Fishwater2002
Active Member
- Messages
- 30
- Reaction score
- 12
- Points
- 27
- Boat Make
- Yamaha
- Year
- 2004
- Boat Model
- SX
- Boat Length
- 23
So I recently bought a boat with some known issues, originally I was under the impression that there was an impeller problem & cavitation. See my earlier thread for the whole story
https://jetboaters.net/threads/buying-a-used-boat-with-a-cavitation-issue.42250/
It ends up that after a ton of great suggestions here that there wasn’t an issue with the impeller & that I should reseal a few areas. After doing so & replacing the plugs we finally had time to take the boat out to test. Prior to testing I replaced all 8 spark plugs, both #3 plugs were rusty & looked terrible. I did a compression test & all the cylinders except for both #3 plugs wires exactly 151psi across the board with the exception of both #3 cylinders which were exactly at 125psi, my assumption is that there may have been some rust on the valve seats causing the valves to hang slightly open. Fuel was supposedly treated but I topped off with fresh super unleaded & added 60ozs of Sea Foam to treat the fuel. I purchased YDS & checked for codes, sure enough the starboard side had codes stored from when the original owner injected a piece of wood, approximately 3 hours prior to my ownership. Other than that everything looked good. While going over the boat I noticed that the starboard side motor was idling around 1200 RPM so I turned the throttle screw up to get the engine idling around 1900 RPM like the port side.
Finally got the boat in yesterday & at first ran great, hopped up on plane with no issues. Maxed out at 10k RPM & cruised around at varying RPM’s testing & trying to burn the fuel out. After a half hour or so I started to notice the starboard engine dropping RPM’s, just slightly & intermittently at first but then the tach started jumping from 7,000 RPM’s down to 5,000 then eventually it stalled. Trying to restart it with no luck we started to limp home on the port engine, after a few minutes the starboard restarted & worked fine but then eventually as I cruised in at 7,000 RPM’s it started cutting out again with the needle bouncing between 5-7,000 until I was in the no wake zone. So here I am now after pulling the boat for the day wondering what my next step is & asking for help. I’m thinking possibly ignition related or electronic since it got worse once it was warmed up?![PXL_20230810_132730115_Original.jpeg PXL_20230810_132730115_Original.jpeg](https://jetboaters.nyc3.digitaloceanspaces.com/data/attachments/206/206955-2aedefa9c422594163d326174a026184.jpg?hash=Ku3vqcQiWU)
![PXL_20230810_143634662.PORTRAIT_Original.jpeg PXL_20230810_143634662.PORTRAIT_Original.jpeg](https://jetboaters.nyc3.digitaloceanspaces.com/data/attachments/206/206957-82cc74177ef82e5e44425466549ef844.jpg?hash=gsx0F374Ll)
https://jetboaters.net/threads/buying-a-used-boat-with-a-cavitation-issue.42250/
It ends up that after a ton of great suggestions here that there wasn’t an issue with the impeller & that I should reseal a few areas. After doing so & replacing the plugs we finally had time to take the boat out to test. Prior to testing I replaced all 8 spark plugs, both #3 plugs were rusty & looked terrible. I did a compression test & all the cylinders except for both #3 plugs wires exactly 151psi across the board with the exception of both #3 cylinders which were exactly at 125psi, my assumption is that there may have been some rust on the valve seats causing the valves to hang slightly open. Fuel was supposedly treated but I topped off with fresh super unleaded & added 60ozs of Sea Foam to treat the fuel. I purchased YDS & checked for codes, sure enough the starboard side had codes stored from when the original owner injected a piece of wood, approximately 3 hours prior to my ownership. Other than that everything looked good. While going over the boat I noticed that the starboard side motor was idling around 1200 RPM so I turned the throttle screw up to get the engine idling around 1900 RPM like the port side.
Finally got the boat in yesterday & at first ran great, hopped up on plane with no issues. Maxed out at 10k RPM & cruised around at varying RPM’s testing & trying to burn the fuel out. After a half hour or so I started to notice the starboard engine dropping RPM’s, just slightly & intermittently at first but then the tach started jumping from 7,000 RPM’s down to 5,000 then eventually it stalled. Trying to restart it with no luck we started to limp home on the port engine, after a few minutes the starboard restarted & worked fine but then eventually as I cruised in at 7,000 RPM’s it started cutting out again with the needle bouncing between 5-7,000 until I was in the no wake zone. So here I am now after pulling the boat for the day wondering what my next step is & asking for help. I’m thinking possibly ignition related or electronic since it got worse once it was warmed up?
![PXL_20230810_132730115_Original.jpeg PXL_20230810_132730115_Original.jpeg](https://jetboaters.nyc3.digitaloceanspaces.com/data/attachments/206/206955-2aedefa9c422594163d326174a026184.jpg?hash=Ku3vqcQiWU)
![PXL_20230810_143634662.PORTRAIT_Original.jpeg PXL_20230810_143634662.PORTRAIT_Original.jpeg](https://jetboaters.nyc3.digitaloceanspaces.com/data/attachments/206/206957-82cc74177ef82e5e44425466549ef844.jpg?hash=gsx0F374Ll)