Cyclone S jet boat need help

[bear47]

So I have a 1996 cyclone s jet boat with a 120 XR mercruiser in it replace the head gasket cuz I was getting water in the number four cylinder that didn't fix the problem so replace the exhaust side and that didn't fix the problem still getting water in the number four cylinder can anybody help me out with this where I could be getting water coming in from somewhere else

 

[bear47]

Stuck need help

 

[alldodge]

This being a Mercury sport jet I moved it to the Mercury/Mercruiser section. It will get more views.

Never messed with one. I'm looking at the parts and not seeing anything that would tell me what might be the issue. Intake area maybe?

 

[stresspoint]

might be time to pressure test the engine block with it all bolted together.
possible corrosion issue.

 

[bear47]

might be time to pressure test the engine block with it all bolted together.
possible corrosion issue.

Everything's back together and torque properly out of the water runs perfectly smooth no rough idle nothing put in the water will not start sucks water into the number four

 

[bear47]

This being a Mercury sport jet I moved it to the Mercury/Mercruiser section. It will get more views.

Never messed with one. I'm looking at the parts and not seeing anything that would tell me what might be the issue. Intake area maybe?

Thanks for moving it I wasn't for sure where to put it first time on here I have read a few forums before on here that's why I decided to sign up I work on a lot of boats and some questions there is iffy

 

[bear47]

Everything's back together and torque properly out of the water runs perfectly smooth no rough idle nothing put in the water will not start sucks water into the number four

And my compressions over 120 so I think compression is fine somebody was telling me there's a exhaust gasket or exhaust plate below the power head where it mounts to the jet I don't know how true that is but if somebody could help me with that that'd be great

 

[stresspoint]

And my compressions over 120 so I think compression is fine somebody was telling me there's a exhaust gasket or exhaust plate below the power head where it mounts to the jet I don't know how true that is but if somebody could help me with that that'd be great

you should get away with just pressurizing that one cylinder ,IE doing a leak down test.
if you have a scope ?, bring the piston up to just above the ports lock it there with a wedge in the FW so the motor cant turn over, test there , that should rule out head or gasket , which would bring to an intake or exhaust problem.
intake would be my guess .

 

[nola mike]

Does this have a 3.0 mercruiser, or is this one of the jet boats with the Force outboard powerhead? (And some had merc outboards too I believe).

 

[bear47]

might be time to pressure test the engine block with it all bolted together.
possible corrosion issue.

might be time to pressure test the engine block with it all bolted together.
possible corrosion issue.

you should get away with just pressurizing that one cylinder ,IE doing a leak down test.
if you have a scope ?, bring the piston up to just above the ports lock it there with a wedge in the FW so the motor cant turn over, test there , that should rule out head or gasket , which would bring to an intake or exhaust problem.
intake would be my guess .

I'm thinking intake for I have just put new head and exhaust gaskets and motor runs out of the water so is the intake the gasket on the bottom of the power head?? More familiar with outboards first inboard jet boat

 

[bear47]

I'm thinking intake for I have just put new head and exhaust gaskets and motor runs out of the water so is the intake the gasket on the bottom of the power head?? More familiar with outboards first inboard jet boat

Plus had exhaust and head off pistons and rings all look good and clean no scoring.

 

[bear47]

Does this have a 3.0 mercruiser, or is this one of the jet boats with the Force outboard powerhead? (And some had merc outboards too I believe).

Has the 120xr merc jet boat

 

[nola mike]

Has the 120xr merc jet boat

so @alldodge maybe the merc outboard section?

 

[alldodge]

so @alldodge maybe the merc outboard section?

It's one of those that isn't an OB or Inboard this is why I put it here. If another Mod want's to move it elsewhere I'm ok

 

[dubs283]

Should create a new forum for all the L drive folks seeking advice. Would fit nicely there

 

[Bondo]

It's one of those that isn't an OB or Inboard this is why I put it here. If another Mod want's to move it elsewhere I'm ok

Ayuh,..... I usually put such things in the jetski forum, especially for motor problems,.....

 

[alldodge]

Ayuh,..... I usually put such things in the jetski forum, especially for motor problems,.....

Maybe we should discuss in Mod section becuase it was there and no one mentioned anything. Got some notice here. What about other jet drives?

 

[dubs283]

What about other jet drives?

Lake lice?

 

[bear47]

Does this have a 3.0 mercruiser, or is this one of the jet boats with the Force outboard powerhead? (And some had merc outboards too I believe).

Yes merc 120xr inboard jet boat

 

[H20Rat]

Rule number 1 of the small sportjets is NEVER, ever run them on a hose or dry. Exhaust gases build up, ignite, and pop the ride plate gasket out. This in turn causes a big leak that can kill performance, but worse case can suck water back into the engine. Sounds very much like what is happening to you.

Crawl under with a bright flashlight and check the gasket.

And for the mods discussing, its been a while, but IIRC the 120 sportjets were entirely merc designed outboard powerheads mated to a jet drive. The 90/95hp's were branded merc but were a Frankenstein mix of Force and merc parts. For the most part the outboard guys are probably going to be the most knowledgeable, although those boats are becoming pretty rare. (esp the 90/95/120 SJ') They don't have commonality with PWC's.