Just trying to understand WHAT I could have done wrong here, and any thoughts would be appreciated.
I recently decided to take my 1996 30 HP Johnson apart, and try and get some more compression "on the cheap".. It had been overheated, was running and starting poorly.. I know now that I should not have even bothered without getting the block bored, but took a chance... It had 90 PSI both cyls after the overheat event... I honed the bores, they looked pretty good, installed 2 new standard size NOS OMC pistons, and a new set of standard NOS OMC rings. Everything looked good, no major issues... all back together looking fine..
So now, reinstalled motor, and started to assemble all components- I find that I cannot install the sensor coil onto the block boss,it just does not fit.. Polished the boss, polished the brass bushing in the coil, but can only get a super tight "forced on" fit, and the coil assembly won't turn.. It should turn freely... The block parts fit together fine, no binding, all bolts went in easily and were torqued to spec, crank turns easily and quietly, I used proper anerobic sealer on the block mating surfaces,engine has compression, but it seems that something has to be misaligned by a thousandth or two.. I separated the coil off the block quickly and easily during removal, never hit or dropped anything, no burrs, scratches, roughness anywhere..
Compresssion came up some but not enough.. Went from 90 to 96 on #1 and 90 to 106 on #2... I gambled on lost, but still would have a running motor if the coil assembly would fit..
I have several hundred in this motor, but now am gun shy about going any further as I feel like maybe I tweaked something during assembly.. Everything seems fine, spins fine, I just don't get it.. At one point I took the coil assembly off, reinstalled the flywheel so I could spin it with the starter, and thats when I found that the compression did not come up enough...
As far as the coil assembly binding, Could I somehow have positioned the crankcase halves out of whack?.. All the crankcase bolts are in and torqued... Everything lined up... I just don't understand where I screwed up, but I had to at some point.. The aluminum and brass is not going to change dimension over the course of a few weeks just sitting on a work bench... I'm about done, and will just sell this thing as a clean parts motor, or keep it for parts if I can find a similar one... I would really like some thoughts from those that have had a lot of these engines apart as to where I went wrong... bob
I recently decided to take my 1996 30 HP Johnson apart, and try and get some more compression "on the cheap".. It had been overheated, was running and starting poorly.. I know now that I should not have even bothered without getting the block bored, but took a chance... It had 90 PSI both cyls after the overheat event... I honed the bores, they looked pretty good, installed 2 new standard size NOS OMC pistons, and a new set of standard NOS OMC rings. Everything looked good, no major issues... all back together looking fine..
So now, reinstalled motor, and started to assemble all components- I find that I cannot install the sensor coil onto the block boss,it just does not fit.. Polished the boss, polished the brass bushing in the coil, but can only get a super tight "forced on" fit, and the coil assembly won't turn.. It should turn freely... The block parts fit together fine, no binding, all bolts went in easily and were torqued to spec, crank turns easily and quietly, I used proper anerobic sealer on the block mating surfaces,engine has compression, but it seems that something has to be misaligned by a thousandth or two.. I separated the coil off the block quickly and easily during removal, never hit or dropped anything, no burrs, scratches, roughness anywhere..
Compresssion came up some but not enough.. Went from 90 to 96 on #1 and 90 to 106 on #2... I gambled on lost, but still would have a running motor if the coil assembly would fit..
I have several hundred in this motor, but now am gun shy about going any further as I feel like maybe I tweaked something during assembly.. Everything seems fine, spins fine, I just don't get it.. At one point I took the coil assembly off, reinstalled the flywheel so I could spin it with the starter, and thats when I found that the compression did not come up enough...
As far as the coil assembly binding, Could I somehow have positioned the crankcase halves out of whack?.. All the crankcase bolts are in and torqued... Everything lined up... I just don't understand where I screwed up, but I had to at some point.. The aluminum and brass is not going to change dimension over the course of a few weeks just sitting on a work bench... I'm about done, and will just sell this thing as a clean parts motor, or keep it for parts if I can find a similar one... I would really like some thoughts from those that have had a lot of these engines apart as to where I went wrong... bob