RedBarron55
Jet Boat Addict
- Messages
- 280
- Reaction score
- 100
- Points
- 122
- Location
- Navarre, FL
- Boat Make
- Jetcraft
- Year
- 1995
- Boat Model
- Other
- Boat Length
- 16
I had a problem with water getting into the cylinders of my 90 hp Mercury (Force) Sport Jet and I have found a few thinga out.
First there are two types of crankcases some with the cooling water inlet in the forward side of the exhaust cooling water chamber, This is not necessary since the water for cooling for the jet comes in the lower aft cooling water chamber. The presence of this hole means that there is a possible opening from that hole past the base gasket and into the bottom of the exhaust chamber. To make this problem worse you might have the wrong gasket that has an opening from this hole to that chamber
Right gasket
Wrong gasket
Note that the hole forward of the exhaust chamber is completely open in the wrong gasket as it is for the outboard version.
The gasket was appreciably thinner as well.
Personally I filled the hole in the bottom of the forward chamber with JB Weld so that if the gasket leaked it would be less likely to get into the cylinders.
Also my engine leaked water into the bilge from the adapter base and the gasket must have been leaking other places as well.
The O rings that seal from the adapter to the pump base might have been leaking as well.
I hope that this dries up the engine compartment and settles the problem with water in the wrong places in the engine and boat.
Step by step closer and closer I get.
Now after I test the engine again I have one question of just a small miss at max high RPM.
It seems that the timing changes a little while that is happening.
First there are two types of crankcases some with the cooling water inlet in the forward side of the exhaust cooling water chamber, This is not necessary since the water for cooling for the jet comes in the lower aft cooling water chamber. The presence of this hole means that there is a possible opening from that hole past the base gasket and into the bottom of the exhaust chamber. To make this problem worse you might have the wrong gasket that has an opening from this hole to that chamber
Right gasket
Wrong gasket
Note that the hole forward of the exhaust chamber is completely open in the wrong gasket as it is for the outboard version.
The gasket was appreciably thinner as well.
Personally I filled the hole in the bottom of the forward chamber with JB Weld so that if the gasket leaked it would be less likely to get into the cylinders.
Also my engine leaked water into the bilge from the adapter base and the gasket must have been leaking other places as well.
The O rings that seal from the adapter to the pump base might have been leaking as well.
I hope that this dries up the engine compartment and settles the problem with water in the wrong places in the engine and boat.
Step by step closer and closer I get.
Now after I test the engine again I have one question of just a small miss at max high RPM.
It seems that the timing changes a little while that is happening.
