97 mariner surging

[captbjack]

hey guys new to this forum but i have a 97 mariner 115 runs perfect at idle and low rpm but when it gets around 4000 rpms it starts surging. i have replaced the plugs and have good gas in it. anyone have any ideas?

 

[Don S]

Re: 97 mariner surging

Carbs may have some issues. May be due for a rebuild. May also be restricted fuel to the carbs.
Here is a Merc Service bulletin on the subject.

Service bulletin 99-5

 

[captbjack]

Re: 97 mariner surging

thanks for the info will do some testing tomorrow maybe

 

[captbjack]

Re: 97 mariner surging

forgot to mention the fuel bulb does not stay hard should it at wot?

 

[Don S]

Re: 97 mariner surging

They don't stay hard after pumping up originally. When you use fuel, the fuel pump draws THRU the bulb and it acts more like a wide spot in the line, and not a pump.

 

[limblines]

Re: 97 mariner surging

Might also check out your fuel pump easy check have someone pump it while your in that rpm range and see if it stops surging if it does more than likely its the fuel pump.

 

[gss036]

Re: 97 mariner surging

Check you water/fuel seperater filter. If it is almost full of water, there is not enough gas available to run the engine.

 

[captbjack]

Re: 97 mariner surging

thanks guys will try some of this stuff as soon as i get home at a reasonable hour.

 

[Mazda3GT]

Re: 97 mariner surging

Ive seen it before where some guy used silicone to repair the float (for gas guage). Anyway obviously the gas eats away at the silicone, it became free from the pump, when the guy was hard on the throttle the boat would bog down because the fuel pump was sucking in the silicone sludge and therefore the engine was starved of fuel. Im no mechanic expert, but am having fun learning, but to me it sounds like a fuel issue, something is restricting it.