Losing power at full throttle.

[hermit7]

I am resubmiting this in hopes to get another opinion to my other post "Mariner 8m Carb Trouble" I wrote on 4-30-2006. I forgot to mention that in neutral I can get it and keep it running smoothly at full throttle. It is when I put it in gear and open her up that she takes off and then boggs down. I was wondering if it flooding?<br />My original post from 4-30-2006:<br />"My father recently gave me a boat and motor that had been sitting for about 10 or 12 years. The boat doesn't leak but my problems are with the motor. I changed the plugs and to my suprise it started on the 3rd pull. Unfortunatly it was pissing gas out of the top of the carb so I pulled it off and gave it a good cleaning. I got the float and needle de-gunked and it runs like a dream. This morning I took the boat out to see how it would run. It goes great at idle and mid-throttle but when you open it up it takes off and then boggs down. I was wondering if I may have the carbs air/fuel mixture wrong? I tried to adjust it but I don't really know how to do it correctly. I was also wondering if the gas/oil mixture was wrong. I have it at 50:1. The motor is a Mariner 8M ser # 667s054412. I tried to call the local"

 

[andy6374]

Re: Losing power at full throttle.

50:1 is correct.<br /><br />Check for spark on all cylinders and compression.<br />If that's ok...it's on to the fuel system<br /><br />You disassembled the carbs and cleaned them with carb cleaner right? Did you blow out all the orfices with compressed air and reassemble with a new gaskets? You should have.<br /><br />Try pump the primer bulb while attempting to get to WOT and if this helps then its time for a fuel pump rebuild.

 

[deejaycee_2000]

Re: Losing power at full throttle.

Sounds to me like it is the fuel pump diaprham

 

[MercFan]

Re: Losing power at full throttle.

I'd also go with fuel pump diaphrams and non-return valves in the pumps<br /><br />Verify this by pumping you hand primer bulb while at full throttle. If it picks up while you're pumping by hand, it's the diaphram pumps that are shot.

 

[booger man]

Re: Losing power at full throttle.

HAD THE SAME PROBLEM WITH MY 115 MERC, ANYTHING PAST 4200 RPM SHE WOULD DIE OFF AND SOMETIMES QUIT PULL BACK ON THE THROTTLE AND SHE WOULD PICK BACK UP....REBUILT THE FUEL PUMP,DIDN'T HELP...TURNS OUT IT WAS THE CHECK VALVE FROM THE FUEL TANK WAS WORN OUT AND STARVING OUT THE MOTOR,REPLACED IT AND NOW I GET 5500RPM AND SHE PURRS LIKE A KITTEN,WORTH A SHOT.....

 

[Texasmark]

Re: Losing power at full throttle.

The guys are pointing you to a fuel starvation problem.....so anything that can starve your engine for fuel is suspect.<br /><br />Since you are loosing top end, what would help, but you probably don't know, is whether the whole engine is shy on fuel, or part of it; i.e. is is a supply problem, or a carb problem.<br /><br />I agree on the bulb. That should eliminate all of the supply (tank, line, bulb, filters, and fuel pump) if the engine runs bad while you are gently squeezing the bulb at your WOT, then go after your carbs.<br /><br />Otherwise you go after supply.<br /><br />And when you are done, put some Sea Foam in your gas to stop that crud from building up in your engine caused by varnished fuel. Directions on the can.<br /><br />Mark