Starting to work on latest project - Merc 1150 - Help with wires needed

[WA-Newb]

I have taken a break on my Johnson and moved that boat over to my parents house so I can try to assess my latest purchase which is a 1960 Glasspar Seafair Sedan..it came with a Mercury 1150 Thunderbolt which was said to "run good"...but I will believe that one when I see it...lol I am mostly interested in getting the boat fixed up but have to decide if this motor is a keeper or not.

Before I spend any money on this I would like to check compression (have already soaked pistons and will do again before trying to turn it over) but my main problem is the notorious wire harness which will basically crumble away when touched and has already in many spots.

I cannot afford to spend money on a new internal harness so I was hoping one of you experts could tell me what wires I would need to fix / hard wire / or whatever in order to crank this thing over for the compression test..I read on another thread I could jump the starter solenoid so I didn't damage any electrical components when turning it over.

My knowledge is very limited on outboards and especially Mercury..I can usually research and figure things out but any help on this matter is greatly appreciated.

Will it be possible to actually rebuild the internal harness even if only for a temporary testing phase? Or would it be better to cut both connections of the harness and hard wire the ends together?

Also, will the harness from the controls to the motor be all brittle and falling apart as well or is the cause from the heat of the motor mostly?

Thank you.

 

[calvinator]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

Jump the starter motor (youtube for examples) and it will turn over to perform the compression test.
Make sure the throttle is fully open to get accurate compression PSI.
I've seen 130, 140, 150 PSI on these motors.
According to the service manual, below 80 is rebuild.

If you have good compression, I would spend the $$ for the wiring harness and get it done right. These motors in top shape sell well!

Mercury Outboard Wiring diagrams -- Mastertech Marin
has all the wiring info you need too.


And your brittle control cables, well, they age out too. You motor is probably from the 1960s or 1970s !

 

[WA-Newb]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

So can I jump the starter motor even with all of the wires disconnected / gone? or do a couple of them need to be replaced first?
All wires coming out of the harness are pretty much non existent right now, except for maybe the ground and if there is another thick one like the starter cable.
Thanks

 

[DirtyOldBoat]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

Just jump positive and negative to the starter directly. That's it, no other wires.

As for rebuilding it, you don't have to spend a ton of money on a new harness. I rewired my 1500 completely without one, the only real difference is there is no quick disconnect on the outside of the motor. I don't take my motor off the boat, so this isn't an issue. I just used bulk wire in a bunch of different colors and soldered on ring terminals with a little bit of heat shrink tubing. Looks very professional.

Definitely replace all the old wires, they are nothing but trouble.

 

[WA-Newb]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

Ok thank you..I was hoping that would be the case

If I decide it's a keeper or worth something then I may end up spending some money on it.
I am going to try and do a compression test today while I have day off.

Thank you.

 

[WA-Newb]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

I am watching a youtube video right now on this motor but can't tell if the front cage (that's what he called it) needs to come off in order to get the top cowling off...or if I can just unbolt the top cowling and remove it so I can get to the top plug?

Also there sure isn't much room on the bottom plug either..hoping I can get my compression tester screwed into that one with no problems.

Hope that makes sense...I have not finished my coffee yet this morning and usually try to stay away from cyber verbiage until I am caffeinated...lol

 

[WA-Newb]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

Well I am not having any luck getting the starter to turn over...now it could be that all four of my batteries are just not charging so am going to go get my new battery and try that.

In the meantime I am wondering if I should have the throttle wide open and IN GEAR when jumping the starter for the compression test? I have read that throttle should be open so figured I would just use the throttle lever but maybe this is not the proper way to do it?

Also..I just found a part that was given to me by the PO and he didn't remember what it was...looking at the wire diagram I see it listed as a "Mercury Switch". Can someone tell me what this is and if it's needed (or why he may have had it removed in the first place).

Thank you.

 

[Chris1956]

Re: Starting to work on latest project - Merc 1150 - Help with wires needed

No need to put the motor in gear or open throttle for compression test. Simply crank it until gauge stops rising. The Mercury switch grounds the ign if the motor is tilted up or is kicked up while operating. It is optional to use or not use it, IMHO.

You want the compression to be even on all cylinders. The top cowl is removed with a flip lever in the front of it. There should be no need to remove the cowling support. I presume you have removed the wrap cowl. Cylinder 6 is a challenge to get the compression guage onto. I use a 90* elbow to get to it.