1969 Merc 500 Thunderbolt (50HP) Hot-Wire/bypass key switch?

DropKick1087

Recruit
Joined
Nov 8, 2009
Messages
2
Hello everyone! I am new to this forum as well as boats in general. I have general knowledge of motors and such but I do have a question. I am looking at buying a 1969 Merc 500 Thunderbolt. The guy didnt know the year so I had him give me the numbers from the motor. The only problem is, I have not seen Thunderbolt as a 1969 motor, yet I see it for 1970. But that is really besides the point to this posting....

I am wanting to see it run before I buy it, like most other people would want to see as well. The only problem is, the key switch posts are corroded and will not fire up, it will just turn over, at the end of this post I will ask a series of questions so you do not have to search through my drawn out post =P.

I would be getting this motor for $250 if I decide to buy it. And now for the questions.....


1) Is there a way to "hot-wire" the motor to see it run? I looked at the wiring diagrams of the motor and by the key switch it is labeled "Key Switch" with "OFF" = D-E
"RUN" = A-F
"START" = A-F-B

The question is... Do I jump the wires A-F-B to start it with the ignition? I am familiar with bypassing wires and all, but it's for appliance switches, lol. If some one knows the procedures as to doing this, I would greatly appreciate it.

2) If there is not way to bypass the switch... Does this motor have a way to pull start it? Ive read other forums talking about a lot of the smaller motors have a nylon cord near the flywheel.

3) The guy said it has good compression. Can you tell how the compression is without it running?

4) Any other input would be great. Tips for checking things out with boat motors, etc. I know some visual signs to look for, gaskets that are not painted is more than likely a sign that it has been torn apart, etc.

I would like to apologize if I had posted any "stupid" questions. But I feel that is the only way to learn about this motor as I've spent an hour looking for more details. The hot-wire questions wasn't exactly answered on any other page/forum, that is why I am here. I am suppose to go look at it with my uncle tomorrow afternoon, he knows a lot more about boat motors than I do as he is a certified mechanic. So I wouldn't be going to look at it blind. I am pretty sure the diagram that I have pulled up on google is in fact the one for the 1969 merc 500, but with the Thunderbolt model, I am not sure. If anyone has a link or can send me a diagram that they can draw up would be great. Thank you for your time.

Dropkick
 
Last edited:

Fuzzytbay

Chief Petty Officer
Joined
Jun 6, 2008
Messages
557
Re: 1969 Merc 500 Thunderbolt (50HP) Hot-Wire/bypass key switch?

Hello everyone! I am new to this forum as well as boats in general. I have general knowledge of motors and such but I do have a question. I am looking at buying a 1969 Merc 500 Thunderbolt. The guy didnt know the year so I had him give me the numbers from the motor. The only problem is, I have not seen Thunderbolt as a 1969 motor, yet I see it for 1970. But that is really besides the point to this posting....

I am wanting to see it run before I buy it, like most other people would want to see as well. The only problem is, the key switch posts are corroded and will not fire up, it will just turn over, at the end of this post I will ask a series of questions so you do not have to search through my drawn out post =P.

I would be getting this motor for $250 if I decide to buy it. And now for the questions.....


1) Is there a way to "hot-wire" the motor to see it run? I looked at the wiring diagrams of the motor and by the key switch it is labeled "Key Switch" with "OFF" = D-E
"RUN" = A-F
"START" = A-F-B

Here is a link for the ignition switch diagrams for that year
http://www.maxrules.com/oldmercs/Wiring/1966ona/IgnSw.gif

The question is... Do I jump the wires A-F-B to start it with the ignition? I am familiar with bypassing wires and all, but it's for appliance switches, lol. If some one knows the procedures as to doing this, I would greatly appreciate it].

First off you have to identify which ignition you have. Use the above link and find it. Then you can figure out which wires to connect to which in order to
"hot wire" the engine to test it.

2) If there is not way to bypass the switch... Does this motor have a way to pull start it? Ive read other forums talking about a lot of the smaller motors have a nylon cord near the flywheel.

If you bypass the switch, you can still use the starter motor, by momentarly energizing the solinoid wire to engare the starter. This can be seen in the above link as well.

3) The guy said it has good compression. Can you tell how the compression is without it running?.

You can't check compression with an engine running. You pull the spark plugs, and use a compression tester.

4) Any other input would be great. Tips for checking things out with boat motors, etc. I know some visual signs to look for, gaskets that are not painted is more than likely a sign that it has been torn apart, etc. ?.

http://forums.iboats.com/showthread.php?t=188767
http://forums.iboats.com/showthread.php?t=158086

Read these posts, they should help you out.
 

DropKick1087

Recruit
Joined
Nov 8, 2009
Messages
2
Re: 1969 Merc 500 Thunderbolt (50HP) Hot-Wire/bypass key switch?

Thank you very much sir. That was the info I was looking for.
 
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