Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

oceansoul63

Seaman
Joined
Apr 16, 2008
Messages
59
I just found out the year of this motor from researching the serial number.


Anyway, before I get to the questions, please read the back story. I apologize that it's a bit long, but I want to give as much info as possible on this.



A few months ago, my landlady, who is also a friend, told me she wanted to get a little runabout for herself and her young daughter. She was raised here in St. Augustine and grew up around boats, and wanted to give her daughter the same experience.

She didn't have much money to spend, though. I found a 1967 Sportcraft on eBay that came with a running Mercury 50 HP and trailer, and she was able to buy it for just over $500. A great deal. I went up to Jacksonville and picked it up for her.

The first time we put it in the water, it idled fine, but wouldn't throttle up, even with the handle all the way down. A buddy and I took the cover off, and found that the lines running to the distributor were getting bound on the cowling. After a few adjustments, it was running pretty good. The carb seemed a bit dodgy, but for a 38-year-old motor, it was doing OK.

However, the lower unit was a bit suspect -- when you put it into gear, it would hesitate and make a bit of a grinding sound, then go in gear. My buddy told me he'd help me adjust it the next time he was in town (he lives in Gainesville, FL and I am in St. Augustine, about 75 miles away).

Anyway, we used the boat a few more times, and the motor was performing quite well. We took it all the way down to the Matanzas Inlet and back, and it ran great.

Then, coming back into our inlet, I did something stupid. I used to do a bit of a hotdog move in my old Renken, where I'd make a real tight turn around the channel marker at a pretty good speed. I really should not have done this, but I did it in the Sportcraft.

Well, much to my dismay, when the boat swung around, the motor swung up on one side. Apparently, the starboard motor clamp wasn't fully tightened, and it didn't hold. The port side clamp held, so the motor didn't come off the transom, but it swung into about a 40' angle, bringing the prop out of the water. I instantly shut it down, moved it back into position and tightened both clamps.

Went to start it, and it would run for about 5 seconds, then stall. I kept trying it, to no avail. Got towed back into the ramp by some friends and puller her out of the water.

My neighbor and I fiddled around with it back at home, and got it to idle good without stalling.

Then, my buddy came to town the next weekend, and we fiddled around with it some more. It seemed to be running good again, so we took it to the ramp and put it in the water. It would run fine in neutral, but as soon as you put it in gear, it would stall. He tinkered with it for about an hour without any success. His theory was that it was the distributor, or the carb. He didn't have his tools with him, and he doesn't have much experience with Mercs (he's good with Johhny/Rudes). He told me to find a local marine mechanic, and said it shouldn't be too much to make the proper adjustments.

Keep in mind that this is my landlady's boat, that I talked her into buying, that I feel responsible for screwing up from the hotdog incident. So I'm making it my duty to make this motor right, or buy another running one for her. I'm also really tight financially.

Anyway, she called a couple of places and was referred to a local mechanic who works on old Mercs. She asked me to take it to him. So, I did. When I got there, I immediately had misgivings about the guy. His shop was out in the boonies, and there were all kinds of junked boats strewn about on his property, most with weeds growing through them. It looked more like a junkyard than a repair shop. But, I figured, sometimes those guys are good.

Another red flag was the fact that he had a bunch of German Shepard dogs, some of which were running loose, some of which were caged, some of which were chained up. Now, I'm no dog hater -- quite the opposite, in fact. I love dogs. But these dogs didn't seem like family dogs. More like attack dogs. Oh, also, the whole place stunk to high heaven.

Anyway, this guy comes out, and I tell him exactly what I've told you above. He says OK, leave it here. I said, well, obviously, I'd like you to call me with an estimate before you go doing hundreds of dollars worth of work. My friend had said it shouldn't be more than $100 to make the required adjustments. This guy said he wouldn't even touch it for less than $300 (this was without even looking at the engine yet). I thought that was kind of suspect, but I figured, well, I guess I'm kind of stuck with this, since it's so hard to find mechanics who will even work on these old Mercs. So, I said OK, but please call me if you think it's going to be more than $300.

Now, while I was there, I felt real uneasy about the whole thing. The guy definitely had a sleazy kind of vibe and didn't communicate very well (I couldn't tell what nationality he was, but English was obviously not his first language). I mention that not as any kind of ethnic discrimination, but because the communication process was hindered by it. Not what you want in this kind of a situation.

