Mercury 500 Thunderbolt - Sat for a very long time.

[Loozerdk]

Hi guys, new user here.

Been looking into buying my very first boat, and of cause an outboard engine to go with it, i finally decided on a Mercury 500 outboard, and got one very cheap - but it has not been run since sometime in the 90's.

A little history on the engine:
1 owner since new, very well taken care of outboard, owner was sailing when the engine started to cut out, and they decided not to use it anymore, and just bought a new one instead and stored the old one in a garage since, the engine was running when put away.

My hope is to get the engine running again, and being able to use it on my very first boat, but a do need a few pointers on where to start, never worked on old outboards before, but got plenty of experince on two and four stroke engines, cars, motorbikes, scooters and so on.

Got a Service manual with the engine, but unfortunately its for a newer style of Mercury 500 series, the book is from serial number: 9136250 and up, and the engine is 9048514, so an older version.

Let me get to the problems:
The steering swirl is stuck, engine cant turn from side to side, and tips on how to free that up ?
What do to before trying to start the engine ? it does crank freely, good compression on all 4 cylinders, carbs most likely needs to be serviced, impeller also, since its been sitting for so long, it only has a pullstart, no electric.
Any thoughts about the cutting out part ? Mechanic said it was the mercury tilt switch on the engine making problems, but i can't locate it on the engine, thinking maybe its gone already, or maybe never was there on the old style Merc.

Will add a few pictures of the engine.


Kind Regards
Ronni

 

[gm280]

Loozerdk, you stated the compression was good, but didn't say what it was on the four cylinders. I would do a compression test first then if those numbers were good, see what spark looked like using a spark tester like this;


See if all cylinders can jump a 7/16" gap. If so then go to the carbs. I would buy carb kits and disassembly them and clean them and install the kits. And also replace the water impeller as well and lower foot oil. Once you get it running, then replace the plugs. But also the fuel lines, rebuild the fuel pump and even new plug wires. Old age really works on such parts. And buy the correct shop manual as well. JMHO

 

[Loozerdk]

Hi, and thanks for the answer.

I did not check compression using gauge, just by feel, and all 4 cylinders does feel equal, i know that can't be used for anything, so will check compression using my gauge later today, and get back to you with the numbers, but im positive its just fine.

I did however pull all 4 plugs, they look pretty new, a bit black, but nothing i would worry about, will check spark - but don't own a spark tester, never had use for it, i normally just pull the cap of the lead, and check that way, will that work on an outboard also ?

 

[60sboater]

Knowing how far the spark jumps is an indication of how strong ignition is to a particular plug.

 

[Loozerdk]

Knowing how far the spark jumps is an indication of how strong ignition is to a particular plug.

That i do know. Thats why i normally keep the sparkplug wire around one centimeter away from the ground, if the spark can jump that, its normally fine.

 

[gm280]

That i do know. Thats why i normally keep the sparkplug wire around one centimeter away from the ground, if the spark can jump that, its normally fine.

Yes that is basically right. But it has to have not only the ability to jump that far, but also with a good blue snapping sound and spark too. If it is a weakish yellowish jump, it is not good enough to fire constantly. And that is why a spark tester is so good. It can be adjusted for such jumps (usually 7/16") and will be the exact same for each cylinder too. And since they cost about $10 dollars or less at any auto parts store, buying one is a good idea. Then there is no interpations. JMHO

 

[GA_Boater]

To free the swivel, there is a zerk fitting under a rubber cover on the port side of the swivel, about where the circle is in the snip below. Pump some fresh grease in. If that doesn't free it up, try some heat to soften the old, hardened grease.




She's a pull start, but is it a tiller motor? I can't tell from the pic.

 

[jimmbo]

The mercury tilt switch usually doesn't cause too much trouble as there are no moving parts to break/wear. The wire used during that period has shown to be prone to cracked insulation, and the resulting internal corrosion can make for intermittent connection.
Not all your engine is the same age, the cowl wrap and the face place(red stripes) are several years older than the lower cowl cover(blue stripes). Looking at the ignition coil and the fuel pump, it is pre 1975. You say the steering swivel is seized? Well, it might be from dried out grease, or corrosion. You can try adding grease thru the grease fitting, and slowly wiggling it back and forth. Have you checked to see if there is any oil in the gear case? The fuel lines will need replacing as they were made before some idiots mandated that ethanol be added to gasoline, and they will decompose when exposed to it. As the engine has sat for over 25 yrs, unlikely prepared for storage, it is difficult to know what mess in in the carbs. They may have internal passageways clogged with varnish.

