1973 Mercury 115 2 stroke engine questions

[Infinite Monkeys]

Hi,
I bought a 1973 complete boat with the 115 HP engine and trailer for $500. No idea if the engine is good, but hope so. I was told it's good. The key is missing so I can't really test it right now. I want to remove the engine and tilt/trim to put on my bass boat.
First question is:
The tilt/trim does not work, I can hear the pump running, but motor does not move. I assume it needs fluid. I'll address the leaks later.
What fluid does this take, ATF or 10-30

Thanks again.

 

[racerone]

Some old time Mercury dealer might have a key, on hand.------Inspect wiring on motor and inside control box.-----Key switch might have a number on it.----Is there a knob under the pump reservoir ?---Do a spark check as well.---Do a compression test before spending any beer tokens.----If motor is a runner it needs a new water pump impeller.

 

[Infinite Monkeys]

I'll start work on it in a couple days. The key cylinder is destroyed, looks like a screw driver was used to turn the switch. I tried that and got nothing at the motor. I haven't checked the switch wiring.
I'll replace with a new switch.
I can jump the solenoid and get the starter to spin. So at least that's not Iocked up. But I think it is just the starter spinning not the engine. Not sure on that.
I'll start with a compression check. Likely will need to fix the switch to turn over the engine. Think there's no power to the control box.
Still would like to test the tilt, trim.
There are leaks from the pump. So its likely empty, so what fluid should I use? It has the remote mounted pump.
I'll go through it eventually and do all the maintenance.
Thanks

 

[racerone]

A number SAE 30 oil was used in those early units.-----Good enuff for a test.

 

[Chris1956]

You can easily jumper the ign on that motor. However, the ign components are real expensive, so one does not want to mess it up.

As was said, Merc Dealers had maybe 12 keys for all the OB motors. If you can drag the boat to a dealer, a key could be had in a minute or two, unless the key cylinder is wrecked. If you cannot get an original key, post back and I can advise on how to jumper.

The ign keyswitches were usually soldered in. Hopefully you have a powerful soldering iron and some expertise on hot joints. If you have a MerControl, make sure to get an OEM Keyswitch, as aftermarket may not fit the MerControl.

 

[1960 Starflite]

Might as well drop the lower unit since you're going to be cranking that thing. If compression is ok and it then fires, head to water pump. I have 2 1960's Mercs and the wiring is fine but the 1975 wiring was toast.

 

[Infinite Monkeys]

Well the key is toast. I did a compression check on 5 of the cylinders, bottom one is too hard to get to. The range is from about 90 to 98. That's on a cold, dry engine that's been sitting for years.
Is that within an acceptable range?
I did not check for spark because of the key and I'll use the key in my other boat anyway. Mainly need some thoughts on the compression.
I'll work on the tilt/trim, fuel lines, impeller, prop seal, timing, etc. when it's out.
Thanks again.

 

[Infinite Monkeys]

You can easily jumper the ign on that motor. However, the ign components are real expensive, so one does not want to mess it up.

As was said, Merc Dealers had maybe 12 keys for all the OB motors. If you can drag the boat to a dealer, a key could be had in a minute or two, unless the key cylinder is wrecked. If you cannot get an original key, post back and I can advise on how to jumper.

The ign keyswitches were usually soldered in. Hopefully you have a powerful soldering iron and some expertise on hot joints. If you have a MerControl, make sure to get an OEM Keyswitch, as aftermarket may not fit the MerControl.

I read this after jumping the solenoid for the compression check. Hopefully I didn't mess anything up.
Thanks.

 

[richw46]

My 1995 115 Merc uses ATF in the trim-tilt, not motor oil. It's a hydraulic pump so it needs hydraulic fluid. You should see if you can't find an owner's manual for your motor. Your motor may be different, better check with a local shop. Post a picture of the pump



If you put fluid in it and it still won't raise the motor then your seals are probably worn or missing. I made a video when I rebuilt my trim-tilt, maybe it will help.

