mercury 25 hp jet

i just bought a 15 ft. jon boat with a mercury 25 hp jet 4 stroke outboard. i have been using this extensively on the river and it seems i lose jet stream power after i sucked up some debris. the last time this happened, the secondary **** outlet stopped streaming water. i took it in to the repair shop and they cleared it out and changed the impeller. i just sucked up some rocks and debris last week. the boat speed went from 18 mph to 13 mph. the secondary **** outlet is still working and i don't see any impediment in the jet intake or outtake. i really don't want to take it back to repair shop as that last experience cost me $300 bucks. any ideas on what is wrong and course of action would be greatly appreciated. thanks.

Re: mercury 25 hp jet

Look in the nozzle where the water comes out of the jet, there is an inside tube, this where the exhaust comes out, the space around that tube is where the water comes out. If a small rock passes through the pump it may get stuck in this passage way. Use a screw driver to pry it out, or push it back into the pump, it will typically drop through the pump and onto the ground. You may also have something stuck in the intake grate, that's easy to check too. If you don't see anything stuck in either end of the pump try it on the water again, frequently small rocks and things will fall out once the motor is turned off or on the way home on the trailer.

Worst case you can take the shoe off (lower section where intake is located). It should have 6 or 8 bolts, remove them and it will drop down, this will give you a good view of the impeller. You won't normally see anything stuck in there, but it's possible. You will be able to inspect the impeller though.

Re: mercury 25 hp jet

i removed the inside tube and it was clear. also nothing stuck in water intake housing. there were rocks but i removed them. is it possible that debris is in the impeller higher up and i can't see it? thanks.

ondarvr said:

Look in the nozzle where the water comes out of the jet, there is an inside tube, this where the exhaust comes out, the space around that tube is where the water comes out. If a small rock passes through the pump it may get stuck in this passage way. Use a screw driver to pry it out, or push it back into the pump, it will typically drop through the pump and onto the ground. You may also have something stuck in the intake grate, that's easy to check too. If you don't see anything stuck in either end of the pump try it on the water again, frequently small rocks and things will fall out once the motor is turned off or on the way home on the trailer.

Worst case you can take the shoe off (lower section where intake is located). It should have 6 or 8 bolts, remove them and it will drop down, this will give you a good view of the impeller. You won't normally see anything stuck in there, but it's possible. You will be able to inspect the impeller though.

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Re: mercury 25 hp jet

It's the outside passage way around the tube that needs to be clear.

It is possible for a rock or wood to get stuck in the impeller, but it doesn't happen very often, when you take the shoe off you can look into it and see everythnig.