1999 15 HP Flooding

I have a 1999 15hp, 4 stroke. I just rebuilt the carb. The engine will start but will begin leaking gas out of every possible location on the carb within 10 seconds and soon dies.

I can't adjust the float level as the float is non-adjustable. The needle is brand new. The kit did not come with a new seat.

I am stumped. Too much fuel pressure? Other? Can anyone give me a direction to at least check?

Re: 15 HP Flooding

Agree, you can't adjust the float, but did you measure to see if it was within spec's.

If not you "must" replace it.

And it could definately be the cause of the flooding...

Re: 15 HP Flooding

Well since I replaced the float yesterday, I'm thinking maybe another issue.

Wondering if there some kind of pressure relief for the fuel pump? The carb just can't use as much fuel as the pump puts out. Maybe there's some kind of vent or return fuel line that's plugged.

This baffles me and I've worked on engines for 30 plus years. This is so simple. I must be over looking the obvious.

I'll recheck the float measurement again but if you come with anything, feel free to forward.

Re: 15 HP Flooding

Here's waht I do when I mess with a troublesome carb: Pull it off the motor, rig up the fuel hose to the carb, and pump the bulb. Does it leak? If so, dump the gas out and drop the float bowl (or pull the cover on older ones). Lower the float level 1/8 inch and try agin. Still leaks? Drop it another 1/16 on and inch and try again! When it behaves, put her back together and go boating.

Jeff

Re: 15 HP Flooding

Unlike an electric fuel pump which "will" force gas, these pulse driven diaphram pumps just won't pass the gas along if there is nowhere for it to go - so really don't think it's a pressure problem.

I would follow Jeff's suggestion.

No matter how careful you were something silly, like the needle valve slipped off it's hook etc, could be causing the flood...

Re: 15 HP Flooding

Thanks for all the ideas. Here's the deal, I pulled the carb off again. Measured the float as per the attached spec and it's dead nuts.

Now I understand the whole adjustment per Jeff, but how do I do this with a plastic float? The needle slips under a little plastic tab and that's it. No way to bend the plastic without breaking the tab off I imagine.

To make matters worse, there appears to be another issue. It takes all I have to pull the recoil over. I mean two hands, standing and full body weight. It's like it's building compression but it has no where to exhaust it. A few times the recoil just stopped as I was pulling. Had to retract the rope and start over. Once the whole engine lifted & tilted forward. Now that's not normal. And boy does my back hurt.

I removed the two spark plugs and it pulls easy. Any thoughts on the float or the recoil issue guys? I really want to go fishing.

Thanks.

Re: 15 HP Flooding

Does the primer bulb get hard when you squeeze it, so is the needle initially shutting off. what is your serial number.

There is a rubber plug that gets installed above the mid-range jet if I recall it is held in by the float bowl did you get that reinstalled. Mercury uses an idle-air jet under that flat stainless vent plate on the top with the rubber gasket and that jet usually stays attached the rubber when you pull the plate off it looks like a small very small jet with a star or cross shape on top and it is just sitting in the carb. Is it in there.

Did it have the accel pump on the side of it. Did you press down on the plunger side of the accel pump in the float bowl and make sure that was not sticking.

Re: 15 HP Flooding

Yes the primer bulb gets hard after squeezing it. Serial number 0G834927

I have attached a picture of the carb. Can you tell me what number you are talking about when you mention the rubber plug?

Accel pump plunger is working free. No binding or sticking.

This morning I blew compressed air into each cylinder. The engine is in a barrel of water. The air bubbled out the prop from each cylinder. I did this to check for restrictions in the exhaust. I can't figure out why it's a real bear to pull start.

Thanks for your help.

Re: 15 HP Flooding

Number 11 is the rubber plug and #7 is the idle air jet I am referring to.

rgds,

Dave

Re: 15 HP Flooding

Dave, please find attached an image of the top of the carb. From what I can tell, there are two brass jets in the lower right. Is one of these #7?

I am removing the carb in a few minutes to check for #11.

