3 cyl 65hp Merc wiring cable problem & no serial

[trimjim007]

I just bought a boat with a 3 cyl. 65hp Mercury Thunderbolt and I cannot find a serial number anywhere.

My problem is that it came w/o controls. I bought a standard Merc. control box and the wiring harness has 7 holes (connections) at the end (part that goes to the engine).

But there isn't any place to connect to the engine? There isn't any male connecter anywhere on the engine. And no holes through the cowling.

I think the 7 wires should be wired direct. Can anyone tell me if that is what I should do???

I cannot see where the wires go into the engine. except in the same hole as the shift and throttle controls.

There just isn't any other hole anywhere on the engine?

Please help!

 

[Mike722]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

It is possible that the other half (engine side of harness) was taken off with the old controls. If the person who you bought the boat from took off the old controls, I would ask them about it.

If not, you need to get a wiring diagram to see how it was wired, but you are going to have to find a serial number or someone that can look at it and tell the year, etc.

My serial number is on the transom mount on the right.

Hope this helps or maybe someone else know more about the Thunderbolt.

Mike

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

I looked on the transom mount for the serial number. It wasn't there? I looked inside on the powerhead for a little round welch plug but didn't find that either. I've had other Mercurys but this engine is a mystery to me.

Can anyone offer any advise. I think this is going to have to come from someone really knowledgeable or another 3 cycle thunderbolt 65 hp owner.

Thanks.

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

I have another question: Can the throttle and shift cables be shortened or do I have to buy some the right length?

 

[ricksrster]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

for the serial number look on the top of the part where the tilt swivels or on the block. Does your motor have a distributor?

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

If the engine is a split cowl that hinges open the plug is inside the cowl right next to the place that the shift and throttle cables fasten to the engine it is not round like most merc plugs and is held on the engine with a couple of screws. No you can't shorten cables by cutting them in mostt cases they can be coiled inside the hull as long as they are not coiled to tight that causes them to work hard

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Thanks Laddies!

I thought that that was the case. Unfortunately that part is missing and probably very hard to find.

But I'm anxious to get this in the water, So I went ahead and ran the wire cable through that hole and wired everything direct. If I can find that part later, I will do it correctly.

White to coil
Yellow to celenoid
gray to choke selenoid
red to celenoid
black to ground (at starter)

Since you seem to know alot about this I'd like to ask about the two wires that were left over.

An orange wire that is supposed to go to a mercury switch and a brown wire that is supposed to go to the rectifier.

I could not find a mercury switch anywhere? Do you know what the mercury switch controlled?

And the rectifier doesn't look like another wire was ever attached to it? So I didn't. Do you know whether I need to hook the brown wire to the rectifier? If so which post? What is it for?

I know that a rectifier takes alternating current and converts it to D.C. But for what? and do I need it?

Anybody?


Thanks,
Jim

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Jim, before I can anwser that look on the wiring harness plug and see if there is a 5 digit number that would help and let me know if the engine has a distibuter. The rectifier converts the AC to DC to charge the battery. The mercury switch is a kill switch if the engine is kicked up wilh at high speed it kills the power to keep the engine from slamming down on the transom at full power or just overreving as damaging it's self

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Thanks Laddies,

You are very knowledgable, you must be or have been a dealer. Thank you for your help.

Yes! my engine has a split cowl and if you know where I can gfet the engine side of the plug, I'd appreciate it.

Yes! it has a distributer and coil. The number on the wiring harness from the control box is 45876. I know this is the wrong wiring harness but it should work shouldn't it?

The brown wire is supposed to go to the rectifier according to a wiring schematic I found. But then again since I don't know the year (no serial number found yet) the schematic may not be correct. Especially since I cannot find a micro switch.

I need to know about that brown wire, the orange wire, and if there are any other wires needing to be connected somewhere.

It wouldn't kick over this morning when I tried it. The starter kicked over fine last nite with the hot wire from the battery direct to it so I know the starter is good. It makes a little sound thats all. I put the battery on the charger last nite but still nothing this morning? I suspect that either I do not have the celenioid hooked up correctly or it is bad??? Most likely bad. Is there a way tio test it?

