Johnson "70mod"

[filthy phill]

what is the exact model number of the engine ?

•Model . J70TLCCA =1988 ..........J70TLCCA = 1989.............J70PLEEE = 1990 ..........J70TLEIE =1991..........J70TLCCA = 1992.

[filthy phill]

here is a couple of pics to show what OMC done to inside the exhaust cover to improve the cooling of the no 1 and 2 cylinders.
the small hole at the top lets plenty of water get to the top two culinders and any air expelled out the top tell tale fitting on the top of the block.
this simple mod made a lot of difference.
along with changing the timing to 17 deg instead of 19.. seems 19 made it run too hot ? also larger main jets were put in the carbs to stop the motors leaning
out and destroying the pistons and sleeves.

anyway, here is what OMC done to make the later oval port run the best for cooling.

[hupiveneilija]

Its 60tlene. I made that 5/16 hole and all holes from ex cavity side to cylinders little bigger, including that little hole on up. Also made that upper corner on divider wall larger. IMO water must flow.

[hupiveneilija]

Here is more todays achievements. Now like it was ment to be in first time😂😂. Only cleanup and 45* angle on ex ports.

[filthy phill]

so your engine with this number is a 1992 johnson 60hp, this had the small carburettors with the 1.25 venturi.
this model needs the updated water pump and updated exhaust cover and updated thermostat and spring and cover.
it also needs the updated water pump and the stainless plate below the water pump updated. they are different plates and different impellors.
with these improvements and 17deg timing you should not get over heat problems. with everything be normal ..
unless there is problems with the piston clearances, too much will cause piston slap, too little will cause overheat of the metal and scoring obviously.

with all the work your doing it is very important to get plenty of water THROUGH the motor.

Now back to your engine, running at 7,000 rpm plus you need plenty of water to go through the motor, maybe your idea's will let more through,i really dont know.
maybe someone else on here like fast fred can advise on exactly what you need to be doing.

If it was me I would definitely get the improved thermostat and housing and spring so the pressure reliefs let the water through correctly..
you might lose a bit of pressure, but your pressure is pretty high anyway.

did anything happen to any of the bearings when it got hot ? or seals.

.

[hupiveneilija]

Question, wich reeds? CCMS or Boyesen?
CCMS use original stopper plate, Boyesen dont. If boyesen is it okay to use stopper plate with those? They say ditch them. Think that leaving those off would lower cc pressure little bit. Any matter?
What do You prefer?

Did some head volume measurement today. Plug in place.
329835-1 34cc
329835-4 32cc
336306-4 30cc
70mod 21cc

[hupiveneilija]

with all the work your doing it is very important to get plenty of water THROUGH the motor.



If it was me I would definitely get the improved thermostat and housing and spring so the pressure reliefs let the water through correctly..
you might lose a bit of pressure, but your pressure is pretty high anyway.

.

Pressure may drop, have to get flow and volume yes.

[filthy phill]

so your now using another powerhead to modify ?

[hupiveneilija]

Yes , because I dont have .030 useable piston for white ph. Well I do have new set some wisecos and bored ph. Dont want to use it now. Saddly someone has has done some cleanup for it and made same error as I did, moved transfers up when smoothening them.
Havent measure how much.

Make this thing go without seizeng first.

DEVCON has some epoxyputty wich I try for transfer roofs.

Btw June 1st, outside temp 4*c no rush to the sea!

[LittleCharger]

Yes , because I dont have .030 useable piston for white ph. Well I do have new set some wisecos and bored ph. Dont want to use it now. Saddly someone has has done some cleanup for it and made same error as I did, moved transfers up when smoothening them.
Havent measure how much.

Make this thing go without seizeng first.

DEVCON has some epoxyputty wich I try for transfer roofs.

Btw June 1st, outside temp 4*c no rush to the sea!

Yes you really need to understand what your doing when moving the transfers, a good block becomes scrap pretty quick. Generally just clean up on transfers. We use to turn in the 7's with a stock ported 56er with 160lbs compression with a nitro case and a 23 no problem, doesn't get much simpler then that.

Sounds like swimming weather at 4 degrees. We don't run a thermostat after break in but have to monitor heat in the block when testing in the spring due to cold water.