I have a 1999 yamaha exciter 270hp jet boat. I'll start from the beginning. I bought it back in March. Ran great first few times out. Powerful take off and approx 55mph. Second outing I discovered my gas gauge was not working and ran out of gas. Luckily I have reserve. On the Next outting both motors would bogg down when i first started the engines. I would gouge on the thottles and it would clear up and run fine but it would do that everytime I stopped and cranked back up. I figured when I ran out of gas on the previous trip it got trash in the filter. I decided to take it to a mechanic to have carbs rebuild. After I got the boat back I took it out. It started up great whereas before i used to have to use starter fluid on the cold engine. However I noticed it didn't have the take off power it once had nor did it have the top end speed it once had. It now runs bout 40mph. It runs smooth though. I took it out one more time and same thing. Decided to check spark plugs. Port side engine front cylinder had chocolate brown spark plug, middle was almost black and back cylinder was SNOW white. Looked brand new. Starboard side they were all about the same with chocolate brown spark plug color, maybe a little darker. (attached pics of white one and one from other cylinder)
So I decided to check compression.
Port side
Front cylinder 115 psi
Middle 100psi
Back 100 psi (the one with the white plug)
Starboard side
Front cylinder 115 psi
Middle 110 psi
Back 113 psi
Also noticed a pool of oil in bottom of engine compartment, about a quart. The pool of oil has not gotten any bigger over time sitting in driveway and tank still full. Bought new oil lines to replace. Was about to do that when I noticed my plug. I know the oil was not there prior the my last outing.
If I remember correctly, the rpms on both engines were about 5500 after rebuild. Can't remember what they were before.
I have spark. As suggested by someone I took off flame arrestors, cranked and reved up engine to see if fuel was flowing. I only saw it flowing threw the back carb (the one with the white plug). On the starboard side I only saw it going threw the middle carb (the plug looked like the other one in the pics).
Took it to a jet ski mechanic this time. The other one that rebuild my carbs is more of an outboard motor guy. Anyway waiting on him to tell me what he found and what needs to be done. When I took it to him describing what I just said, he said he's almost sure its gonna need a top end rebuild from what I said (white plug, loss of power, and low rpms) but couldn't be for sure into he got into it.
Just trying to get some advice or suggestions on what it might be. I'm impatient waiting to hear from him and want to make sure he's gonna do me right.
So I decided to check compression.
Port side
Front cylinder 115 psi
Middle 100psi
Back 100 psi (the one with the white plug)
Starboard side
Front cylinder 115 psi
Middle 110 psi
Back 113 psi
Also noticed a pool of oil in bottom of engine compartment, about a quart. The pool of oil has not gotten any bigger over time sitting in driveway and tank still full. Bought new oil lines to replace. Was about to do that when I noticed my plug. I know the oil was not there prior the my last outing.
If I remember correctly, the rpms on both engines were about 5500 after rebuild. Can't remember what they were before.
I have spark. As suggested by someone I took off flame arrestors, cranked and reved up engine to see if fuel was flowing. I only saw it flowing threw the back carb (the one with the white plug). On the starboard side I only saw it going threw the middle carb (the plug looked like the other one in the pics).
Took it to a jet ski mechanic this time. The other one that rebuild my carbs is more of an outboard motor guy. Anyway waiting on him to tell me what he found and what needs to be done. When I took it to him describing what I just said, he said he's almost sure its gonna need a top end rebuild from what I said (white plug, loss of power, and low rpms) but couldn't be for sure into he got into it.
Just trying to get some advice or suggestions on what it might be. I'm impatient waiting to hear from him and want to make sure he's gonna do me right.