Thank you for your help. I really appreciate it.

Jim

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial


Good news! I found the serial number, It's 4046510 meaning this is a 1974 3 cyl 65 hp engine.

Now that I know what schematic to use, I have another problem!! The schematic tells me to run the white and brown wires to a switch box and there isn't any switch box on my engine. It was removed. I ran the white wire to the positive side of the coil because it's hot when ignition ios on.

But I do not know where to run the brown wire. That and how to check the celenoid is all I need to know.

Thanks,

Jim

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Jim, the engine has to have a switch box to run, if you try to hook it up to 12v. without one you are gone to burn up very expencive componets, don't try it. Are you sure there is not a switch box it should be on the support bracket ahead of the carbs. as you face the rear or the boat the box should have the wire terminals to your left or starboard side. If it don't you are going to have to get one, the most common problem with those engines ign was the trigger which went bad once in a while the cost about $250 new at retail and are only used on the 3 cyl. engines with battery CD. If you don't want to spend the money for a new or used one (I wouldn't) till you know if the rest of the system is good you can test it with a switch box for a 4 or 6 cyl battery CD that was used for many years one Mercury outboards. Let us know what you find. Back to the wires the brown was for the old style tach thats not available any more so you don't need it and the white is the 12v. wire for the ign. system---Bob

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial


Oh no! It's late at nite now but earlier today we tried to get it running. It ran but wouldn't run well. It idled but wouldn't accellerate.

We stopped thinking we had carberueter problems. When we used the choke gas ran out of the carb afterwards. We have no history on this engine.

I sure hope I didn't burn anything up. What does the switchbox do? Can I test the trigger w/o a 4 or 6 cyl cd? I don't have one. Where are you located?

Thanks,

Jim

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial



P.S. compression is between 125 to 135 lbs on all three and it holds pretty good. So the engine should be in pretty good condition if I didn't burn up any expensive parts. i sure hope not!

Jim

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Jim, if it ran then you sure didn't hurt anything and must have found the connections at the switch box, if I were you the first thing I would do is remove the dist. cap and check and clean the cap,DON'T TRY TO REMOVE THE ROTOR it is part of the shaft and will break. As long as the spark advance and throttle linkage is moving and it still won't take throttle, you will have to clean the carbs. and while your at it install a fuel pump kit they are very inexpencive---Bob

 

[ricksrster]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Laddies,
If he still wanted to use a tach, couldn't he hook up the brown wire to one of the yellow wires on the rectifier? trimjimoo7, your wiring harness is avaiable at bammaine.com. The part number is 84-60795.

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Yes,Thats exactly the way to convert a old engine over to a new style tach Rick

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Here's a couple pics I cannot find a switch box? What should I do? I wired 12V from the control box wiring harness direct to the Coil ( looks just like a car coil).

I cannot find a switch box? What should I do? Do I need one?

null

 

[Laddies]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

Jim, the pictures don 't come up for me

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

I'll try again

 

[trimjim007]

Re: 3 cyl 65hp Merc wiring cable problem & no serial

I tried again and got an error saying that each individual picture was too big. I don't know how to make a pic smaller. So I can't send a pic's of the engine.

Believe me!, there is no switch box on this engine.??? There may have been but there is not one on her now?

She ran yesterday but only idled. Higher revs didn't work. I thought at the time that she needed a tune up. But I don't want to try starting her again until I know, because I do not want to burn out something like Laddies said.

It says 650 Mercury on the split cowling which is hinbged at back . On the front chrome cover it says thunderbolt ignition. The serial number on the engine is 4046510. It is a 3 cylinder with a coil that looks just like a car's coil. It also has a distributer.

Can anyone tell from this information whether or not I need to purchase a switch box ??? If I do not need one I will go ahead and attempt a general tune up (points, plugs, condensor, carb clean-up, etc.

But If I need another very expensive part, I may have to back out. Can anyone tell me for sure????

Thanks,

Jim