SportJet 120XR2 water in crank housing

[X-17]

Last autumn when laying up I connected a hose to the water inlet and flushed the engine for 10 minutes. Today, upon removing reed housings and carbs for check and overhaul I found a lot of water (like several decilitres) in the bottom of the crank housing.

The engine ran ok although not giving the expected speed when taken out of the water last autumn. It has spent all of its life in salt water.

Where is the most likely leak? And how can it have such a bad leak and still run? There is a mysterious exhaust leak somewhere too, I suspect the two are connected.

 

[X-17]

Ran a compression test yesterday. All cylinders beyween 10 and 12 bar, but I belive 1 bar between lowest and highest is max even for teo stroke engines? The cylinder with 10 bar is the cylinder where there is slight surface rust on the plug and on the counterweights on the crankshaft.

Question is can I get as much as 10 bar if head gasket is gone to extent that lots of water leaks into the cylinder?

 

[RedBarron55]

Often there is a leak in the base gasket that lets water get into the exhaust and fill up to the exhaust port on the lower cylinder. You should use a low water pressure and running the engine is a good idea as well.
Did you use the customer flush that goes to the top of the engine or the dealer service adapter that goes to the hose that runs around the engine to the exhaust manifold?
The compression has nothing to do with the water getting into the cylinder and depending on the position of the piston could also run into the crank through the transfer port and intake port.
Next time run the engine and use fogging spray to put the engine to bed.
If you operate in fresh water the flush is not as necessary, but salt water should probably be flushed after each use.
Low water flow and pressure, watch the temp gauge and after starting the water, start the engine (only with the dealer service adapter, not the customer flush line. Do not run the engine on the customer flush hose)

 

[X-17]

The no 2 cyl from top is squeeky clean, I have a leak at bottom of the head gasket. So the lowish compression on that cylinder is confirmed.

When you say base gasket, I am unsure what you mean?

I used a dealer adapter.

 

[RedBarron55]

By base gasket I mean the gasket the is between the bottom of the block and the adapter base that bolts to the pump.

 

[X-17]

Ah thanks, is there a diagram anywhere on the net showing the cooling flow? I have searched in vain, and nothing in the service manual either.

 

[X-17]

Considering I have an exhaust leak into the engine room, is it more likely the gasket to the exhaust manifold is leaking, allowing water into the exhaust and into the engine block when engine is not running?

 

[RedBarron55]

Probably not a leak from the exhaust gasket and head.
But fix it and see if that fixes your problem.
But the cooling circuit is from the pump (dealer service adapter) through the hose to the lower aft exhaust manifold.
Then it fills the exhaust water jacket and passes from the top of the exhaust to the head and down and back up to the thermostat. From there it runs down to the exhaust box and out the ride plate with the exhaust.
The outboard cooling comes from the foot pump up to the port on the adapter plate and through that 3/4" hole into the exhaust jacket like the jet, but, and this is a big but, the gasket seals the outboard and the jet differently. It is easy for the passage from that 3/4" hole to leak under the adapter to the stuffing box at the bottom of the exhaust area, filling it with water.
With the engine running the back pressure helps slow the leak and the cylinder exhaust ports blow themselves clear as well.

 

[X-17]

Exhaust manifold is proving troblesome. Two of the long bolts snapped at the head. The rest came out fine. But the manifold sits like it is welded to the block. I suspect it is corroded together with the block where there might be a gap in the gasket e g around bolt holes. And stuck like fused to the gasket.

What are my options? I suspect a blowtorch along the edge at the gasket plus brute force may be the only one?

I have an induction heater so getting the broken bolts out once the manifold is off is not too much of a problem.

 

[RedBarron55]

Perhaps a good solid whack with a mallet

 

[X-17]

Spraying corrosion eater in bolt holes and gasketvremover around the edga. Blowtorch on the manifold along the edge toward the block. Many very solid whacks with a (very) heavy hammer did not help at all. Next up, sledgehammer?

 

[X-17]

I finally got all the nuts holding the power head to the pump adapter plate. And having lifted the power head I ended up giving the manifold enough whacks to strip the thread in the block holding the two broken bolts. Just drill and tap one size up, no problem. I have used heat, sulphuric acid and penetrating mix of acetone and ATF to free the remains out of the manifold. One bolt out, one to go. By the signs of it the leak was beween manifold and block, just where the two stuck bolts are. A leak there would of course reach the bolts and corrode them stuck in the manifold. Makes sense to me.

 

[X-17]

Everything went back together nicely. Problem solved, it now runs as it should and water stsys where it should.