 

[Infinite Monkeys]

I think at this point I'm going to try and start it and see how it runs. I'll hotwire the ignition and choke wires and give it a go.
Seems the ignition switch has power in, ignition on, ground and crank. And the choke has power in from switch, power out and ground. Which ones are which?
I'll trace them back to the engine and battery, but would like to get an idea ahead of time.
Thanks again

 

[Chris1956]

The switchbox needs power on the red and adjacent white wires to provide spark. Red is always hot and the white is given power when the ign key is on or start.

The wires on the distributor are often bad. You might check them.

 

[Infinite Monkeys]

Got the ignition switch wired and I have spark. I tried to put fuel in it but the lines are leaking really badly, so I need to address that first. I need to get the lower engine cover off to get to the lower fuel pump.
Does the lower unit need to come off before that can happen?

Thanks.

 

[Infinite Monkeys]

And it runs. Runs really well too. It was leaking from the main line coming into the top pump, so I put in a threaded, barbed fitting and that works for now.
The Chrysler I'm working on in the other thread smokes like a chimney compared to this. This engine is now going to come off the boat and go on a stand.
Still would like to know how to remove the lower cover.
Thanks all for the help!

 

[Chris1956]

The lower cowl only comes off it you pull the powerhead. Buy some gasket sets for the carbs and some inlet needles and seats and floats... Say $40, clean the carbs, including the idle restrictor and idle passages.

 

[Chris1956]

That motor is a really good one. It will really make it happen with a fast/light boat. It is OK with a heavier boat as well

BTW, SAE 5W-30 motor oil was used in those PTT units.. I would advise that you see what you have and continue using it.

 

[Infinite Monkeys]

I found the impeller kit, looking for the carb kits now. It's serial number is 3651931, if someone has quick access to the part numbers for them.
Thanks

 

[jimmbo]

My 1995 115 Merc uses ATF in the trim-tilt, not motor oil. It's a hydraulic pump so it needs hydraulic fluid. You should see if you can't find an owner's manual for your motor. Your motor may be different, better check with a local shop. Post a picture of the pump

View attachment 380200

If you put fluid in it and it still won't raise the motor then your seals are probably worn or missing. I made a video when I rebuilt my trim-tilt, maybe it will help.

Yours is a completely different Tilt-Trim System than what was used in 1973, and you are correct to use ATF in it. However the previous design used SAE 20 as the fluid.

 

[richw46]

Yes, I saw your post, fascinating. I wasn't aware of that. Apparently it's been in use for a long time.

 

[BulletGenius]

The lower cowl only comes off it you pull the powerhead. Buy some gasket sets for the carbs and some inlet needles and seats and floats... Say $40, clean the carbs, including the idle restrictor and idle passages.

I am looking for these items at the moment too. Carbs seem to be VERY stuck to the block. Im affraid to take them off.

The only problem with mine (73 115hp) is WOT only lasts a few seconds and makes me retard thottle or have someone pump the ball while running to get enough fuel to maintain WOT.

 

[BulletGenius]

Infinate Monkeys, mine got rebuilt in 2014. Ill check the notes for what the mechanic said to use for the trim in the morning. Im thinking ATF. Also, it is prone to sticking so, if it does, and you dont want to overhaul it "tap the top to unstick the brushes". Works when it has for me.

I am currently working on mine, putting new fuel line in, and trying to find out what is going on in the carbs without taking them off.

The lower cowel can be lowered a few inches to help reach cylinder #6 if you unbolt the front two 1/2" bolts on the bottom of the front plate, and four in the back plate. I would take off the fuel pump first though because it will be held up by the fuel lines mostly. A sneaky 5/16ths on the back of the fuel pump is a pain to get in and out in my experience so I start with that one.

I rewired mine four years ago and noticed somthing different from yours... that red wire dosent seem to exist on mine. I have always had an empty terminal on the red area. Can you show where that leads?

It would be nice to bounce some engine comparisons at eachother, if you are interested let me know.
P.s. Mine is attached to a Glastron/Carlson CV-16 That I am planning on selling as soon as this is figured out. I plan on running it tomorrow.

Best of luck!