50 HP Thunderbolt - stupid problem

[Johnny Otter]

Hi all, just found this forum, and think it's just what I need . I'm helping a friend out and we are stuck.
I have a couple of questions. The first is simply identifying the year of the engine. The serial number is 3326772A1. I've had a look on some other sites, but can't find a UK reference (if there is one!). The codes seem to refer to a 4 cyl model from 1972, although I would have thought it was more recent than that.
The second question I'm almost embarrassed to ask. How on earth does the engine lift? Is it electrically operated, or manually? I know there is a locking bar through the unit, which presumably changes the angle, and I can see two 'claws' around the bar, which I presume need to be released in order to lift the engine. Would I be correct in thinking that the two dampers are purely to assist the raising and lowering of the engine due to its weight, and as a method of control should the prop hit something and to stop the unit flying upwards?
The engine is electric start, and I've tried the throttle in forward, reverse and neutral to try and raise it.
The whole point is to get the prop in a barrel to get it running, but as we can't lift it, we can't start it
Any help gratefully appreciated.
Thanks,
John

 

[tmcalavy]

Re: 50 HP Thunderbolt - stupid problem

You have a sweet outboard, one the best Merc ever made. I used to have a 73 same model and hp. The motor lock will disengage when the motor is in one of the two gears, F or Reverse, I forget which. Your post doesn't say whether it is still on the boat, but I'm guessing it is. The control up by the steering wheel is either one or two lever...with two levers, one operates the throttle, the other shifts...with one lever you shift and throttle at the same time...push forward shift into F, pull back shift into Reverse, Neutral is straight up. Move the shift control until the motor lock disengages. Not an easy motor to lift, but it's easier if you have a outboard lift bar available at most marinas/boat shops, etc. You set this gismo on top of the outboard when you're in the boat and lever the handle down towards the boat floor...lifts it smartly with little effort/strain.

 

[ricksrster]

Re: 50 HP Thunderbolt - stupid problem

The motor lock (reverse lock) engages in reverse. It keeps the motor from flying out of the water when reverse is engaged. Put the control in neutral. You will want it there to start the motor anyway.

The lock or the rod that engages it may be Stuck or frozen up. PB blaster might loosen it up. Make sure you grease things when you get it working.

It operates by a cam in the lower unit where the shift rod enters the lower unit. Check to make sure the cam isn't too worn out.

While you have the lower unit off, change the impeller if it hasn't been done in a couple years.

A Mercury Service Manual comes in very handy on old outboards. They are easy to follow and eliminate the guess work.

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Thanks for the replies guys, much appreciated. I'll give it another go and see how I get on. The annoying thing is, my friend lowered the engine a few weeks ago when he got the boat, but he can't remember how he did it! I'll have a look on ebay and see if I can get a service manual for it. I want to have a look at the impeller anyway, and do an oil change on it, as I don't know when it was last done. The plugs are clean, and I have seen the engine running some months back in a boatyard, and it started well and sounded sweet.

Now, if I can just get the engine raised, we'll be cooking on gas!
Regards
John

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Hi guys, got it sorted! Had my son push the throttle forward and reverse and I was underneath watching. As you rightly pointed out, once it was pushed fully forward, the claws released enough for me to lift the unit. Did it a couple of times, greased it as well, so fingers crossed.
I'm off to order my manual. Do you think I'm on safe ground with that serial number to gauge the year?
Thanks again,
John

 

[ricksrster]

Re: 50 HP Thunderbolt - stupid problem

Does an have an ignition driver and coil?

 

[tmcalavy]

Re: 50 HP Thunderbolt - stupid problem

Look for a Merc factory service manual, it will tell you all the details of the Thunderbolt ignition...it has distributor and coil but can't remember much beyond that. Interesting system and very reliable if it's sound.

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

I'll have a look under the cowling tonight and see what's in it. I've ordered a manual on ebay. The unit is a blueband - not sure if that is relevent or not?
Regards,
John

 

[wrxcobra]

Re: 50 HP Thunderbolt - stupid problem

Hi john
I am new to the forum also, its a great sit with loads of good information, I had a problem getting the year of a 850 85 HP blueband, have a look at this site it has loads of parts, and i am sure you will find a manual there, also if you look at the parts section you can narrow the year down, by parts that are on your model but not on earlier or later models.
My ob was a 1976 or 1977 I found this out by earlier models there is a distributor available in the spare parts and mine has electronic, things like that.
Good luck

http://www.oldmercs.com/faq.html
Daniel

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Hi guys, finally got my manual off ebay, so am having a browse through it!
One more silly question, if I may. Now that we have succeeded in tilting the engine, when travelling on the trailer, should the engine be tilted? The reason I ask is that when it is tilted, and the two swivels are holding it up, I cannot see how to anchor the engine without it bouncing up and down!
Do I just need to put a wooden support through the brackets, or is there a 'proper' way to secure it?
Thanks again,
Best wishes,
John

 

[OldMercsRule]

Re: 50 HP Thunderbolt - stupid problem

Do Not dry shift into reverse. You will be sorry: eventually. The lock is released in forward, (as I think you now know). JR

 

[OldMercsRule]

Re: 50 HP Thunderbolt - stupid problem

Hi guys, finally got my manual off ebay, so am having a browse through it!
One more silly question, if I may. Now that we have succeeded in tilting the engine, when travelling on the trailer, should the engine be tilted?

Yes, as it could drag the skeg: otherwise.

The reason I ask is that when it is tilted, and the two swivels are holding it up, I cannot see how to anchor the engine without it bouncing up and down!

