mercury 650ss 1967 4 cyl

[MERCMAN]

Hi mate,
A 1973 4 cyl 850 powerhead has the same stud pattern as the I6 blocks of the same era. Be careful, gearbox ratio's are different.

I have a feeling the 1971 4 cyl 650 will have a different stud pattern to your original 1967 650 Franken Merc. Maybe not?

FYI, The pistons from an early 650 will fit some of the early 90Ci I6 Mercs
       The pistons from a '70's 4 cyl 800 & 850 will fit all 99Ci I6 Mercs. (high HP I6's, have bigger ports (windows) in the sides of the pistons)

MERCMAN.

[antman]

Hi mate
 your scaring me
so i took old powerhead out of coffin and it fits the new leg and  both blocks say 834-3997 
stud pattern matches . thats good hey

[MERCMAN]

You're in luck! Good work.

MERCMAN.

[antman]

has factory lead seal on crank case bolt

[antman]

looks good but i think no compression ..49 years old and still a factory seal .never been opened
 the guy before rewired stator ,and dizzy
dizzy is stuffed lol , he broke the rotor of the shaft and rewired the internal . now all bulging and also bent disk .hes also removed the flywheel of the pulley
hopefully one of the flywheels of the 850 will do, or i use the old flywheel and stator . i have 2  matching switch boxes for 650
my mate got another 850  so now 4 powerheads  and still cheaper than a used block and postage from the states
will steal the dizzy from the 850 its a match for the   new 650  but different linkages
1 850 has no lower gearbox unit (apparenly shattered at sea
the other has a crack running from prop toward gearbox underneath 2.5 inches long  repairable ?
still a alot of r and d too go

[MERCMAN]

re the compression.. On the Port side of the block, you should see two transfer port covers. These are held in place with rather large Phillips head screws, remove the screws and gently prise the covers off. This will allow you to look at the sides of the pistons and the rings and look across and you'll see the bore on the other side. To move the pistons, you'll need to re-install the crankshaft key and push the flywheel on by hand. No need to do up the nut for this exercise.
This inspection, is a quick and easy way to determine if the pots or pistons are US or possibly OK?
 
Something is telling me the firing order of an older 650 and a newer 850 is somewhat different. I would stick with the 650 flywheel.

The crack in the gear case is usually caused by water lying at the bottom of the inside of the hub for a period of time. The "carrier" will expand and then the case (oysters) cracks. If the carrier still has a good seal near the prop, the oil should be still free of water which means the case can be welded (by an ace). If there is ware in the gearbox oil, chuck the lot.

MERCMAN.
 

[antman]

havnt done much too cold outside
but pulling things apart
these impellers seem to be almost to big for the housing
but same on both legs from 65hp

[MERCMAN]

Hi mate,
The impeller is the correct one, albeit requiring replacement. However, I can understand your assumption should you be use to dismantling OMC water pumps.

This Merc impeller is arguably the most interchangeable component (between Merc models) from the early 1960's through to the 2.5ltr Mec V6's of more recent times.

Remember, after you have seated the new impeller on the pump base and are about to press the the pump housing on top of the impeller, make sure you rotate the drive shaft (not prop shaft) clockwise until the housing seats.  

If you have any plumbers silicone (for O rings and rubber washers etc) smear it inside the pump housing and onto the top side of the stainless steel pump base plate, before reassembly.

MERCMAN.

[antman]

as always thanks
https://youtu.be/hK6qbQwLoMo
link to  last run video when it dies

[MERCMAN]

eek!
That video is hard to watch, I shed a tear.  

I note your video says you were at WOT when the seize occurred.
Do you know what RPM you have at WOT? By the sound of your motor, you weren't within the recommended WOT RPM range. This could mean you have a propeller with too much pitch for the given load. This can lead to other nasty issues, if not corrected.

MERCMAN.

[antman]

i think 4800-4900
before it was 3600 with the crap prop but this prop had mercury code on it and is 48 77342a4 15p
do you think rev
2 high ?
too low?
or does it sound like its running on 3 cylinders already?

[MERCMAN]

Hi,
I'm unsure (confused) as to witch block you have fitted?
If 4 cyl 850 the recommend WOT range is 4800 to 5500
if 4 cyl 650 the recommended WOT range is 4800 to 5200 or there abouts.

I can't figure why you are only achieving only 4900 with a 15" pitch prop?  Have you got the correct gearbox fitted to the block you are running? They are different ratios.
What position is your tilt pin, if hole one, try hole two or three. You hull may have too much wetted surface when planing?

MERCMAN.