Thanks

Re: 15 HP Flooding

Do you still have the rubber gasket you removed from there can you post a pic of the underside of it. See the brass part to the left of the big air passage you just see a little bit of that screw is that screw capped off in the side of the carb. See the bis opening in the carb to the left of the lower screw hole in the picture. but the parts listing is saying #7 is a screw in your case, i can't find a part number for that jet even up to the 25 3 cylinders 3 carb motor.

I need to see the bottom side of that gasket to see if there is an imprint of the jet on it or not.

rgds,

Dave

Re: 15 HP Flooding

Dave,

The brass screw is not capped off. In fact a new one came with the rebuild kit which I install with a new o-ring.

The image attached is the gasket and top cover. The gasket shown faces down on the carb. In other words, the image I sent before mates with the gasket surface shown. The metal cover is shown on the right.

I did find this number stamped on the side of the carb: 68L 108DE

Does this help?

Re: 15 HP Flooding

Let me look at the tohatsu books tomorrow and see if I can come with up something, by looking at the gasket it does not look like your carb has that jet, it is usually used if the idle air screw is not there but your is and not capped off surprisingly. Tohatsu does not use that jet only merc that I can tell. if it had it you can clearly see the imprint of the cross on the rubber. I am confused as to what #7 is in the drawing though and it does show it on my merc parts look up as well but not in the manual strangely. if you put a hose on the fuel inlet and hold the float closed can you blow any air into the bowl at all. I am starting to think you either have some dirt in the seat or the needle is no good. but if it is seating there has to be a gasket or seal missing in the carb somewhere, like the OMC that have that stem gasket that seals against the float bowl if not there they will flood at high speed and just die.

Was the rubber plug installed on the jet in the bowl.

Re: 15 HP Flooding

To the best of my knowledge, I did not see any rubber plug. Inside the bowl there are two brass fittings. Look like metering jets right in the middle of the float chamber area.

I hooked a fuel line up to the carb and connected the other end to a large funnel. I poured gas in the funnel and nothing leaked from the carb. No pressure but gravity feed.

Since I have an extra float (the original) I took it and bent the plastic tang up, thus raising the needle into the seat sooner. I still have the new float but I removed it to try the bent float version. Plus when I put the float in, I noticed when I raise the float manually, I can feel the needle pressing against the seat. Before I could not.

I put the carb back together and pulled it once and it starts. No flooding. It sat there and idled like brand new. I shut it off and started it again. No flooding again.

Now my only concern is will the carb get enough gas at high rpm's? Since the engine is out of the water I didn't want to raise the rpm's much above idle for lack of cooling.

Going to try running it Friday in a garbage can of water so I can raise the rpms. What do you think?

Re: 15 HP Flooding

Yes there are two jets in the middle, one is the high speed orifice which passes into the venturi or throat of the carb the other is smaller and I am positive that is where the plug should go.

But if it is sealing on the needle and you have no flooding the small needle is for slow to mid-range speed so you should be safe to put some r'sss on it, I would not go nuts in a tank though.

I did not get a chance to look at my Tohatsu books today but will on Monday.

Dave

Re: 15 HP Flooding

Started and ran again on Friday. No flooding. Did not run much past 1/3 throttle with plenty of water pass through. Shut down and all looked good. replaced the in-line fuel filter and spark plugs.

Just for the heck of it, I looked at a new Honda 15hp over the weekend. Big money. Maybe a few years from now I'll consider it but for now since this engine has so little run time on it I'll run it through the summer and hope the flooding is gone for good.

Re: 15 HP Flooding

Dave,

Thanks for all the advice on this. Going to take the boat to a local lake and run it so I can get the rpm's up. Will check back with the results.

Re: 15 HP Flooding

Crankbearing,

Ran the boat over the weekend. All went well. No flooding upon 4-5 starts throughout the day. Had to adjust the idle a little after the carb rebuild but after that it was fine.

I know it's not the method of choice but by bending the plastic tab on the float I was able to raise the float a tad and the flooding has stopped.

Thanks again for all the help.

Happy boating.