Looking for a little help. Short story is I had a alarm go off this past weekend on a 2005 525 EFI w approx 160 hours. Motor was running great prior to alarm and during. No reduction of power and running smooth. 5 beep alarm. Scanned the motor and had 3 fault codes that I need help with. #77 cam sensor, 17 idle map str, and 21 ect overHT. My question is, should I simply replace all three or is there a sequence I should try so as not to buy unneeded parts (the damn cam sensor is very expensive, $700 ish). Also, any issue with using a ac delco cam sensor that is much less expensive. Any help would be appreciated. Thanks in advance.

Based on my experience with my 525's...
Did the alarm go off at higher rpm or as you were coming off plane/idle, say less then 2,000rpm. If off plane or idle, replace the MAP sensor. also, do not throttle down at a rapid pace because that will cause a map code. I doubt it is the cam sensor.

It happened after running. I had come off plane and was idling under a bridge when the alarm started. I appreciate the feedback. Thx

Joe your boat looks fantastic