Mercury 500 Thunderbolt 50 HP Link and Sync

[lgaytan]

Hello,
I have an old 1976 Merc 500 thunderbolt 50 HP outboard, I want to check and adjust the throttle link and timing synchronization, I got the SELOC manual and it is not very good, the pictures in the book are all black and cant see well the items, I don't seem to find the right model of my outboard there either.
The motor idles good but it seems to be REVed up, I don't have a tachometer yet but will get one this week to confirm revs, anyways, if somebody has some instructions to do this adjustments will be greatly appreciated. The serial number of the motor is 4967035. Se a picture attached of the throttle arm, can some one tellme what is the function of the 4 set screws?

Thanks

 

[merc850]

This should help you have to start on page 1 to do it right and you'll need a timing lite.

 

[lgaytan]

Thank you merc850 this is much clearer than the SELOC, which is the Idle stop screw? I think I have identified all others.

 

[racerone]

Looks like a 78 model.----Picture of the decals on the cowling will help.

 

[lgaytan]

Hi racerone, I will take some pictures later today how ever I believe the cowling cover that wraps around the motor is not original.

 

[merc850]

The manual I have (1975-1978) only shows the instructions I've posted but on further inspection I notice that it's for up to serial Nr. 4576236 the posted picture is for ser. Nr 4576237 and above, so much for downloaded manuals!
I'm scanning the hard copy now.

 

[merc850]

Try these instructions

 

[lgaytan]

Thanks marc850! those images look much more like my outboard I will check later tonight. What is the manual you are taking this scans from? I might want to look to see if there is one available to buy it, looks very good.

 

[lgaytan]

What would be a test tank size for this motor, are there any designs available I could use to try to build one, I live 2.5 hours away from the nearest lake so its not an option to go there just to try the motor. Frequently I have to make the trip and come back quickly after a bad trial.
I usually put the motor in a 200 litre tank that I cut for the motor leg to fit, but I wouldn't be able to speed up the motor there.

 

[merc850]

Usually a 50 gallon oil drum with the motor on boat: the manual is 1975 thru 1978 part Nr. C-90-75512. For low speed setting you can use muffs.

 

[racerone]

Post the compression values on this motor.----Or remove intake bypass covers to inspect pistons and rings.----Serial # is for the 78 model year !

 

[lgaytan]

thanks, I'm bidding now for a used manual.
This weekend I will check compression on the motor, change seals and gaskets on carbs as well, top one is leaking heavily. I will post the compression numbers, hope they are fine I'm right now changing pistons to a Force motor, this Merc is my hope to get me on the water while fixing that other one.

 

[lgaytan]

Hi. I changed gaskets on the carbs and stopped the leaking, now I started the timing procedure but i couldn't find a timing mark on the block, where is it supposed to be? If there is no timing mark I jeed to find TDC and make a mark to align the mark in the flywheel decal to the block right?

 

[lgaytan]

Maybe the timing mark was s this thing that looks broken...

 

[1960 Starflite]

My 850, 4 cyl didn't have a timing bracket/pointer. I placed a dial indicator in #1 sparkplug hole to determine TDC then made a pointer to align with decal.

 

[lgaytan]

Did that last night, seems to be working. Thanks

 

[lgaytan]

Quick update thanks for the support, I took the boat to the lake this weekend and it performed beautifully, no issues with the motor, what a beautiful sound is this old mercs at reving up.

Now I'll start working in the boat, paint is very bad, needs new carpets and love overall, I will switch to the boat repair forums now.

Thanks