He told me he wouldn't get to it until later in the week, and I said that was fine. Never once in my presence did he even look at the motor. I really halfway thought about just saying "never mind," and hooking it back up and leaving. And, if it had been solely my decision to make, I probably would have. But my landlady had wanted me to take it to him because some shop she called had recommended him.

So, the very next day, I got a message from him asking me to call him. When I did, he said "You brought me a frozen motor."

I said I did not, that it was running just a couple of days prior. He insisted that it was seized, and that the flywheel would not move. I was very disturbed by this, because I literally had been running the motor just the other day and it was running smoothly (in neutral, anyway.)

So I said, OK, well how much do I owe you, figuring that naturally there would be a bench/diagnostic fee. He said "Well, we agreed on $300."

I said, but that was to do all the work. He said "I did all the work."

I said why would you do the work if the motor was frozen??!!

He said he never tried to start it until AFTER he had done the work, rebuilding the carb, etc.

He said he just based the work on what I told him was the problem.

I said you've gotta be kidding me.

What kind of mechanic would not first try to run the motor to do his own diagnosis before beginning any work???!!! Why would he base it solely on what I told him? I'm not a mechanic -- he is.

In all my years with cars and boats, I've never heard of a mechanic just going ahead and doing work without first examining the situation for himself.

Anyway, he wouldn't give the boat back unless we paid him, so we did. So now we've got a seized up motor with a rebuilt carb.

Now I know it's like $1000 to completely rebuild a motor like this, and I could probably find a running equivalent for less than that.

Now for my questions:

1. Is it possible that the motor is seized because of the lower unit? If so, how do I determine that?

2. If it is the power head, I've read about some stuff called Engine Release that you put into the cylinders to free up a seized outboard. Is this worth attempting? A couple of people I've asked said no, but I've found some online sources that say it does. I figure it might be worth a try -- I mean, at this point, what do we have to lose on this motor?

3. Is all hope lost for this motor? Should I just part it out on eBay and look for another one, or should I pay someone to rebuild it?

4. Lastly, do you think this is directly a result of the above-mentioned hotdog incident? Or is it possible that the motor was on its way out already?

Any advice would be quite welcome. I don't have much money, but I want to make this right for my landlady and her daughter.

Thanks!
 

Laddies

Banned
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Sep 10, 2004
Messages
12,218
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

If you were in charge of the boat when the problem happened it is definitely your fault. If you toke the unit to a repair shop and ask for a price to clean the carbs and thats what you got that is definitely your fault. There is no quick or cheap fix no miracle lube that will fix a seized engine. It would be nice to fell bad for you but you know who is behind the landlady and her daughters problem without anymore being said.
 

oceansoul63

Seaman
Joined
Apr 16, 2008
Messages
59
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

Laddies -- I'm a little surprised at the hostility of your post. Apparently you think I'm looking for some kind of absolution from responsibility, which is not the case at all.

I already stated that I take full responsibility, so I'm not sure why 90 percent of your response is telling me it's my fault. That is not in question here.

I'm also not asking for anyone to feel bad for me. I'm asking for advice on how best to deal with this. The reason I asked question #4 was not to find something else to blame, but to determine exactly whether the seizure of the engine is linked to the incident, or whether there is another cause. I asked that to help determine what might be the problem.

I see by your profile that you are a retired Mercury mechanic. Yet you did not answer any of my actual questions. Could the lower unit, which was suspect cause the engine to lock up? If so, how do I determine that?

And by the way, as for the mechanic I took the motor to, I did not "ask for a price to clean the carbs." I told him what it was doing and that that was what I suspected it could be. What I asked him to do was find out what was wrong. In fact, I adamantly stressed that I wanted him to give me an estimate BEFORE he did anything. Instead, he just went ahead and did the carb work without even attempting to start the engine.

It remains my conviction that any reputable mechanic would do a diagnosis of his own before doing any work.

As for your other comment, I'm not looking for a "miracle." I mentioned a product that I read about and was asking if anybody had experience with it.

If you have tried it and found it to be ineffective, then perhaps your comment is useful. If, as I suspect, this is just pure conjecture on your part, then that is not worth anything to me.

