1986 mercury 115 2 stroke inline 6 bogging at full throttle

[popknot]

My 86 mercury 115 runs great for about 30seconds out of the hole then it boggs down and will only run about 3000 rpm and will surge some. Go back down on the throttle and wait a bit and it will do it again. It seems to me the fuel delivery is not keeping up with the demand and once it sucks the carb bowls down it starts starving for fuel. I've checked the fuel filter, checked all the carbs (no plugged up jets, inlet needle and seats look good) spark plugs are good, rebuilt the fuel pump. Yesterday at the lake I found the fuel tank vent hose had a bad kink in it so I disconnected it at the tank and it seemed to help some but still wanted to bog down on me at full throttle. Not sure where to look next. A while back I found the hose from the enricher solenoid had cracks at the connection to the solenoid so thought maybe it was sucking air so replaced the hose (not with the OEM hose just used some fuel rated hose from the auto parts store) but that didn't fix it either. I'm wondering about the fuel supply hose from the tank now (it was replaced in 2012) wondering if it might be deteriorating inside from the ethanol in the fuel but not sure. Any ideas? Thanks.

 

[racerone]

Test run with another tank and hose.-----Running a 2 stroke with fuel starvation issues can do big $$$ damage to pistons.----Post actual values of a compression test here.----Motor needs a new water pump about every 3 years.----Has that been done?----Tested the overheat horn if equipped with one ?

 

[jimmbo]

Those engines had not Overheat Indicators, but a Pressure Gauge that would likely be ignored, was an Option

 

[jimmbo]

Is this a Permanent Tank, or a Portable Tank? Either way, pull the Fuel Pickup out and check for blockage, of the Strainer on the end of it

 

[popknot]

Test run with another tank and hose.-----Running a 2 stroke with fuel starvation issues can do big $$$ damage to pistons.----Post actual values of a compression test here.----Motor needs a new water pump about every 3 years.----Has that been done?----Tested the overheat horn if equipped with one ?

Motor was rebuilt in 2012 with all new pistons and has very few hours on it since. I just replaced the water pump impeller. I don't believe there is an overheat horn, the boat didn't come with a temp gauge. The marina that rebuilt it in 2012 replaced the fuel line with the sierra silverado fuel line in 2012. Don't know if that fuel line would deteriorate that soon or not(11 years)

 

[popknot]

Is this a Permanent Tank, or a Portable Tank? Either way, pull the Fuel Pickup out and check for blockage, of the Strainer on the end of it

Its permanent. Checking the strainer sounds like a good idea if I can get to it. I didn't think of it while I was at the lake but I probably should have hit the enricher while it was bogging and see if it picked up Then I would know its a fuel issue.

 

[racerone]

Some of the last production runs did finally use a temperature warning switch.----Easy to look up.----Test run with a portable tank and known good hose.

 

[popknot]

Some of the last production runs did finally use a temperature warning switch.----Easy to look up.----Test run with a portable tank and known good hose.

 

[popknot]

Some of the last production runs did finally use a temperature warning switch.----Easy to look up.----Test run with a portable tank and known good hose.

Will do sounds like the place to start. Thanks.

 

[jimmbo]

Some of the last production runs did finally use a temperature warning switch.----

And only $125(us) Learned something new about the I6 today

 

[jimmbo]

Its permanent. Checking the strainer sounds like a good idea if I can get to it. I didn't think of it while I was at the lake but I probably should have hit the enricher while it was bogging and see if it picked up Then I would know its a fuel issue.

The Enricher gets its fuel from either a Carb Bowl, or from the Fuel Line going to the Carbs. If the Carbs are starved, the enricher will likely be starved too

 

[Chris1956]

Hitting the primer when she bogs may not help, as you seem to have a fuel delivery issue. No fuel for the carbs = no fuel for the primer.

Since you already rebuilt the fuel pump, replace any fuel filters or water separators you find.

I always thought 5/16" ID fuel line diameter was marginal for those IL6 motors. If all else fails, first remove the quick disconnect, if still using it. If that doesn't help, replace the fuel line with a 3/8" ID fuel line.

JMO

 

[popknot]

Do you know how I would get to it?

 

[popknot]

Theres a picture of my fuel line where the quick release attaches.

 

[popknot]

sorry the photos are so big I'm not used to donig things on this imac yet. I think I need new fuel line.

 

[jimmbo]

While your fingernail is fairly sharp, whatever is on the Hose, isn't. If there is some goop in there, it might also be in the fitting that you pulled the hose off of

 

[Texasmark]

You didn't mention an onboard (the engine) fuel filter. Even if it was changed I would replace it with what I see in the last picture. One thing you didn't mention that is an easy try is to squeeze the primer bulb in the fuel line when it wants to bog. If it recovers you have restrictions blocking the line or your fuel pump overhaul needs revisiting....you said they replaced the fuel lines in the engine.....might look them over at the fittings looking for fuel leaks and cracking. On replacing the fuel filter, cut the old one open and report back what you find.

 

[popknot]

While your fingernail is fairly sharp, whatever is on the Hose, isn't. If there is some goop in there, it might also be in the fitting that you pulled the hose off of

I couldn't get a very good picture but the goop inside the line is the lining thats in side the fuel line . It looks like it has a inner plastic lining in the fuel line. When I cut the plugged up part off and pushed the fitting back in the line the inner liner just bunched up inside the line and plugged it up again. It looks to me like the marina put 5/16 line on 3/8 fittings

 

[popknot]

You didn't mention an onboard (the engine) fuel filter. Even if it was changed I would replace it with what I see in the last picture. One thing you didn't mention that is an easy try is to squeeze the primer bulb in the fuel line when it wants to bog. If it recovers you have restrictions blocking the line or your fuel pump overhaul needs revisiting....you said they replaced the fuel lines in the engine.....might look them over at the fittings looking for fuel leaks and cracking. On replacing the fuel filter, cut the old one open and report back what you find.

Should have thought about squeezing the bulb and seeing if that helped. I'll replace the fuel filter and take a look at it. Thanks.

 

[popknot]

I've ordered 5/16 and 3/8 fuel line should be here Thursday. If the 3/8 fits the fittings ok think I'll go with that.