Terrible running 1999 Merc 90 hp 3cyl 2stroke

[Racerjoe]

i bought this pontoon boat from a small dealer several months ago. It ran ok but did not idle too well had to have uupat 1250 or so other than thst it seemed to run ok. 1999 90hp 3 cyl 2stroke. OG935846. After sitting a few weeks it really did not want to idle so i pulled the front plate off and saw gas running out of the bottom carb. I pulled the carbs and the bowls had a lot of black particsls in them. I purchased 3 kits and replaced the needles, gaskets and cleaned everything very Good. Put everything back togethr and gas was coming out the front of both lower carbs. Had also replaced plugs. Put an inline gas filter between the bulb and engine. Since then I have replaced fuel line/bulb/fitting, cleaned carbs again, new needles (seats cant be replaced), rebuilt fuel pump, all new fuel lines on carbs, new inline filter between carb and fuel pump, set floats at 9/16 (seam on floats were level when held upside down).
runs awful.... have to pump the thottle several times and have to put at 3/4 wide open to get it to crank. Needs to run about 3000 rpm to keep running. Can back off a little and it will hunt between 1500/2000 to 3000 rpm. The 2 bottom plugs are as white as when I put them in (makes me think either no fire or water getting in the cylinders and cleaning them extra clean. I swapped the top and bottom plugs and the one that was dark became lighter.... the center one is still clean as can be. ****Note: this post goes with the one about identifying the linkage I cant figure out where it goes (I just posted it a few mins ago). I am going to try to podt a couple of pics and video to see if anyone has any ideas. ***Note the white liquid at the front of the carbs????? I have not done compression test yet .. it is next on my list along with checking for spark on bottom 2 cylindrs. I live an hour away from boat so itf I forget a tool it has to wait until next trip. Any ideaa???

thanks
Les

 

[Racerjoe]

Pics from original post

 

[Racerjoe]

Cant upload video

 

[racerone]

Start with the compression test.----Is oil injection in service , yes or no ?

 

[Lewis1111]

Always, always START with compression and spark test...Could save yourself allot of time/money and headaches. Once you have verified those items you always want to make it is sparking while the engine is running. You can use a pair of insulated pliers and remove the plug leads 1 by 1 listening for a change in rpm.

Did you end up fixing the fuel issue running out from the front of your carbs? Not sure I read that; if not make sure that gets resolved as well. You wouldn't be the first person to have to remove rebuilt carbs and or the fuel pump to check everything over again.

 

[Racerjoe]

Compression test:
Top - 122
Middle - 122
Bottom: - 118

Spark is on all 3 cylinders but really looks kinda weak to me

Oil injection is in service

 

[QBhoy]

Is it charging from the stator ? Test the voltage and amps output.

 

[flyingscott]

Go back through the carbs and make sure everything is set correctly. Check for spark again. It sounds like you did not assemble the carbs correctly. A cylinder that is flooding from to much gas will have a clean plug. Do you have the correct manual for your motor.

 

[BrettNC]

Is that clean plug wet with gas when you remove it? If not, then carb completely faulty or water intrusion from bad head gasket.

 

[flyingscott]

Is that clean plug wet with gas when you remove it? If not, then carb completely faulty or water intrusion from bad head gasket.

There is no head gasket on that motor!

 

[racerone]

Agreed, no head gasket to leak on that motor.----Clean plug means ----No fuel / too much fuel.----No spark .---No crankcase compression.----Perhaps a cylinder sleeve out of position and blocking the ports !

 

[BrettNC]

Ahh, that's right! Forgot this is a blind hole motor.

 

[Racerjoe]

I am pretty sure the carbs are correct. I have messed up on a carb or two in the past but I have gone back through these 3 times. (but I agree it sounds like the floats are too high or the needles are not seating). I have put this one on hold until I can get the other pontoon's sterndrive fixed and get it off the trailer and get this one home where I can work on it. I will check stator, see how far the spark can jump, figure out what that piece (linkage) is I am trying to identify in another post, then if those do not get it I will lower the float levels and test before I start digging in any deeper)

 

[Racerjoe56]

Carbs were correct, I was pretty sure they were as I had already checked them a second time before posting this. But I did go ahead and blew everything out again last night while I was in the garage getting the other parts cleaned up and ready. I have not had it in the water yet but in the driveway it runs great. It was running so bad at the lake I had to paddle it to the launch. Put in a set of reeds and "intake" gaskets and it blasted right off.