Edge70

Found this gray wire not connected to anything and looking like it's been burned off. My boat also won't run as it goes into guardian mode with a solid horn when trying to take off. Could these be related? Where is the gray wire for the Tach supposed to go. It looks intact from the wiring harness but I need to terminate it somewhere. Please advise.

AllDodge

iTrader: (1)

Its probably the Auxiliary Tach connector. The Tach connects to the PCM and splice off to connect to a handheld or other if needed.

Edge70

@AllDodge, yes, I think you are right. May actually be a butt splice not a broken wire. Will have to investigate the solid horn more.

AllDodge

iTrader: (1)

A constant alarm would be, ECT overheat, low drive lube, low oil pressure, low sea water pump pressure

The sea water pump pressure happens most often

Edge70

Normally when this has happened in the past, it's low drive lube. I always keep a bottle in the boat with me. I've ensure that's topped right up but still getting the horn. Engine oil is good with good pressure on the guages. I can feel the exhaust headers getting water staying pretty cool to the touch but maybe that's not the best way to determine if it's getting adequate water cooling from the sea water pump. I'll have to see if I can get it scanned I guess. Boat was running fine at the end of the season last year.... this happened on the first launch the other day. Late start this year

AllDodge

iTrader: (1)

The drive lube bottle switch can go bad. Disconnect one of the leads to see if the alarm stops

The water pressure switches are the worst thing Merc ever installed in the motors. They go bad often and there expensive. That said if its the water sensor it would not sound when the motor is ON but not running

Edge70

I removed the lead to the lube bottle and horn still sounds. The engine will start fine and not alarm until I put it in gear and run the rpms up to 1000 or thereabouts. Then it will give a solid alarm. Exhaust headers still appear to be cool at this point when it happens. I can replicate this with the boat on my lift but lowered into the water by disengaging the drive and running the engine rpm's up. Seems like quite the rabbit hole without having a scanner to see the actual pressures and codes it's throwing.

Edge70

AllDodge bought a scanner and scanned the boat. Getting a low block pressure error reading which triggers the solid horn. Boat has 185 hours on it so thinking it might be time to change water pump. Has never been changed but I do change the impeller every other year. Last year I was getting this error as well but only when pushing the boat faster than 40 mph. Had them change it when they winterized it but now I get the error almost immediately... around 1100 rpm. Any thoughts?

AllDodge

iTrader: (1)

Most likely its the sensor and not the pump. Could remove the sensor and install a Tee then connect a gauge. Would get 2 to 4 psi at idle, and 20 to 30 from cruise to WOT

underpsi68

I'm not saying this is the issue, but the factory brass sea water pump housings are notorious for getting scored on the ends of the impeller. A lot of times when the impeller is changed you get low water pressure because the old impeller was worn into the grooves and had good suction. Test for pressure.

If a new housing is needed the Hardin stainless pump is a great replacement.