72 Mercury 500 No Spark

[RRafkin72]

The 69s, had the nicest Cowl Decal that Mercury ever had
If the Lower unit came off of a 4 cylinder 65hp, 75hp, 80hp or 85hp, it will have the proper gear ratio for any of those engines. Hopefully the shaft lengths match and are correct for you boat
Myself, I like the post 78 cases better, slightly better Hydrodynamics
A case off of the Inline 6s will also fit, but the gear ratio will be wrong
None of the gearcases above will fit on the 50hp.

If you buy them, take the water pump apart and install a new Impeller. What kind of Compression Numbers does the powerhead have?
While I like these engines, parts are getting harder to find, the last 4 cylinder 65, was a 1972, 50 yrs ago.

Edit: As pointed out below, the last 4 cylinder 65 was in 71. In 72, the oddball 3 cylinder was introduced

Thats the info I needed, thanks a bunch.
They both say 20" shaft and inline 4
The 65 is saying cyl. 1,2,3 have 125psi and cyl4 has 105. Currently starts and runs.

 

[jimmbo]

That is a difference greater than 15%.

 

[RRafkin72]

That is a difference greater than 15%.

I understand its not ideal but puts me in a better situation than I'm in currently. I may still try and get the 50hp runnin and then sell it to re coop some funds. Who knows it might free up the rings when it fires. But I still need a $450 switch box just to try... I went to remove the top cover to inspect pistons and immediately broke a bolt. And I soaked it with pb blaster. Tried a second and it felt the same so I stopped and weighed out my options. That amongst the cracked coil and plug wires. Cracked stator wiring and other stuff. Id just rather be boating than fixing. Currently have a 79 harley shovelhead chopper that needs finishing and a 76 chevy van that could use a whole lotta love too...and so it goes

 

[RRafkin72]

I went ahead and purchased both the 69 engine and the 70 lower heres a few more pics of both

 

[RRafkin72]

The boat and the land yacht

 

[racerone]

?---What cover where you trying to remove to inspect pistons ?----A bypass cover or the cover around the sparkplugs?------Only by removing bypass covers on the side of the block can you inspect pistons !

 

[RRafkin72]

?---What cover where you trying to remove to inspect pistons ?----A bypass cover or the cover around the sparkplugs?------Only by removing bypass covers on the side of the block can you inspect pistons !

Forgive me I dont know what Mercury calls it. The cover with the spark plugs...so I could inspect the top of the pistons. There's about 10 or so 5/16" steel bolts goin thru the aluminum cover and block with a captured nut on the back side. On the 2nd bolt I tried to remove I watched the head of the bolt spin and not the end in the nut and at that point decided to hold off on tearing down. Hoping I get the 50hp running eventually with a just new switch box and some wiring then either keep as a spare or sell it.

 

[jimmbo]

Forgive me I dont know what Mercury calls it. The cover with the spark plugs...so I could inspect the top of the pistons. There's about 10 or so 5/16" steel bolts goin thru the aluminum cover and block with a captured nut on the back side. On the 2nd bolt I tried to remove I watched the head of the bolt spin and not the end in the nut and at that point decided to hold off on tearing down. Hoping I get the 50hp running eventually with a just new switch box and some wiring then either keep as a spare or sell it.

Remove that water jacket cover and this is what you will see. That engine does not have a removable Cylinder head

 

[racerone]

Hence the reason for the question in post #26.-----Tried to save you time and aggravation.-----No need to remove that water jacket cover.-----You won't see anything you can not see through the sparkplug hole !-----Remove bypass covers on the side.----A much easier task.

 

[RRafkin72]

Hence the reason for the question in post #26.-----Tried to save you time and aggravation.-----No need to remove that water jacket cover.-----You won't see anything you can not see through the sparkplug hole !-----Remove bypass covers on the side.----A much easier task.

Ahhha of course. Glad I said something (because sometimes I'm too proud to admit I broke something). And real glad I didn't learn the hard way and keep going for it. thank you guys. I guess I snapped the bolt for a reason...to steer me away from removing unnecessary stuff

I should be able to get another compression guage on the 50 horse tonight and verify.

What chance do yall think rings could free up after it fires for the first time in a while?

 

[racerone]

??-----Why not take the bypass cover off to do an inspection?----Easy as can be.----Starboard side of the motor.

 

[RRafkin72]

??-----Why not take the bypass cover off to do an inspection?----Easy as can be.----Starboard side of the motor.

I'm still planning on it to at least know where its at. Are both side covers bypass covers or just the stbd side?
I did get another guage on it and seems 90-100 psi is accurate unfortunately

 

[jimmbo]

On the port side is the exhaust cover. You really don't want to try removing that. On average more than 1/2 the Bolts break when there are attempts to remove them.

 

[RRafkin72]

Got around to draining the lower and it's milky. I believe that indicates bad shaft seals correct?



Also without removing it I can't really tell if it can just be reversed, but I want to setup my lever head and helm wheel on the stbd side. And to me it doesn't really like like it just swaps over sides.

 

[racerone]

That lever can be put on the other side

 

[RRafkin72]

Popped those bypass covers off. The rings still have a little spring in em and pistons don't look too trashed. It's hard to tell with such a small port but there was no bad scoring that I could see

 

[RRafkin72]

New drive showed up yesterday. Removed the water pump housing and impeller right away. Should get one ordered today.
The rubber where the shifting cog is looks a little suspect. What do yall think?

 

[racerone]

That black plastic piece is part of the " REVERSE LOCK " set-up.

 

[RRafkin72]

That black plastic piece is part of the " REVERSE LOCK " set-up.

Is it supposed to have that angle at the end of it? Sort of looks torn or at least worn

 

[jimmbo]

It has been chewed up a bit. They should still be available