175 Johnson crankcase leak

ditchdigger1

Cadet
Joined
Jul 19, 2005
Messages
20
I had the powerhead rebuilt two months ago ( 89 175 johnson ) and I'm still breaking it in. I have only ran one tank through with double oil and just started the second. I had every cylinder bored 20 over and all new bearings and seals replaced. The problem I'm having is that yesterday it was hard to start and I noticed that the crankcase where the two halves join had a small leak. The fuel pump surges like it is sucking air about every 2 to 3 seconds, would the crankcase seal cause this? Other than this it runs fine.
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: 175 Johnson crankcase leak

Is the oil coming from the mating line black and gooey? If so, it's just exhaust oil. Running double oil will cause more unburned oil to shoot through to the exhaust. If eventually migrates down. Now if it's clear oil, then that's a different matter.<br /><br />If the engine is surging, check out your fuel line connections. May be sucking a bit of air. Are you running with a VRO pump?
 

R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: 175 Johnson crankcase leak

If you had the engine done at a shop, The mechanic that did the work is not going to be happy to see that. The only way that I have seen to correct this problem is to split the halves, clean, and reseal. It has to be corrected, That would give one, possibly two cylinders a lean condition.
 

ditchdigger1

Cadet
Joined
Jul 19, 2005
Messages
20
Re: 175 Johnson crankcase leak

The mechanic built the rotating assembly and I built the rest, because of how far behind he was. His work should be under warranty. It looks like he used some type of sealer on the split case, I did on the other gaskets. The oil seems to be fresh where it's leaking. Would it be taking in air there causing the pump to surge, like it is loosing vacuum? I plugged the VRO off and replaced all of the gas lines.
 

clanton

Rear Admiral
Joined
Jul 9, 2001
Messages
4,876
Re: 175 Johnson crankcase leak

Yes, and that cylinder will run lean.
 

ditchdigger1

Cadet
Joined
Jul 19, 2005
Messages
20
Re: 175 Johnson crankcase leak

I told the mechanic the pump didn't surge like that before the powerhead was rebuilt, but he told me the pump was bad. Are you sure the case leak would cause the pump to surge?
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: 175 Johnson crankcase leak

Whoops....thought he was talking about the mating line at the gear case and midsection....my bad! Too early in the morning.... :)
 

clanton

Rear Admiral
Joined
Jul 9, 2001
Messages
4,876
Re: 175 Johnson crankcase leak

Does not matter where it makes the pump surge or not (probley does), and depends which cylinder is leaking. The engine will still run lean on the cylinders that are leaking which= burnt piston.
 

ditchdigger1

Cadet
Joined
Jul 19, 2005
Messages
20
Re: 175 Johnson crankcase leak

I was told that I could loosen the case bolts and should be able to seperate the case just enough to apply some aviation gasket sealer and retighten the bolts. Anyone think this could be done without tearing the motor down? After it's fixed can I spray premix or powertuner on the case to check for leaks?
 

R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: 175 Johnson crankcase leak

That won't work! Don't even try. How are you going to even slightly seperate the case halves when they are locked in place by the top, and bottom crankshaft bearing carriers. Those case halves have to come apart, cleaned, and resealed. Read the service manual on cleaning, and sealing crankcase halves. If you could even slightly seperate the case halves, you would break the seal all around, then you would have a real leak.
 

ditchdigger1

Cadet
Joined
Jul 19, 2005
Messages
20
Re: 175 Johnson crankcase leak

I found that the leak was coming from the inspection plates and not the case. I also had trouble with it starting. The mechanic told me that the starter was bad, something about it pulling too many amps? When I got it home I hooked a battery charger up and it started fine. Will the battery cause it to not start if the battery is only 3/4 charged? It had set up about 3 to 4 weeks since I last started it.
 

R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: 175 Johnson crankcase leak

The starter has to supply enough cranking speed for the magneto CD to work. Thats a good deal that the leak was'nt between the case halves.
 
Top