'97 Mariner 25 Very Rich At Idle

[hinterlander]

This is a low-hour '97 Mariner standard 25 used about six to eight times each season, lubed with Amsoil 100:1 premix run at 60:1 that has performed great since new. This year, it has been running extremely rich at low speed, will not troll down, just blows blue/white smoke and wants to stall. It runs great off idle, midrange and high speed are normal. I am running NGK BH7-HS plugs, one season old. Motor is well maintained, always run the fuel out after use. I checked the gap on the enrichener, between the solenoid plunger and the stop, looks to be about 80 thousandths. Plunger is not sticking open, the key operated enrichener works ok and retracts when released. Could this be an internal leak on the enrichener? Help! I love this motor!!

 

[tashasdaddy]

Re: '97 Mariner 25 Very Rich At Idle

could be a pin hole in the fuel pump diaphram.

 

[hinterlander]

Re: '97 Mariner 25 Very Rich At Idle

So a pinhole in the fuel pump diaphram would cause a vacuum leak and allow the engine to suck raw gas into the crankcase? Is this a common problem?

 

[hinterlander]

Re: '97 Mariner 25 Very Rich At Idle

Anyone have any ideas? Could it be the primer system "hanging open"? Sunk Float? The fuel pump diaphram idea just doesn't make sense to me, seems like I would lose fuel pressure before I would suck raw fuel into the crankcase..

 

[HSEMJ]

Re: '97 Mariner 25 Very Rich At Idle

After running the engine above idle and then returning back to idle does it take a while for the engine to start to run rich again?
If so the problem could be in the bleed system.

Also are you sure thats the right sparkplug for that engine?
i seem to remember that engine using a BP8H-N-10 but i could be mistaken.

hope that helps.

 

[hinterlander]

Re: '97 Mariner 25 Very Rich At Idle

Backing down from midrange or high speed to idle, it starts loading up immediately. Runs perfect at anything above high idle. You are correct, the right plug is the BP8H-N-10, but I troll for hours, so I used one heat range hotter plug per advice of the local dealer.

Is the bleed system the crankcase purge that removes puddling fuel? Seems like older Japanese Mariners had a check valve for that. Is that the bleed system?

I've experienced a plugged check valve on one of the older 10 hp mariners, always resulted in one fouled plug, but that motor would idle until the plug fouled.

I got my hands on a Seloc manual for this motor, and I suspect the problem may be in the primer. Appears to be a reservoir with a diaphram on the bowl operated by a lever operated either manually with the knob, or electronically with a solenoid. For some reason it may be hanging open and dumping fuel somehow?

 

[HSEMJ]

Re: '97 Mariner 25 Very Rich At Idle

The bleed system does recirculate puddled fuel. There should be 2 small rubber lines connected to the reed plate under the carb, and running down the starboard side and connectng under the plate where the shift mechanism is. A problem there would cause the outboard to load up but only after idling for a minute or so.

Now that you said the outboard loads up immediately, i don't think the bleed system is the problem.

The reservoir your describing on the bowl of the carb is a primer and i'm thinking your on the right track. If you remove the carb and turn it over you will see 2 plugs, a 1/2 hex plug and a 7/16 hex plug. If you remove the 7/16 one, underneath it there should be a small spring, and a small check ball. (becareful their small) This is a check valve that only allows fuel into the engine when the primer is pressed. You may find some dirt in the seat or on the check ball or find the ball has been pressed into the spring. This would cause the engine to be primed all the time.

And now you got the carb off, just as well go through it and give a good cleaning and look over d

hope that helped

 

[hinterlander]

Re: '97 Mariner 25 Very Rich At Idle

Yep - That was the help I was looking for. I shall give it a try. Bought the right plugs tonight as well. Thanks - I will email you and tell you if that worked next week. Go Leafs!!

 

[HSEMJ]

Re: '97 Mariner 25 Very Rich At Idle

post the outcome here Hinterland, it may help someone else some day with the same problem. d