Hey, so digging into this motor a bit, pulled head to take a peak. What do you think about these cylinder walls? I do notice that I can rock pistions at TDC a bit. Motor run fine on hose when I bought, no unusual mechanical noise.
As I can see in the pics it looks pretty decent.
If no scores in the walls.......no problem.
Rocking (backlash) at TDC is normal.
Check compression and if it is 120 PSI and up on all cylinders...... run it.
Most important is that the compression is almost equal, not more then 10% difference.
If I am not wrong one of the cylinders on these 70Hp has a bit lower number at the compression.
Cool. Well the only issue was compression was low on gauge from the prior owner 90 in all 3. I bought anyway for heck of it. Cold engine, throttle closed. Could 90 in all 3 be right?
The compression of 90# is low.
But that could be the gauge???
The good: all 3 at 90#
Nordin some years the 120 had lower comp on the #1 and #4
I believe the 70 was designed for all cyl. t be the same.
The gauge and procedure can make a difference.
Cheap Harbor Freight gauges can give bad results.
Was selling a 225 Mercury.
The buyer brought a new HF gauge.
Started comp test and got 85# on #1 and 85# on #2
The pressure was supposed to be 150#
I stopped him and made him use my tester,
My tester read 150# on all 6 cyl.
Buy just a new ignition switch. 30 weight engine oil for the trim pump, or at least on the older models (others will respond). Sierra parts are good aftermarket stuff.
Hey all, about to put head back on. Do any of the head bolts need sealer on them? Also the manuals list two different torque specs by serial number (mine is unknown to me as the sticker is faded - is it listed in more places)??
Thanks, cannot find a 70hp manual there. Can you point this to me? Also, I dont have a serial number so not sure that a manual will help this issue. Is there a big difference bw the two torque specs? Thanks
Pics does not says everything but from what I can see there are no scores.
If you make a compression test and it shows 120PSI or more and the numbers are about equal then I would run it as is.
If you maintain and do not run the hell out of it, it will last for a long time.
You can disassemble the pistons and measure the bore to check how much out of spec it is, but I would not do that.
I would run it if it shows good numbers from compression test.
