mercury 1150

[bkd13]

I have a 70s model mercury 1150 115hp I had problems with the prop venilating and it was cutting off by itself like you killed the swithc I think the problem with that was the harness not beeing plugged in good it hasn't done it anymore but now my problem is I took it to the lake today with a 3blade 22p prop and and when I got there it was idling good but when I put it in gear it would die so I. Made the fuel screw a littled richer richer and that helped and it ran out the lake fine then while running wot it lost rps and was like it would only go 3/4 throttle and just seemed weak and would not idle. . . I also tried a 21p prop and it still would go wot and still didn't wanna idle or take off. . . Good compression new spark plugs any help would be greatly appreciated thanks

 

[Gomer50]

Re: mercury 1150

Couple of things to check,first make sure your anti syphon valve on your tank is in good shape, tank vent is open so it doesnt create a vacum inside the tank.Take your fuel line off on the side that feeds the carbs (after the fuel pump and crank the motor to see if you have a good stream) if not rebuild fuel pump.On some carbs depending on the year have a dome on the carb where the fuel comes into the carb, inside the dome is a fuel filter maybe clogged?? On later 70's models on the carbs where the fuel enters the carb behind the brass barb is a small screen which can be clogged as well. And last but not least dirty carbs period sticky inlet needles, damaged float, clogged jets.

 

[bkd13]

Re: mercury 1150

I took the line off the carbs and one fuel pump had a steady stream the other had nothing so I ordered the kits also my primer bulb is a little hard to blow through should it be

 

[Chris1956]

Re: mercury 1150

A 21P or larger prop will only work on that motor with a light boat. What kind of boat are you running?

 

[bkd13]

Re: mercury 1150

Its on a 17 foot allison craft very light boat

 

[Chris1956]

Re: mercury 1150

Check for spark leaking out of the plug wires and arcing to ground. Check for plug fouling. Check max spark advance and idle pickup timing.

 

[bkd13]

Re: mercury 1150

Check for spark leaking out of the plug wires and arcing to ground. Check for plug fouling. Check max spark advance and idle pickup timing.

How do is check max sprak timing advance and idle pickup timing?

 

[Chris1956]

Re: mercury 1150

You should get a service manual, as it sounds like you will need it. An OEM one is best. Idle pickup timing is when the carbs are just about to open. Max spark advance is at 7/8 throttle or so. Despite what the service manual says, remove the spark plugs from cylinder 2-6, stick them into their spark plug wires, tape them together and ground all their bases to the block.

Now set the throttle until the carbs are just about to open and check timing with a timing light. Most of the Thunderbolt distributor ign motors need 4-6* BTDC as idle pickup timing. You adjust the collar on the distributor and the throttle to achieve it. Now advance the throttle full and check max spark advance. use the set screw above the distributor to set it to 21*BTDC.

 

[bkd13]

Re: mercury 1150

is the timing something that could have changed by itself just cruising the lake because it did fine when i first got to the lake?

 

[Chris1956]

Re: mercury 1150

No, the timing would not change by itself, unless you removed the timing belt or adjusted the distributor in some way. Of course, it could have been all messed up by the PO.