History - 2002 Crusader 8.1 mpi std on 39 silverton MY. Had a number of problems with port engine in past subject of posts in 2011 with ultimate fix being replacement of ECM on port engine. Only about 300 hours on engines as I only go out a couple times a year and run in Lake Erie. When first purchased boat WOT under load was about 4400rpm with cruising speed at 3600 rpm and about 24mph. SOG.
In 2016 boat ran fine except it maxes out at full throttle on both engines at only 3400 rpm and 20 mph while running. (On a three hour run I was able to get up to 22.9 SOG and 3600 rpm.) In neutral engines will rev to about 4400.(As a side note and as posted in other threads the port tach is inop because the tach driver on the ECM is bad.) Starboard engine is original equipment, while port has had new ECM, fuel pumps, fuel filters, etc as a result of stalling problems. Mechanic at shop says probably just algae build up on bottom but sounds fishy to me. All fuel from local marina and all gas in tanks from 2016. At end of season I had the marina mechanic put diagnostics on the engines and he couldn’t find anything unusual indicating no codes, fuel pressure, etc was normal and rpm’s were consistent with reading on starboard tach. (I am not a mechanic so taking him at his word). I did replace plugs in both engines as well as pancake fuel filters and filters in FCC. None of the filters were significantly dirty. Pick up tube was clean and anti siphon checked.
Now the real kicker, took boat out over fourth of July, 2017 on flat lake and engine only reached 3400rpm and 15 mph SOG. (Did have 13 people on board). HELP, only things left I can think of from reading other posts is to replace the ECM on port engine again, the throttle sensor, or have fuel injectors checked. One other possibility – I know prop shafts have never been cleaned with slight grime build up. Bottom gets cleaned yearly and painted(last 2014) but not sure about the prop shaft
In 2016 boat ran fine except it maxes out at full throttle on both engines at only 3400 rpm and 20 mph while running. (On a three hour run I was able to get up to 22.9 SOG and 3600 rpm.) In neutral engines will rev to about 4400.(As a side note and as posted in other threads the port tach is inop because the tach driver on the ECM is bad.) Starboard engine is original equipment, while port has had new ECM, fuel pumps, fuel filters, etc as a result of stalling problems. Mechanic at shop says probably just algae build up on bottom but sounds fishy to me. All fuel from local marina and all gas in tanks from 2016. At end of season I had the marina mechanic put diagnostics on the engines and he couldn’t find anything unusual indicating no codes, fuel pressure, etc was normal and rpm’s were consistent with reading on starboard tach. (I am not a mechanic so taking him at his word). I did replace plugs in both engines as well as pancake fuel filters and filters in FCC. None of the filters were significantly dirty. Pick up tube was clean and anti siphon checked.
Now the real kicker, took boat out over fourth of July, 2017 on flat lake and engine only reached 3400rpm and 15 mph SOG. (Did have 13 people on board). HELP, only things left I can think of from reading other posts is to replace the ECM on port engine again, the throttle sensor, or have fuel injectors checked. One other possibility – I know prop shafts have never been cleaned with slight grime build up. Bottom gets cleaned yearly and painted(last 2014) but not sure about the prop shaft
