1966 Johnson 20HP

[Old Crow]

I removed the power head and when performing a pressure test I get air leaking out of the water passages. The exhaust and head gaskets look good. I"m concernd I may have a crack cylinder or head even though I don't notice anything. How would be a good way to test where the air is coming from?<br />Thanks

 

[OBJ]

Re: 1966 Johnson 20HP

Welcome Old Crow!<br /><br />I would ask what kind of pressure test are you doing and where (how) are you applying air pressure. How much pressure are you using?

 

[Paul Moir]

Re: 1966 Johnson 20HP

Welcome to Iboats!<br />That would be most rare for one of those engines. By far the head gasket is the most common source. What are you pressurizing, the cylinders/crankcase or the water jacket?<br /><br />EDIT: Daing it OBJ, you're beating me on all these posts tonight!

 

[Old Crow]

Re: 1966 Johnson 20HP

I've removed the power head and then blocked off the exhaust. I made a flange that attached to the intake and hooked up an air hose to it. This should pressurize the intake, cylinders, and exhaust system, correct. When doing so I get air out the water passages. I've only turned air pressure up to 5-10 psi.<br />Thanks,

 

[Old Crow]

Re: 1966 Johnson 20HP

TTT

 

[OBJ]

Re: 1966 Johnson 20HP

CAN'T remember if the exhaust cover has two covers, an "inner" exhaust cover and an outter cover.....but if it does, you could have air press getting under the inner cover and into the outter cover cavity which is all water. Could be getting out that way. Maybe Paul can shed some light on it.<br /><br />I don't type any faster Paul......maybe I just read quickerer.....

 

[Old Crow]

Re: 1966 Johnson 20HP

I took the out cover off and resealed the inner cover back on but still have the same results.

 

[Old Crow]

Re: 1966 Johnson 20HP

I want to pull the crank case in half. What is holding the mag on? How do you get it off. Thanks

 

[Paul Moir]

Re: 1966 Johnson 20HP

The magneto? The four phillips screws near the crankshaft. Lift the entire magneto off then remove the brass ring beneath. I'm assuming you have the flywheel off. Do you?<br /><br />The alignment pins that align the crank cases are tapered and must be driven out the 'right' way.<br /><br />Any hope of blocking off the cooling passages at the bottom of the block, filling the block via the thermostat, and applying a vaccuum? It's a bit of a job, but it will pin-point your leak.

 

[Old Crow]

Re: 1966 Johnson 20HP

Anyone know where I can find on line the bolt torque limits for this engine?

 

[Paul Moir]

Re: 1966 Johnson 20HP

What do you mean by "bolt torque limits"? Do you mean how much you can torque a bolt until it snaps, or are you looking for the torque specs? If you're looking for the torque specs, what do you need the torque specs to (ie, head, flywheel, etc)?

 

[Old Crow]

Re: 1966 Johnson 20HP

Specs, I stand corrected.<br />Head bolts and Crankcase bolts most importantly, Flywheel nut would help.

 

[itstippy]

Re: 1966 Johnson 20HP

POWER HEAD IN/LB FT/LB<br />Flywheel 480-540 40-45<br />Con rods 180-186 15-15.5<br />Head bolts 96-120 8-10<br />Crankcase upper 110-130 9-10<br />Crankcase center120-130 10-11<br />Crankcase lower 110-130 9-10<br />Starter 96-120 8-10<br />Spark plugs 240-246 20-20.5

 

[Old Crow]

Re: 1966 Johnson 20HP

After splitting the crankcase I noticed there is no oring around the upper crankshaft bearing To seal between the bearing and crankcase (there is one on the bottom bearing). Is this normal?<br /><br />When I did a pressure test I could hear air leaking from under the flywheel.<br /><br />There is a hose that runs from the lower bearing to the upper also internal porting from the upper bearing to the intake. <br />I'm thinking this is how they get oil to the upper bearing. It's actually sucked from the lower bearing and deposited at the upper.

 

[Old Crow]

Re: 1966 Johnson 20HP

TTT

 

[Paul Moir]

Re: 1966 Johnson 20HP

No, I'm almost certain there should be no o-ring on the top main bearing of that engine. There should be one on the bottom main bearing. I have no idea why the 22.0 CID block was built that way, as there's o-rings on the bigger blocks' top main bearings.<br />That hose is indeed for oil recirculation, although I'm not certain of exactly how it works as there is no check valve like on modern outboards.

 

[Old Crow]

Re: 1966 Johnson 20HP

Thank You