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I have owned twin 2004 225hp DI's since new in 2004. They are on a 2004 CapeHorn27. I had approx 1600 hours on them pretty much flawless until last year when I blew cylinder 4 in my starboard due to detonation. I heard it pretty much only during the high torque rpm's about 3500 coming up on plane and it was very loud. Once it became obvious that it was time I removed the head and found the piston top degraded down to the rings. I have no clue how this engine ran like that but it shows how strong these engines were. Local machine shop who resleeved said his opinion was lack of lubrication so I replaced the enitire oil ***sembly/hoses/fuel to oil check valve/all recirc oil fittings. I also sent injector 4 to DFI technoligies and had it rebuilt. I rebuilt the engine and the sound came right back (loud rattling at same rpm's of 3500) and I was back to square 1. Pulled off head and found both cylinder 4 and 6 locator pins on pistons (Top pin) had discharged allowing the rings to rotate and break off, I had used WSM kit for rebuild. Now I purchased a used block that had 130 psi in every cylinder (Confirmed myself at first start up) so I ruled the block itself out as the cause this time. I also exchanged all 6 injectors and the EMM with the other motor (Starboard EMM and injectors went to the port engine and vise versa). I figured if it was the computer or injectors the issue would follow. All injectors were placed in proper cylinders so no need for programming. I ran her up tp 3500rpm's and still clear as day detonation in starboard motor. So its not the injectors/EMM/Oil sytem/ or block itself, new thermostats (Updated ones that run hotter) with the new style spark plugs, rebuilt blow off valves, new water pumps. I then swapped fuel manifolds to see if maybe lines had a clog but issue stayed with the starboard motor. I am willing to swap part by part until the isuue moves to the port engine and then can be identified. My main question here is can an electrical issue be the culprit or is it most likely a lean fuel condition? can it be the coil that operates cylinders 4 and 6? I dont lose power when running so I would think electrical would be ruled out. Can a bad PDP cause detonation? What the heck could be causing it? Fuel is fresh 89 octane. Same props have been on the engines since new and in perfect condition. Nothing heavy has added weight to the boat either. No codes were activated at anytime in the engine either. Thanks for the help, Dave
Update:I noticed that there is a large amount of bubbles coming up from around the engine (water turbulence) at idle suggesting an exhaust leak somewhere in the mid section. Other engine does not have this so all exhaust is coming out properly through propellor hub, could it be possible that there is an exhaust hole in the midsection causing the hot gases to build up and not exit properly and keeping the exhaust gases in the cylinder therefore causing the detonation?
Update:I noticed that there is a large amount of bubbles coming up from around the engine (water turbulence) at idle suggesting an exhaust leak somewhere in the mid section. Other engine does not have this so all exhaust is coming out properly through propellor hub, could it be possible that there is an exhaust hole in the midsection causing the hot gases to build up and not exit properly and keeping the exhaust gases in the cylinder therefore causing the detonation?
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