115 Mariner doing better, but not right yet

[Cadwelder]

I appreciate all the help I've gotten from this forum. Down to only one problem now.

This is a 1987 115 HP Mariner In-Line 6. Got the starting and idleing problem solved, and it comes out of the hole great. Now after it runs at WOT for 15 - 20 minutes or so it start bogging down as if it's starving for fuel. I've checked the fuel tank pick up and it's clear. Replaced the fuel filter and fuel pump, primer bulb and all fuel lines, but the problem hasn't changed. Even checked the filter in the AutoBlend unit and it's clear. Could the AutoBlend unit cause this?

When it starts bogging down it doesn't miss (like ignition or misfiring) it just as if you've backed off on the throttle. It never dies completely and if you leave the throttle open it will pick back up and then back down. Once the engine cools off completely you can start the entire process over again.

Am I looking at the wrong problem? Could it be the ignition system. I did check the ohm values on all the ignition componets and they all check within specifications. It's not a distrubutor system, it has a trigger with indivinual coils for each cyclinder.

Thanks

 

[Dave1027]

Re: 115 Mariner doing better, but not right yet

Have somebody squeeze the primer bulb when it bogs to see if it's fuel delivery.

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

We did trying pumping the primer bulb, but this is odd and I should have mentioned it, when the bulb was pumped the engine picked up for a bit but the primer bulb stayed collapsed until the engine returned to idle then it "popped" back to orginal shape. In other words could only pump it once.

 

[Dave1027]

Re: 115 Mariner doing better, but not right yet

Try it with the gas cap off the fuel tank. Also try removing the anti siphon valve.

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

Will try with the cap off, it doesn't have an anti-syphon valve. It is and interal full tank with a vent hose, never thougth to check that vent. Will let you know how it goes. Could it be a bad primer bulb, even though it's new?

Thanks,
Dave

 

[Dave1027]

Re: 115 Mariner doing better, but not right yet

Could it be a bad primer bulb, even though it's new?

I seen posts here of people having bad results with Walmart brand primer bulbs. The guys in the know here say Merc brand is mandatory.

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

Hey thanks, I checked the venting and the tank vent is wide open so no problems there. The new primer bulb is a Yamaha, the dealer said they were better, I guess because he doesn't sell Mercury ones. Anyway, I'm down to the new primer bulb. I'm going to try a new Mercury and see how it goes will keep you updated.

Do you think it can be the primer bulb itself??

 

[Dave1027]

Re: 115 Mariner doing better, but not right yet

You'd think a Yamaha brand would be OK. Are you sure there's no crap in your tank clogging the thing?

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

Positive, I took the tank out completely and cleaned it then, filled with fresh gasoline, I check the pick up tube in the tank and the tube and screen are wide open.

What got me was when I squeezed the bulb when it bogged down it picked up for a second, but the primer bulb stayed collasped and I couldn't pump it anymore.

 

[Dave1027]

Re: 115 Mariner doing better, but not right yet

The hoses from the bulb to the tank not clogging? The bulb should refill with gas. Could be a bad bulb or something is stopping the gas coming from the tank.

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

Nothing blocking the line, that's for sure. However last night I decided to install the old primer bulb and investigate throughly. As I said the primer never really got "firm" like I'm use to no matter how much it was pumped. I took the line loose at the fuel pump and gave it a squeeze, after a couple pumps gasoline came shooting out of the line as it should. Now could this thing have been air locked? I haven't gone to the water yet, but at least the primer bulb is firm again like it use to be. I know it was getting some fuel or it wouldn't have run for the 15 to 20 minutes before it starting cutting up.

I took the primer bulb apart to see the inner workings and geeeez how simple can you get, a squeeze bulb and two one way check valves. Other than a leak I can't see much to go wrong there anyway.

 

[Cadwelder]

Re: 115 Mariner doing better, but not right yet

Thought I'd let everyone know I found the problem. I checked the primer bulb and found nothing wrong, but when I took the line loose at the fuel pump and squeezed the primer only a small stream of fuel came through. The problem was in the quick disconnect of the motor. I haven't tried taken it apart yet, but I just took the fuel line directly to the fuel pump and all problems are solved. The outboard hasn't bogged down since. Thanks for all your help and I hope this answer helps others in the future.

Dave