trouble with motor in water

[boatguy123456789]

hey i have a 1987 mercury 90 hp 2 stroke ob.you can start it and run it out of water and it runs fine in gear but when its in water and you put it in gear it will just bog and only go like 5mph. could this just be my plugs are bad?

 

[Bob_VT]

Re: trouble with motor in water

Welcome to iboats

You need to verify the spark on ALL cylinder's. A motor will "sound" fine when on muffs or in a bucket and will even sound smooth but.... you may not be firing on all plugs.

 

[JB]

Re: trouble with motor in water

I agree with Bob. Most commonly you have one or more cylinders that are not making power; maybe spark, maybe fuel.

Another common cause of this "runs great with no load" problem is the throttle failing to open all the way or advance the ignition timing all the way.

 

[cjleigh]

Re: trouble with motor in water

I agree with Bob as well. I ran into this same problem with a 6Cyl Merc that I had. Ran fine on the muffs but terrible in the water in gear. Turns out a cylinder was not firing due to a bad wire. I replaced the wire, and all the plugs just for poops and giggles, and she ran great after that.

Let us know if this solves the problem.

C.J.

 

[boatguy123456789]

Re: trouble with motor in water

i put 6 new plugs in it and a new fuel filter. it runs better has a little trouble starting and when you put it in gear and give it a little gas it it skips and dosent run good. if you give it alot of gas it bogs for a bit then it runs better but skips alot and seems to have trouble runing

 

[boatguy123456789]

Re: trouble with motor in water

and i also want to get a new prop for the motor and if anyone knew what pitch the prop is

 

[Mi duckdown]

Re: trouble with motor in water

Hold the phone.
First check compression on all clylinders.
2nd make sure you have spark on all cylinders.
3rd Buy an OEM Merc Manual for the motor.

 

[boatguy123456789]

Re: trouble with motor in water

i have spark on all and compression is good on all too

 

[Mi duckdown]

Re: trouble with motor in water

What is the compression on all of the cylinders?

 

[boatguy123456789]

Re: trouble with motor in water

all the cylinders are at 110

 

[boatguy123456789]

Re: trouble with motor in water

now i have replaced all fuel lines cleaned all the carbs new fuel filter and rebuilt the fuel pump annd ran fresh gas with seafoam and the problem is still there it runs a little better but still bogs and skips like it wants to go then all of a sudden it will just come back to normal and take off and run mint till you bring the idle back down again then it does it all over again. anyone help?