Spitting gas out of carb when in water?

[Texas Prowler]

Hello all! I have a outboard that I am trying to get running and on the water. It's a 4hp 1997 merc 2 stroke. It will run fine when the lower isn't in water. Once in water it spits fuel and dies shortly after. Been through the carb countless times cleaning and setting the float. Compression is 90psi and it has great spark. Any ideas are greatly appreciated. Thanks!

 

[Grub54891]

Check the reeds, backpressure could be the culprit.

 

[Texas Prowler]

Check the reeds, backpressure could be the culprit.

I was thinking the same. Just needed confirmation. Or at least someone else thinking the same thing. Does anyone know what the factory compression on this engine was from the factory? I'd like a base line to compare and decide if i should just throw in a new piston ring while I'm at it. Thanks!

 

[GA_Boater]

You say you set the float, but did you adjust the idle mixture needle in the water?

 

[Texas Prowler]

You say you set the float, but did you adjust the idle mixture needle in the water?

Yes tried every position of the screw. Didn't change a thing. Sucks.

 

[jimmbo]

Is the fuel being blown out of the carb, or is it dribbling out?

 

[Texas Prowler]

Is the fuel being blown out of the carb, or is it dribbling out?

Blown/ dribbled. I like to add the previous owner had the carb replaced at a local shop and I verified this.

 

[Texas Prowler]

Ttt. Anyone know the compression spec on this motor from factory or ones you've come across?tryingto get something to go off of. Thanks!

 

[jimmbo]

I suspect the float is set too high

 

[Texas Prowler]

I suspect the float is set too high

When I originally got the outboard this was my first thought. I then went through float settings high-low with no change. Then i took it out of the bucket and put it on muffs... And it runs with no issue. And sounds good while doing so. Before coming here I googled and found others with this engine have/had the same issue, but no fixes ever posted and threads went dead. If I have time I'll pull the motor this weekend and see if I can checkout the reeds

 

[Texasmark]

Hello all! I have a outboard that I am trying to get running and on the water. It's a 4hp 1997 merc 2 stroke. It will run fine when the lower isn't in water. Once in water it spits fuel and dies shortly after. Been through the carb countless times cleaning and setting the float. Compression is 90psi and it has great spark. Any ideas are greatly appreciated. Thanks!

My service manual says when the comp is below 120 expect problems. That's taken with plugs out except for the hole you are testing and engine rolling at about 200 rpm....a good yank on the cord and at least the third pump from the piston on the meter. Fuel pump is pressure operated from the cylinder. Your low compression could be generating pressure leakage causing the diaphragm to pump excessive fuel when the lower unit is sealed from being submerged....even though you have pressure relief holes in the mid section to mitigate that problem.

 

[Texas Prowler]

This is great info here^^^ Thank you for looking up info and helping out. I really appreciate it. Good thing is the combustion wall is smooth and shiny as glass. Started taking the block apart to inspect. Just need to renta puller for the flywheel.

 

[tommarvin]

You can get a cheap puller at Harbor Freight Tools, make sure you get the correct puller so you don't damage the flywheel.
Be sure to hone all cylinders.

 

[Texas Prowler]

You can get a cheap puller at Harbor Freight Tools, make sure you get the correct puller so you don't damage the flywheel.
Be sure to hone all cylinders.

Sounds like a plan. I'll check HF THIS weekend. Maybe they will have the cylinder hone tool as well. What type of hone tool do you guys use on small engines? Rectangular stone or ball?

In doing some searching I found a guy saying he uses oversized rings to obtain a better ring gap. The pistons are obsolete and it's not a motor i want to dump cash into other then rings, reeds, carb kit and gaskets.

Anyone have an idea of what the factory ring gap should be with this block? I was thinking i might be able set the old rings in the cylinder and check them that way.not sure here.... Thanks!

 

[Texas Prowler]

No Title

 

[racerone]

Unless it has high hrs or abuse a 1997 model likely does not need new rings.------Serial # of the motor ?

 

[Texas Prowler]

No Title

Unless it has high hrs or abuse a 1997 model likely does not need new rings.------Serial # of the motor ?

06574892

 

[Texas Prowler]

Unless it has high hrs or abuse a 1997 model likely does not need new rings.------Serial # of the motor ?

Well i figured since there are no visible cross hach marks it has high hours and could use new rings. Are you saying use the old rings?

 

[Texas Prowler]

Unless it has high hrs or abuse a 1997 model likely does not need new rings.------Serial # of the motor ?

Guess I'm ideally trying to achieve a high compression here. Way over the 90psi it is now. Will a hone and the same rings achieve that?

 

[Texas Prowler]

No Title

Well guys I've got it all apart rings look to be in great shape. They were loose on the piston and clean as could be. Lots of life left i guess, but I'm no small engine mechanic lol. Looks like a good hone job will be in order and i guess I'll use the old rings. Would now be a good time to knock the knife edge off the intake and exhaust ports? Do the reeds still look ok? Thanks!