Originally Posted by JimN
You need a new mechanic. If he remembers anything from MC training, the first step, which he did, is verify the complaint. The second is 'do a visual inspection, including a wiggle test of the wiring'. Third, do the proper diagnostics, including connection to a diagnostic computer. Fourth, verify that the problem has been corrected.
Since "80% of all driveability issues are fuel related", he needs to check the fuel pressure, not just replace parts. His inability to correctly diagnose this problem shouldn't cost you money. Next, he needs to look at the data, especially where the ECM indicates whether the motor has overheated. An overheat is one of the only reasons the ECM goes into RPM reduction and if it has registered an overheat, the impeller and raw water cooling system need to be inspected. If they didn't replace the impeller in the time you have owned this boat, you need to talk to the service manager about this.
If the impeller is missing vanes, there's no way they replaced it, either last fall or this spring, so they should make whatever repairs are necessary, on their dime.
The mechanic should learn to diagnose these systems on some other boat, not yours. If he doesn't know how to look for the cause of the problems, it will be very apparent, very soon. He'll use the "shotgun method" of diagnosis, replacing part after part, until he finally "finds it", only by coincidence.
He needs to start by collecting the data and checking the raw water cooling system. If that reveals nothing, the ECT (Engine Coolant Temperature) sensor needs to be checked, along with the wires to the ECM (if the sensor proved bad, the wires are a moot point). If that doesn't show anything, and either the visual inspection or data should have let him know if the block grounds are clean, tight and working, THEN he needs to check the harness.
The diagnostic computer is only a tool but it can save a lot of time if the tech knows how to interpret the data. If he doesn't and just scratches his head, he needs more training before being let loose on these boats.
Yes, I'm being harsh but I have absolutely no tolerance for people replacing parts as a method of diagnosis. They should only be changed after proving faulty and you said nothing about a fuel pressure test, him taking a fuel sample or doing the normal diagnostics. How much gas is in the tank? If it's less than 1/2 full, top it off and see if the problem suddenly "vanishes". If it does, it's dirty gas and a clogged filter. Since the pump has already been replaced, I suspect dirty gas if topping it off fixes it, or bad raw water intake causing an actual overheat. If it's an indicated overheat and the raw water intake if good, the thermostat may be sticking closed or the ECT may be bad and these are easily checked.
Is, or has, this boat run in salt/brackish water with a fresh water cooling system? If so, has it been thoroughly inspected for the effects of the salt/brackish water?