This is the product I found: http://www.enginerelease.com/

Here is another reference I found to it: http://totalautoblog.com/auto/news_2008-02-25-21-50-01-325.html
 
Last edited:

oceansoul63

Seaman
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Apr 16, 2008
Messages
59
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

Also, as far as I knew when I took that motor into the shop, it was not seized up. As I stated, I had run it just a few days prior to taking it in.

The fact that the mechanic did not once try to run the motor before doing that work is, in my opinion, negligent at best.
 

vulkus

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May 2, 2008
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Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

I am not a boat mech, nor do I pretend to be. But when a hillbilly mech says he wants $300 before he will touch it. Sounds like a time to hook it up and leave.

As for your question, unless I am fairly stupid and I don't think I am. I fail to see how your engine seized (except by water ingestion/or bung impeller) between you running it and handing it over to the hillbilly.
Sounds to me like he fekked it through neglect.

As for the engine release, what do you have to loose? You have already spent $300, for a carb rebuild which also sounds rather expensive. I hope he used gold plated screws.
I would use the engine release agent, I am sure you can't stuff it anymore than it already is.

It is entirely possible that the motor was on its last legs before you did your super turn, and the turn made sure it was dead.
Plus I wouldn't be to concerned about being bunched up about the boat. She wanted a boat, she could only afford a certain price. They say you get what you pay for.
You fiddled with it quite a bit before you did your super turn.
 

Sig_Mech

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Jun 25, 2007
Messages
63
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

OS63, sorry to hear about your bad luck but here's the way I see it:
You get what you pay for. If you had a bad feeling about this guy then you should have trusted your gut and left before he touched the motor. No written estimate and no proceedure spelled as to the exact work he will do means that you shouldn't have left it with him.
That being said, if the lower unit seized up then it is possible the powerhead is not turning because of that. Drop the LU and try to spin the flywheel, if it doesn't spin then ya got big problems. If the powerhead is seized then nothing in a can will help get it back to normal. You won't know the extent of the damage until you tear it down. That's the time to decide if you want to part it or fix it.
Good luck.
 

oceansoul63

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Apr 16, 2008
Messages
59
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

Thanks Vulkus and Sig_Mech.

Good advice, and pretty much my thinking on this, as well.

I mean, I certainly know that when you pay $500 to buy a boat, motor and trailer, you're totally rolling the dice. I've owned boats all my life, and I'm well aware that they're holes you pour money into, especially older ones.

What blew my mind was the way this mechanic handled this situation. As I said, I've never heard of a mechanic fixing something without doing some kind of diagnosis of his own. I couldn't believe it when he told me that he hadn't even tried to start it until AFTER he did the work. And to be clear, all I told him was what I suspected was what it needed. I asked him to find out what it was.

But anyway, I'm working on various solutions to this problem. I might just purchase another motor anyway, and then try to see if this one's at all salvageable. At the very least, it's got some very good parts on it.

Also, I definitely would have listened to the inner voice that gave me doubts about this guy had it just been my decision to make. I would have just hooked back up and told him I was going to check with some other people, and left. But my landlady had been referred to this guy and wanted me to leave it there.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

Befrore going too far pull the plugs and see if it will turn.
 

dcatcha

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Jul 25, 2009
Messages
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Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

I have a motor sn 4417697 which I believe is 76-79 motor.. 500 Thunderbolt 50 HP.


I recently had the starter rebuilt, and replaced the solenoid and did not take care in documenting the wiring. Can anyone help me out with locating the color code, and wiring?
 

green4themoney

Petty Officer 1st Class
Joined
Jul 21, 2004
Messages
318
Re: Advice on a 1970 Mercury 500 Thunderbolt Ignition 50 HP Outboard

you probably heard this already but all times the engine is spinning, in the LU (lower unit) its turning a pinion gear which is turning a reverse and a forward gear, both with bearing that can seize and fail for whatever reason and a shift mechanism that can also fail for whatever reason, so like what somebody else said on here quote try dropping the lowerunit and turning the flywheel if its still a no-go you probably do have some larger issues inside your engine, if once the LU is dropped and it spins freely, the problem is in the LU and is not as bad (obviously as having a problem in your powerhead)
 
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