mercury 115 thunbolt stack 6 not ruin very strong

[17.5cobra]

Hey I have a merc 115 and it runnin kinda funny not sure had the carbs off and cleaned them the motor sat for a year or so they were set up in a tank and the guy was merc. mech. but the top four plugs look oily and the bottom two are fuel washed the mech. said check the leads and see if they had continuity they do if they were firing would they be oily too runin it 50:1 it has spark couldit just be weak not sure anyone help.

 

[daveswaves]

Re: mercury 115 thunbolt stack 6 not ruin very strong

Hey I have a merc 115 and it runnin kinda funny not sure had the carbs off and cleaned them the motor sat for a year or so they were set up in a tank and the guy was merc. mech. but the top four plugs look oily and the bottom two are fuel washed the mech. said check the leads and see if they had continuity they do if they were firing would they be oily too runin it 50:1 it has spark couldit just be weak not sure anyone help.

Cobra, welcome to I boats, before anyone can help you you must give additional information. What year is the motor or if you don,t know the year give us the serial number. It sounds like an inline 6. Kinda funny does not describe anything to the community, we need descriptive information, as much as you can give. If you are not sure of the technical terms then tell us what it sounds like (eg, farts, sneezes, clanks, whirs, hickups, squeeks...you get the idea.)

 

[17.5cobra]

Re: mercury 115 thunbolt stack 6 not ruin very strongmore info request

Re: mercury 115 thunbolt stack 6 not ruin very strongmore info request

Hey thanks for getting back to me.The serial # is 3274407 I think it is about a 79.The mechanic who tuned the carbs said it was running fine in the tank but when I got out on the lake it seemed to be missing some top end power. It would power up to a point but as soon as i got on to plain it seemed to lose all its power somtimes it would just lose everything and die but if you put it back into nutural it would start right back up.Other times it would seem to surge like it was the power was cuting in and out.I have spent alot of time working on cars and all I can capare it to is like if you where driving your car and you took your foot on and off the gas really quickly.

 

[daveswaves]

Re: mercury 115 thunbolt stack 6 not ruin very strongmore info request

Re: mercury 115 thunbolt stack 6 not ruin very strongmore info request

Hey thanks for getting back to me.The serial # is 3274407 I think it is about a 79.The mechanic who tuned the carbs said it was running fine in the tank but when I got out on the lake it seemed to be missing some top end power. It would power up to a point but as soon as i got on to plain it seemed to lose all its power somtimes it would just lose everything and die but if you put it back into nutural it would start right back up.Other times it would seem to surge like it was the power was cuting in and out.I have spent alot of time working on cars and all I can capare it to is like if you where driving your car and you took your foot on and off the gas really quickly.

Ok, great reply, this will hopefully be an easy fix. The problem you are describing is caused by the idle circuit being set too lean. The engine "falls flat on its face" when placed under load. This is exactly what happens when you are attempting to come up on plane, you are at your highest load and there is simply not enough fuel to sustain the work you are trying to do. To fix the problem you need to rich en your low speed circuit. Back the idle mix screw on each carb out ( counter clockwise) 1/4 turn and then try your launch again. If it still falls flat or stumbles back the top carb out 1/4 turn and try again. If it still falls flat back the middle carb out 1/4 and try again. If it still falls flat back out the bottom carb 1/4 turn and go again. At some point in this process you will hit the magic spot.
When you are all done this process your idle speed will likely need to be adjusted. It should idle at around 800 rpm in neutral and 650 in gear. Adjust the idle speed with the adjustments on the advance plate to the right of the carbs. Do not adjust idle with the carbs.
Generally speaking the inline merc CAN NOT be adjusted in a test tank and ANY mechanic that tells you "it ran fine in the tank" is simply not familiar with the mercury Inline 6 engine. You can get it running in the tank, you have to tune it on the water.

 

[17.5cobra]

Re: mercury 115 thunbolt stack 6 not ruin very strong

Hey thanks that sounds easy enough I'll give it a try and see how it works.This is a great site it's good too know there is guys like yourself with good advise look for my response on how it went THANKS.....

 

[17.5cobra]

Re: mercury 115 thunbolt stack 6 not ruin very strong

Well I tryied what was sugested but still the same problem.Is it possible that when i re did the carbs I got a float stuck or out of ajustment.I know I had a similar problem with my motorbike and it was the float was out of ajustment. Anymore sugestions anyone.