Early seventies Mercury 1250 Wont Start

[rriley]

I just got an early seventies boat with a Mercury 1250 on it and it started when I got it by using throttle body cleaner in the cylinders but it was really hard to get started. Once it started it sounded great though. Once I got it home I have had a hell of a time trying to get it started. I replaced the spark plugs to no avail and am wondering what else easy I can do before I take it in to a shop. There is a shop near by that said they can most likely get it running with a tune up for around $200. I am somewhat mechanically inclined but I have only had one 2-stroke and I did minimal work on it. Anything helps.

Thank you,

 

[merc850]

Re: Early seventies Mercury 1250 Wont Start

Great looking rig that setup looks brand new! First check all the
wiring for broken or disintegration inside the motor, replace it with a new harness if the next tests are good. You should: do a compression check - all plugs out and grounded (wire the bases together and connect to block) and fuel line connected, see if a spark will jump 7/16" gap, check that the choke is closing when you press button, to test carbs quickly tilt engine up on trailer locks and pump primer ball 'til gas runs out of carbs this is also a way to see if water is in gas. Fresh gas and oil 50:1. When you get it running replace water pump impeller before using.
Keep posting 'cause that boat is super classic.

 

[j_martin]

Re: Early seventies Mercury 1250 Wont Start

And don't spray anything into it but 50:1 fuel and oil. Carb cleaner, etc will both strip the lube and pre-ignite, harming the engine.

 

[merc850]

Re: Early seventies Mercury 1250 Wont Start

And don't spray anything into it but 50:1 fuel and oil. Carb cleaner, etc will both strip the lube and pre-ignite, harming the engine.

Isn't that a wild looking rig!!
[
Can't help admiring the condition of the boat/motor, if I lived near you I'd work on it for nothing, as it is you should get a manual to help you.

 

[Maxz695]

Re: Early seventies Mercury 1250 Wont Start

It is Pretty!

 

[79Merc80]

Re: Early seventies Mercury 1250 Wont Start

It is pretty. But it's either a 68 or 69. Those were the only 2 years the 1250 was made. I grew up skiing behind a 1250. Also the only Mercury that retarded the timing from about 3/4 throttle to WOT.

Craig

 

[Chris1956]

Re: Early seventies Mercury 1250 Wont Start

That boat looks like my Avenger. I had a Merc 1500 on it until it blew and I put a Merc 135HPV6 on it. It cooks.

As was said, if the compression is good on that Merc, the rest is fixable. You need to choke the daylights out of the motor when cold starting. After it has been run, it should start in 1 sec, w/o choke, for the rest of the day.

Let us know if the choke plates (2 only) close, and what the compression numbers are.

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

Thanks guys. I got it for 1500 with two trailers, so I figured it was a strong deal. Ill check today but it doesnt seem like the choke button does anything. Is that the same thing as the manual choke thats on the engine? Also, the guy I bought it from didn't have it for long but is a mechanic at some dealership and did a great job of replacing the bad wiring on it. Here are some pictures of the engine. Sorry they are from a phone.

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

Oh, and if it helps the year question, it does say thunderbolt ignition on the front of the engine.

 

[Chris1956]

Re: Early seventies Mercury 1250 Wont Start

Looks like it is in great shape, at least in appearance. There should be a cold start lever on the MerControl. There also should be a choke button on the MerControl. To cold start her, lift cold start lever all the way. Now hold down choke botton (you should hear click as choke plates close), and crank motor with key until she starts.

There should be a manual choke button on top cowling support. You can pull this directly upward to manually close shutters and choke motor

 

[Gomer50]

Re: Early seventies Mercury 1250 Wont Start

That is a fine looking piece of Mercury History.

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

I have been using the cold start as well as the manual choke it to no avail. Im just stumped on what to do because of my lack of knowledge on two-strokes.

 

[Mi duckdown]

Re: Early seventies Mercury 1250 Wont Start

rriley. If ihad that motor, I WOULD have/FIND an OEM MERCURY SERVICE/REPAIR manual for That Motor. Got 2 and I would not give them up for anything.
You can read them in your easy chair,and then take them to the garage.
Seen them on ebay.
SERIAL NUMBER IS A MUST

 

[Chris1956]

Re: Early seventies Mercury 1250 Wont Start

Did you ever take that compression test, and post the numbers? If it has low compression, it will be a hard starter.

OK, lets pretend the compression is OK. Install flusher device and turn water on. Squeeze the fuel primer bulb hard. You are attempting to flood the carbs a bit. Now cold start lever all the way up. Push choke button. Do you hear click? If not, remove wrap cowl and top cowl. Now pull up on manual choke knob and see carb shutters close. Now crank motor with ign key until she starts. feather choke until motor warms. If electric choke did not work, get it fixed as you will need it.

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

Alright, finally got the compression test kit. I just did it and got 95s for all of them except one which was about 82. The numbers seem lower than they should be but I'm not sure.

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

I'm sure this is somewhere on another thread but I was having a hard time finding an answer. Does anyone know if these ^numbers^ for compression are ok?

 

[Chris1956]

Re: Early seventies Mercury 1250 Wont Start

There is no spec for compression numbers. The spec is for how even the compression is. I suspect your gauge is inaccurate, however, they are usually reliable, so your numbers are pretty even, and therefore acceptable.

I would bet an accurate gauge will show them as 120 for 5 of them and 110 for the low cylinder. I think that is fine and it's an old motor, so let's run it....

 

[rriley]

Re: Early seventies Mercury 1250 Wont Start

Cool, because I have been worried that it will need to be rebuilt. Is it possible it needs new points?

 

[merc850]

Re: Early seventies Mercury 1250 Wont Start

No they were ahead by 2 years

 

[maagee79]

Re: Early seventies Mercury 1250 Wont Start

this will help with the year of the motor if still wandering. http://stores.ebay.com/Outboardnuts/Mercury-Year-Lookup.html