1976 Merc. 115 , 1150 model

timjsowards · Apr 23, 2007

Ok , so heres the deal Im having what seems to be a throttle issue, I can be running fine at a good speed then just dies out of nowhere, it will usually restart right away sometimes it may take a few cranks, then again at times ill be running fine and the idle just drops to almost nothing and it will stay there no matter where the throttle is at , I dont know alot about outboards but have been told due to the age none of my local service shops will work on it so i guess its up to me to figure it out, I am very mechanically inclined and know alot about vehicle engines and can tear down and rebuild about anything with 4 wheels but an outboard is completely different, i also have a issue with my tilt motor as of yesterday it will not go down, it is stuck in the up position, it does run , i push the buttons and i hear the motor in both up and down but no movement, Please help me its fishing season and all i want is to be on the water. Thanks

hammyloz · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

in respect of your tilt trim have you checked the catches for towing are not in place silly question i know but hey you never know
the throttle sounds like dirty carbs but i`m sure the experts will be along for that one

timjsowards · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

Yea, that was the first thing i did was check to make sure I flipped them down, i was thinking maybe low on hyd oil but i dont know how to fill it, the pump is inside the compartment beneath the transome and isnt the easiest to get to and i have no idea where the oil would even go in at , thanks

Chris1956 · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

Tim, The fill for the T/T pump is the non-painted aluminum straight slot screw on the top right of the pump. Fill with 5W-30 motor oil. Make sure the reverse lock screw (Knurled knob on pump base) is engaged.

The running issue you have may be due to a weak fuel pump, restriction of fuel supply or bad fuel primer bulb. Have someone pump the bulb while you are running at high throttle opening and see if it is better. The motors need plenty of fuel at WOT, and the pumps can barely keep up. Another way you can check it if you are alone is to pump the primer bulb when it stalls out. If it takes more than one pump to get hard, you have a fuel pump issue, bad primer bulb, fuel tank vent clogged or the fuel line is too narrow. Ideally you should have a 3/8" fuel line.

timjsowards · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

Thanks for your help. I do have the 3/8 line and the screw for the vent on the gas tank is open about half way or so, I ordered the manual from Mercury but it wont be here for at least another week or so and I’m just really wanting to do some fishing and get on the water, I will have to check the prime bulb, I planned on replacing it anyway so I might as well do that, I’ve also looked into cleaning the carbs but as I said I’ve never worked on an outboard before so its all new to me, I really appreciate the advice though thanks

hammyloz · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

i tell you Tim doing the carbs is a doddle
thanks to iboats an all the experienced people on here i managed to strip an rebuild my carbs an other silly thing to keep the tower of power running sweeeeeet

Plainsman · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

Just a note on filling the tilt/trim. Disconnect the power for the T/T motor at the battery. It may spark on ya if you touch the connections with the screwdriver, don't ask how I know.

There is also a vent screw on top of the T/T motor, loosen that, it will fill easier as the air has a place to go.

timjsowards · Apr 23, 2007

Re: 1976 Merc. 115 , 1150 model

Thanks everyone for your help, i did put oil in the t/t motor still no movement, no leaks, all buttons work and i can still hear it running, unfourtunatly i had to order the carb gasket kits to take the carbs off to clean out and that will be at least 3 or 4 days, ill keep you posted on that issue, but i still need to get this thing to drop somehow, can you remove the cylinders and let it down that way? I didnt know if you could or not but if the motors running then what else could it be ? Thanks

Chris1956 · Apr 24, 2007

Re: 1976 Merc. 115 , 1150 model

Tim, You might open the hydraulic lines at the pump to see if you have trapped air. The pump is supposed to be self bleeding, but who knows. if you loosen the nuts on the lines (large lines are down), oil should be forced out when you run the motor.

Plainsman · Apr 24, 2007

Re: 1976 Merc. 115 , 1150 model

Which way is the knob turned on the pump? It should be screwed out to use the hydraulics and in for manual release.

timjsowards · Apr 24, 2007

Re: 1976 Merc. 115 , 1150 model

Right now its turned all the way to the left which the manual says is the unlock position and ive tried it in both positions, i would think that even if one cylinder blew out it would still go down, may not come back up but at least go down, pump and cylinders are full of oil , and motor runs. So im at a point where i have no idea. thanks

Plainsman · Apr 24, 2007

Re: 1976 Merc. 115 , 1150 model

Here's stupid question, and not to offend you, but you do have the tilt lock off, right? The little arm that pivots on the left side of the engine.

Chris1956 · Apr 25, 2007

Re: 1976 Merc. 115 , 1150 model

Tim, I recommend you open one of the hydraulic lines and let some oil out to allow the motor to go down. Now make sure the reverse lock is engaged, and try the trim system.

CharlieB · Apr 26, 2007

Re: 1976 Merc. 115 , 1150 model

Diagnost the trim system
First get your hands on a test light
Verify that the pump is running the correct direction, not running 'up' when you hit the down button, just to be sure that you don't have a strange wiring problem.

Second, test the 'double action' hydralic cylinders by removing the 'up' line and hit the down switch. Test one cylinder at a time.
Low pressure oil should come out, but here is the catch, if the piston seal is bad the cylinder will NOT go down, the pressure will bleak past the piston and build on the 'UP' side. So a bad cylinder and the drive will only go 'UP'.
More surface for pressure to work on than on the rod side of the piston, more force.

Chris1956 · Apr 27, 2007

Re: 1976 Merc. 115 , 1150 model

Charlie, I do not agree with your statement. I had a piston seal go bad in the PTT system. The motor would slowly drop down. That's how I found it.

Scaaty · Apr 27, 2007

Re: 1976 Merc. 115 , 1150 model

Ya know you have to keep the pump vent screw loose, right? doubt thats the problem though..might want make sure any trim limit switches on the OK side of good..
Turning the reverse lock screw in should have you whipping that puppy up and down by hand
Is the motor spinning free, or is it under pressure (like in full up or down..ya can tell the diff)

1976 Merc. 115 , 1150 model

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