Power loss while cruising

[Stevego]

Took the boat out for one last run yesterday. Noticed a few issues:
While cruising at say 20 to 30 MPH the boat will suddenly start to slow down as if the throttle was being slowed. Almost feels like it wants to stall. If I push on the throttle it speeds right back up. Has done this a few times during summer and seems worse once engine warm. Plenty of fuel in the tank and impeller was clear. Ideas??

My wear ring is a bit worn but the boat seems to cavitate ALOT more once warmed up. Upon leaving the dock at startup it pulls fine, once warmed up the cavitaion is worse. This could be just my perception.... Any reason why cavitation would occur more once warm? (No weeds in grate or impeller)

Compression checks at 130 and 135. Spark plugs are new.

Thanks

 

[Stevego]

Any ideas??? I will re-check compression this weekend while winterizing.

 

[djredman99]

Sounds like two separate issues.

Issue #1: With the details you are providing, I would start with changing you plugs. Your carbs may need cleaned/rebuilt/adjusted back to spec as well. Could be you are too rich/too lean in that 20-30 mph range. Could do a plug chop at that speed (run at ~25 mph for 30 seconds, kill engine at speed (don't slow down), pull plugs and read).

Issue #2: Check into your carbon ring. It could be slipping a bit or damaged and allowing more air to get sucked into your pump and giving you more cavitation, beyond what your worn wear ring is already causing. Do you have any water in hull?

EDIT: Just noticed you said plugs were new.

 

[Stevego]

Very little water in hull. Although you may be onto something with the Carbon ring. Could it cause cavitiation more once warmed up? Maybe it gets looser when hot?