. If the main jet is larger than the hole behind the needle, you can change jets till your blue, it will never fix the problem. Keep us posted on progress and don't give up. If you don't have drills and/or are nervous to do it, send them to me, with shipping pay back to you. I'll do it for free.

[ima75man]

if your carbs have the intermediated jet, take it out of all 3 carbs, i never have run them. just my 2 cents..hope this helps, if we all wrong go buy some more carbs.........lol

[Popa Sam]

Have you tried choking the carbs individually to see if maybe there is only one that's causing the problem? If it's all three then I don't think carbs are the problem unless it's the old style carbs that have all three feeding fuel through the center carb. If one carb is causing the problem I think you will find the gasket around the main discharge nozzle not sealing, the float not dropping far enough or the main nozzle has hairline cracks in it between the holes. If you can find a set of later carbs that have the primer rather than a choke they are much better carbs. The choke plate is not there to interfere with air flow.You should not need to drill the float valve unless you are running alcohol, If the fuel pump is delivering required pressure and volume.

[formeone]

also check squezze bulb should be semi hard when running,,,and also the anti siphon valve,,, lots trouble with those over the years,,

[Lil' Blue Rude]

these carbs are the primer type. I don't think a rev limiter is going to be a problem because these motors with a jet won't pull over 6000rpms. I've checked all of the float heights before for all three carbs and they where within the recommended heights. I think they have an air leak some place I just haven't found it yet.

[Powerabout]

I'd be looking at the gasket around the main emulsion tube as well ( as Popa says)
or somebody cleaned them in carb cleaner/or 100psi of air and it ate away the emulsion tube sealant so turn them upside down and drop some loctite around the tube from the venturi side

[Detroit Whitey]

Went thru the same issue its jetted to lean. I ended up riching up idle mid and high the 3jet carbs have often done the samething to me on the56in blocks. Those motors never came with 3jet carbs at least not by all the parts books. I fought that for awhile taking the mid out does help but won't cross over as snapy if ya just open it up a bunch and it all depends on the port job also try it all that's the real way to fix it for your rig good luck
_

[Lil' Blue Rude]

I really don't think it is jetted to lean because when I've put bigger jets in the problem didn't get any better. It's acted like one carb doesn't want to feed gas right. I think it has a air leak. I'm just waiting on him to bring his boat home for the weekend for me to check it out. I don't think it has 3 jet carbs. It has the main in the bowl and a needle jet screw up top in the front. If it has a third I've been missing it.

[Powerabout]

The 56'er
had all three carb styles that I can see in the parts book
86-88 main, and air bleed
89-90 main, air bleed and needle
91 main int and needle
92-2001 main, air bleed and needle ( same as sst 60)

Make sure you are not removing an air jet and trying to make it richer

[Phil McDaniel]

Take the bowls off and check to see if one or more of the washers which go on the fuel nozzle to seal the bowls from the bodies is missing.--------- sounds like what it might be. Phil