I am looking for some advice and any help would be much appreciated. I have a 2012 Supreme v226 with an Indmar 6.0L, 420HP that I purchased last summer and have been having some issues with it since I got it.
I bought the boat to be used solely for wakesurfing and after spending a little time dialing in a wake I have been running anywhere from 3000-3500 lbs of ballast weight. With this much weight I noticed that it was taking a little longer to get up to speed (10.8-11.4 mph) while pulling a surfer. I then did some research on props, talked to the folks at Acme and found that with the amount of weight that I am running a prop upgrade seemed to be the answer. So, I upgraded my prop from an Acme 537 to an Acme 1273. I notice an immediate change in low end power and it seemed to be the answer.
Soon there after I started having issues with my service required alarm going off, the culprit for the alarm was O2 sensors throwing alarm codes. After having the sensors changed out the boat seemed to be back to running normally. We took the boat loaded it up with ballast and surfed for about 2.5 hrs and everything appeared normal. While dumping the fat sacs I picked up on a rubber buring odor and opened the engine compartment to find the exhaust manifolds running extremely hot, that they were burning the rubber hoses attached to the them. About that same time my alarm went off, but at no time registered a hot engine temp (over 160 deg) I took the boat back to the shop, discovered the code was another O2 sensor and ended up having to get the manifolds, catalysts, O2 sensors, rubber exhaust hoses replaced.
Fast forward 1 week later, I took the boat out with my mechanic and loaded up ballast like I would surfing. We then accelerated at WOT and were only able to get a maximum of 3200 RPM and it would begin cavitating shortly thereafter, the manufacturer says normal operating RPM's are 5200-5600.
I have many questions, but my main one is can overpropping cause such an extreme lugging and drop in RPM's? Can this be the cause of all my problems and if so what prop would be recommended? A loss of 2000 RPM's below the maufacturers recommended amount seems very drastic to me, could something else be at play here? This was Acme's prop recommendation given the ballast weight that I would be running. Also, the boat has no problem getting to the recommended RPM's without the weight and I live at about 500' above sea level so altitude is not a factor. Any help or advice is needed and would be greatly appreciated.