You should find a small bracket at the base of the power head that should rotate to keep the motor in the up position.

Do I just need to put a wooden support through the brackets, or is there a 'proper' way to secure it?

A wooden block under the power head would work also. I run larger heavier engines, (inline sixes) and I use: "transom savers" that hold the engine up from the lowest point on the engine directly to the trailer. That stops the constant wracking of the motor on the transom. If the boat is the same vintage as your motor, the transom may be weaker then you would like, and a motor working constantly while you tow will not be a good thing.

Thanks again,
Best wishes,
John

Hope this helps, JR

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Thanks for the great advice again guys (especially about not dry shifting into reverse).
Anyway, got the engine in a barrel of water and she fired up great. The only thing that concerns me slightly is the fact that the water coming out of the engine is tap hot, even after running for a couple of minutes. The Evinrude 30HP on my friend's old boat always came out only very slightly worn.
Is this the norm, or could it be the impeller not working properly (although it does come out at a fairly strong jet)?

With regard to securing the engine for towing, I can not see any obvious bracket apart from the two swivels which the engine sits on in the tilted position, but the boat engine would be bouncing about all over the place if it wasn't chocked down.

As you guys are so very helpful, and it is very much appreciated, I noticed one other thing that is confusing me. In between the engine housing where the lever is that locks the claws, there is a thin pipe not connected to anything. It goes down into the lower part of the engine, but I cannot see where it ends up. The end of the pipe is almost like a fuel line, and is corrugated as if another hose fits over the end of it.

Any thoughts please?

Best wishes,

John

 

[tmcalavy]

Re: 50 HP Thunderbolt - stupid problem

Hey John,
A transom saver, as mentioned in an earlier post, is a bar/pole with a Y on each end. The front of the leg of the outboard cradles in one Y and the other ideally is strapped/cabled to the trailer. It ties the outboard to the trailer so the motor doesn't bounce up and down in transit, putting undue forces/flex on the transom. You can make one yourself, but if you Google transom saver you can find one for not much $$$. The pipe you mention might be a crankcase drain...can't remember exactly...normal and nothing to worry about if it is. The manual should explain it. When the motor is running you should be able to touch the water jackets on either side of the cylinders without scorching/burning your hand...should be cool to warm to the touch, not hot. If it is not, time to check/replace the water pump/impeller or check the water route for obstructions. It will also run warmer in a barrel than on the boat in the water...water is warmer in that confined space. Might want to trailer it to a pond, back the boat/trailer down far enough to submerge the lower unit, fire it up and check the water temp. from the telltale hole then.

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Hi all; well, we got the engine running fine, but I'm a little confused about the pee hole. I've changed the gear lube and started the engine, and everything was going fine, with a strong jet out of the pee hole. After the engine was idling for about 5 mins, the water jet stopped almost completely. We turned the engine off straight away, but is there any likely reason for this to happen?
I went to my local marine store, and when I asked about changing the impeller, the mechanic gave a sharp intake of breath! He reckoned that due to the age of the engine (1972) it would need some heat on the bolts to get them loose.
Is he talking of the three bolts holding the bottom unit of the engine, or bolts holding the impeller once the lower unit has been removed?
I did get a manual off ebay, but having looked at the schematics for the bottom unit, I'm a bit worried about the amount of items around the impeller in order to change it. As well as the impeller (if that is the problem) are there any gaskets etc. that would need to be changed at the same time?
Many thanks again, as ever.
Regards,
John

 

[jebeebe]

Re: 50 HP Thunderbolt - stupid problem

he is probably talking about the three bolts that holds the upper half of the pump to the lower half. The impeller is inside driven with a small key. Under the lower half of the pump is a O-ring(outer) and a seal (inner) and below that is the driveshaft berring. I would suggest replaceing the whole pump but you might get by just replaceing the impeller..............Jerry

 

[tmcalavy]

Re: 50 HP Thunderbolt - stupid problem

It's a fairly easy maintenance item to do, if it hasn't been in salt water. That could cause the corrosion/bolt problem he mentioned. If not, piece of cake. There are four, if I remember correctly, bolts holding the leg together...two on each side and one under the trim fin/anode that hangs down right above the prop. Manual says to have it in N when you drop the lower...I found it easier to drop it in Forward instead. The pump/impeller is easy to change...the challenge is getting the lower back on the last inch or so...takes patience and some preferably cold and tasty beverages at hand, but it goes easy after you conquer it the first time. Sweet outboards those 50 hp Mercs...wish I still had mine, but current boat wouldn't accomodate it. It won't pee much at idle on the muffs...but should pick up steadily if you boost the rpms a little...don't go over 1000 or so. Given some back pressure in the water it will put out a good stream with a new pump/impeller. Check the driveshaft for pitting when you change the pump...a pitted shaft can cause water intrusion in the lower unit...had to remove mine, have it built up and then turned back down smooth. Not too expensive, but delayed us getting on the water.

 

[Johnny Otter]

Re: 50 HP Thunderbolt - stupid problem

Hi guys, well, we finally got the boat launched, and the engine ran sweet as a nut. The problem was, the weather was foul, and we had only one hour's fishing in the whole 10 days!!

My friend has decided that this boat isn't for him though, and has now sold it and bought a more robust fishing boat. This one has a 130 HP Yamaha saltwater outboard on it, so I'm off to do some research on that for him!

Many, many thanks for all of your replies and help. We wouldn't have got there without you!

See you in the Yamaha forums maybe,

Best wishes,

John