merc 115 fuel problem

[jims3000]

i just rebuilt my 115 it is a 1975 model the problrm i am having is it isnt getting fuel to the spark plug.it has 130lbs of compression and the carbs are getting fuel i can hold my hand over the carbs and turn the motor over and remove my hand and alot of gas will come out the motor is trimmed all the way down.you can see fuel comming out of the exhaust on the foot but nun is getting to the top of the piston.any suggestions without taking it all aprt again.

 

[Chris1956]

Re: merc 115 fuel problem

Jim, The only way fuel can get from the carb to the exhaust near the prop is via the cylinder. Have you checked for spark at the plugs? If you have spark, then either the timing is bad or your carbs are bad. Spray some 50::1 fuel mix into the carb while cranking. If it doesn't fire, you do not have spark.

 

[jims3000]

Re: merc 115 fuel problem

well i finally got it to run.it took alot of gas in the carbs to get it to fire.
and starts fine every time after but if it sits for a while same thing takes alot of gas to get it to fire off.the carbs work fine when running and the timming is set right any other things that can cause this thing to not want to start?

 

[jims3000]

Re: merc 115 fuel problem

also when i rebuilt the engine i used 150hp pistons they were in better shape then mine but they had a hole in the side of the pistons not sure if they were for oiling the rod bearings or what could this have a effect on the starting also.plus how can you tell if the reed valves arent sealing good,i am leaning to that being my problem.

 

[Chris1956]

Re: merc 115 fuel problem

JIm, The 150 Pistons are fine. Your block has different porting so the "Power Port" pistons from the 150 will not have any boost effect on your motor, however.

Before you blame the reed valves, check the compression. You should have 100PSI minimum on the cylinders and they should be close to one another in compression. If the compression is good, make sure the carb choke shutters close completely when the choke is pushed. Starting is easier if you over pump the primer bulb a bit to force a bit of gas into the engine. Make sure the motor is trimmed all the way down and the starter is really spinning the motor. Heavy choke is necessary.

 

[Chris1956]

Re: merc 115 fuel problem

Oh yeah, one more thing. Clean the distributor cap and rotor. The rotor is not-removeable and will cost you $200 to replace if you break it.

Check the plug leads for arcing to ground and overall corrosion. Resistance should be zero from the cap to the spark plug boots.