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Early 90s Mariner 2-stroke 15 hp "bogs" on acceleration

P

Punter

New member
Good morning. I have been lurking and learning on this forum for a while now and am grateful for all of the anonymous advice I have garnered.

My early 90s 15hp Mariner 2-stoke idles fine but dies on throttling up. If I quickly go back to idle I can keep it running. I am able to potter along at a very low trolling speed but that is it.
  • I have rebuilt the carb and changed the plugs. I wonder if the carb float could be an issue though? Seems fine to me as does the needle but I am reaching for ideas here!
  • I suspect there is an exhaust leak and am contemplating removing the powerhead to change the powerhead gasket (Motor runs better with cowling off)
  • I have also noticed some excess water pooling in the motor well on the left side of the engine but think that may just be splash from the telltale (though not certain).
  • I recently change the line from the gas tank and cleaned the fuel filter. I don't see any reason why the fuel itself would be an issue.
If anyone can share their thoughts I would appreciate it. It is a high miles engine so maybe I am just facing a full replacement.

Thanks
Bill
 
I have a 1990 Mariner 15 hp 2 stroke and have similar problem. Rebuilt carb and cleaned filter and have new fuel line. Going to replace the vacuum line that connects at the bottom of the carb to power the fuel pump. Wonder if maybe loosing pressure at higher rpms, may cause the hesitation.
 
Usually the low speed jets are opened until the engine will take the throttle and go with it. They start with something like 1 1/4 to 1 1/2 open and then if that bogs, slowly open them up 1/8" (just a little) at a time till it takes hold and runs.
 
JHack said:
I have a 1990 Mariner 15 hp 2 stroke and have similar problem. Rebuilt carb and cleaned filter and have new fuel line. Going to replace the vacuum line that connects at the bottom of the carb to power the fuel pump. Wonder if maybe loosing pressure at higher rpms, may cause the hesitation.
Click to expand...
Did it work? I am changing my sparkplug leads too. Thinking the coil end of one is fragged.
 
Update: I changed out the spark wire leads and seems to have made a significant difference. Fires up first pull and idles much more comfortably. I have yet to run it in the river under game day conditions so will wait and see how it accelerates. One of the leads I changed had to have the coil end recrimped and I do not think the spark was arcing properly. The news ones cost$65 Canadian pesos for the pair
 
Good on the carb and plug work. Check for exhaust leaks and thoroughly inspect the fuel system. Compression test could reveal more. Best of luck!
 
Was speaking with a mechanic and he said to run it under load and, when it bogs, pull the choke. If it improves it is a fuel issue, if not it is worth continuing to follow the electrical route. Think I am going to replace the coils anyway since I did the spark lines.
 
I'd suspect a fuel delivery problem too. I had a similar problem with my 2-stroke Merc. I temporarily removed the fuel line that goes between the output side of the fuel pump and the carburetor and replaced it with a piece of clear vinyl tubing, then ran the engine in a garbage can full of water (with the prop off of course) and watched the fuel flow in the tubing. My issue ended up being the fuel pump diaphragm. It had dried out and was cracked and couldn't keep a consistent supply of fuel to the carbureator. Another telltale sign was the extreme amount of smoke blowing out of the exhaust. I guess that was from raw fuel passing through the crack in the diaphragm on the vacuum side and getting drawn directly into the crankcase enriching the mixture.
 
Thanks. I have changed the fuel diaphragm and don't think that is the issue. Appreciate though that fuel could still be part of the problem - it does smoke like a chimney. I am going to run down the coil side of things and should know more after the weekend.
 
Was out this weekend and think the coil change made a slight improvement in that it seems to run better at speed but still not maxing at top end. Now going to check timing.

The other issue I am puzzled by is that it starts first pull but takes a lot of effort to get it to start again once you shut it down and try again 30 minutes later. I take the cowl off and try and catch it with the throttle manually so that when it splutters I can get it to keep going. No idea why that would be.
 
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