Is this an exhaust leak?

New to me 140 in my sig. It has a lot of junk built up on the outside of the exhaust housing. This was accompanied by black goo in the transom of the boat it came off of. I assumed the mess in the transom was gunked up water leaking out when the motor was tilted all the way up for transit. There is no junk in the bottom of the inside of the cowl.

I have not run the motor other than for a short time so I have not looked for a leak. I'm hesitant to run it much until I go through the carbs as this motor sat for several months and it does not run "right" on the muffs. My main question is if this is a leak can I replace the gaskets on the inner housings without pulling the power head. It would seem I could get at it all with the gear case removed but wanted to know for sure. I'm ordering a water pump and carb kits and was going to buy the three exhaust housing gaskets as well but if I need to pull the power head I'm going to need more gaskets.

This may or may not be your problem, BUT it is a semi common problem...........

In looking at the top motor mount bolt area, it appears that the gasket that the powerhead sits upon (powerhead to adapter plate) has blow thru between the exhaust chamber area and the top motor mount area. Unfortunately the only way to tell for sure is to remove the powerhead.

If this is the case, hopefully only the gasket is involved. If either the powerhead or adapter plate area has lost any of its sealing area, that would bring into play having a machine shop heli-arc the area(s).

I dug into it a bit today. Attached is a picture with a cover removed. Looks like a power head to adapter leak to me. It's not easy to see and referencing the parts breakdown is only partially helpful but it appears that I'll need the gasket #37 for the area I noted gasket and the other area is sealed with RTV as noted? There is no gasket for that listed and looking at it with as little as I have exposed it's not clear what the RTV is sealing.

I've got all winter to get this sorted but I'd like to get into it sooner rather than later so I have time to get anything else fixed. I guess if the PH is coming off I should probably do the thermostat at the same time. Anything else, "While I'm in there"?

I have no idea why RTV is in that area. I've never used in at all in my 30+ years with OMC.

I recommend using regular gasket sealer on that powerhead to adapter plate gasket. Sealer that comes in a can that has a brush attached to its screw off cap.

Will do!! I normally use RTV as gasket sealer but unlike most folks never use a bead. I always spread it out in a thin layer, mate the parts and torque it down. This method has served me well in the automotive world but I certainly defer to the experts advice with this.

Going to be a good learning experience. I've ordered the gaskets and all the associated parts for the thermostats. Not sure if I need the relief valves and springs but it's cheap and well worth the piece of mind. Same deal with the water pump. It works now but for 75 bucks it's well worth knowing exactly what I have and how it's put together.

Not sure what it would cost to have all this work done but it's 200 bucks in parts and 0 labor so it seems like a bargain.

Thanks!

Before you start spending $$$ on parts it would be wise to determine the overall health of the motor.------I know you heard it run , but that means very little.--------Perhaps a compression test and an inspection of the pistons and rings is in order.--------Removal of the bypass covers ( 6 screws for each cover ) and you can look at the rings on the intake sides of the pistons.

racerone said:

Before you start spending $$$ on parts it would be wise to determine the overall health of the motor.------I know you heard it run , but that means very little.--------Perhaps a compression test and an inspection of the pistons and rings is in order.--------Removal of the bypass covers ( 6 screws for each cover ) and you can look at the rings on the intake sides of the pistons.

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Yep, Should have explained it all. I did a compression check prior to purchase. All four cylinders were 110-115. It ran ok on the muffs but not great. It starts very easily but does not idle nor free rev as good as it should. According to the seller the motor was ran a few times earlier this year and than has sat for about four months. That leads me to believe the carbs are gummed up.

From my experience with the 70 I know that all the little adjustments add up to make a big difference in how the motor runs so I'm pretty sure it just needs gone though. I'm comfortable with the compression readings and it did not knock or make any weird noises so I'm thinking I'm good to go. That said I'll pull the exhaust cover and take a look.

ship wreck said:

That said I'll pull the exhaust cover and take a look.

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Correction bypass covers. I really should read more carefully.