Mariner Fuel system

[drewpster]

I have a 115 mariner with throttle response problems. The engine stalls then recovers when the throttle is opened. It idles fine and runs at speed well. I know this engine only runs on two cylinders at idle and all four above 1600 rpm. I know there has to be an accelerator pump somewhere to make up for the lag when the engine transitions from two to four. I think, (I need to check the year model) that this engine has WME carbs. How does the accell pump circuit work? Do these carbs have pumps or is there a separate pump?
I have already gone through the basics. I am thinking the carbs need cleaning/ rebuilding. Would a clogged main jet cause this problem as well?

 

[Laddies]

Re: Mariner Fuel system

If the engine runs properly at high RPM the carbs don't need cleaning. It could be a little lean on the idle, the accel pump which is seperate from the carbs may need adjusting or to much prop will cause a lag. Here some stuff on the pump.

 

[drewpster]

Re: Mariner Fuel system

The prop installed on the engine is factory. The Clymer manual I have has a pretty good section on synchronization. You think I should make sure everything is timed properly (meaning the linkage) before getting into the pump circuit? The previous owner said he had the boat in the shop concerning this problem and when he got it back he could not tell a difference in the way it ran.
We have had rain here so I have not had the boat on the lake long enough to really know what is going on.
I have had a good look at and looks as though some screws have been turned. How difficult is it to sync this engine?
Thanks for the detail.

 

[drewpster]

Re: Mariner Fuel system

I finally got some clear time today and I took the boat to the lake and did some testing. The linkage was way out of wack so I got it set back to where the Clymer manual says it should be. The accelerator pump shows the correct position at WOT. After some mixture adjustment I got the engine idling relatively well. They were definitely set too lean. The number two carb seemed to show more response by mixture changes than carb one, but the engine seems to be in the ok range as far as mixture goes.
Unfortunately the engine is still falling on its face in the part throttle range and opening up as the throttle is advanced, no matter how fast you open it. I left the throttle in the position where it ran the worst at one point and noted that it did not change in the way that it ran. In other words, I do not think it is the accelerator pump.
You can advance the throttle in gear to just off idle and the engine runs rough and makes no power. If you leave the throttle there, the engine continues to run rough. If you advance the throttle a little further the engine will suddenly open up and run good.
I am still think some passages are plugged up in the transition circuits of the carbs. Any thoughts?

 

[CharlieB]

Re: Mariner Fuel system

You're right, the carbs need to be cleaned.

The top two carbs do not have an accel pump and the idle mixture must be set right near 1/4 turn richer than best idle to provide the additional fuel required for acceration.

The transition ports (mid-range) must be clean in all carbs as these ports pass gas immediately off idle and all cyl's fire.

If I remember correctly the correct setting for the accel pump is a measured GAP at the pump cam at dead idle. I'll have to go find the book, or take a feeler guage home and measure where I set mine.