 

[GA_Boater]

Going by the serial number 9048514, is this a Belgium made motor? The front of the swivel/clamp between the clamp screws should have a plate with the serial number and where it is made.

 

[Loozerdk]

It is made in Belgium, and according to the serial a 1974 model.

Had to get another compression gauge, and the readings going from the top to down are:
120 psi
118 psi
120 psi
108 psi

Compression test was done without full throttle. (I know it should be done with full throttle, but forgot to open it before starting)

So the last one is maybe a bit low, but it could maybe be a sticking piston ring, or just normal wear and tear, should i worry ?

Im not positive if the engine was prepared for storage, but i would think so - i know the original owner was pulling the cord every now and so often to prevent the engine from siezen up.

I did get my hands on a spark tester, but unfortunately the incandescent light bulb type, but there is spark on all 4 cylinders, will still have to check how strong it is. I don't know excatly what a tiller motor is when talking about outboards, sorry english is not my native language, so i do make a fair bit of mistakes.

Will try and regrease that swivel, it had to sieze from just standing, with a bit of luck it will let go.

Thank you so much everyone for the help so far.

Kind regards
Ronni

Edit: After a bit google help, i now know what a tiller is, and no - its not that kind, if i understand correctly its the handle with throttle and such to steer the outboard with ?

 

[racerone]

Fact---Throttle position does NOT MATTER when doing a compression test on this 2 stroke motor.---Some will argue but it is a true fact.

 

[Loozerdk]

Fact---Throttle position does NOT MATTER when doing a compression test on this 2 stroke motor.---Some will argue but it is a true fact.

Then i learned something new, so the compression readings i got should mean its a good engine ?

 

[GA_Boater]

Then i learned something new, so the compression readings i got should mean its a good engine ?

Maybe - It means the motor has good compression.

Carbs can still have problems and after sitting so long, they should be rebuilt. Fuel hoses can be deteriorated. You still have a few things to look at and see if the motor will run.

 

[Loozerdk]

Maybe - It means the motor has good compression.

Carbs can still have problems and after sitting so long, they should be rebuilt. Fuel hoses can be deteriorated. You still have a few things to look at and see if the motor will run.

Carbs im not so worried about, done plenty of carb rebuilds and cleaning before, fuel hoses will be changed before engine will go on a boat but i will try to start the engine before replacing those - no reason of putting money in something that will never run, but i do have very high hopes that the engine is just fine, and it will live to go boating another day.

Got the engine broken free, but its very hard to turn, i am affraid it ends with a total teardown to get the steering swivel apart, so it can be cleaned and regreased. Already used an entire tube of grease to try and push out the old stuff, but without much luck yet - grease is pouring out of the bottom, so it looks like its siezed in the top.

As of now it moves, but only with some considerably force.

 

[GA_Boater]

Just keep turning it from side to side, it should loosen. If you can turn it and pump grease in at the same time, it might free up a little easier.

At this point I would hook up muffs and squirt some pre-mix in the carbs and start yanking the pull start. If it pops or fires off, you know the basics are there to spend some money.

 

[Loozerdk]

Just drained the gear lube and it was mostly water with some oil in it, there must be a bad seal somewhere ? I was also looking at the pivot tube, its pretty well rusty, will add a picture later, i wonder if its worth to try and save, or its better just to start finding new parts, and rebuild the engine ?

 

[Loozerdk]

Pictures, i see oil became pretty black, so it looks like only the first part was water.

 

[GA_Boater]

The tilt tube can be changed and It's not expensive after you see if she will run.

What kind of steering will you be using? The tilt tube may not need changing if the steering cable does not go through the tilt tube.

 

[Loozerdk]

The tilt tube can be changed and It's not expensive after you see if she will run.

What kind of steering will you be using? The tilt tube may not need changing if the steering cable does not go through the tilt tube.

Not positive on what kind of steering yet, still looking at my options, there is a few boats in my price range, hoping to buy next weekend with a little bit of luck.

I will try and dump some premix into the carbs later today, and see if there is any life, if i can figure out how to access the carbs, better look in the service manual.

 

[GA_Boater]

Squirt the premix in the spark plug holes. All you want is some pops, not to run for any length of time.

Also the pre-mix lubes the pistons and rings a little.