Another Weird One for Me

raybo3

This could only happen to me. I am driving my boat and get an alarm. Lower the RPM's on my port engine and the alarm goes away but comes right back as soon as I go over 3000. This happened the last 2 times out.  Bring it to the marine mechanic and he puts the computer on it and no codes. Takes it for a ride and no alarm. WTF why can it never be easy..LOL

LaRea

Sounds like a restriction in the sea water intake system, but why are some faults not "sticky" and a reader can't see them?  

raybo3

Temp, oil pressure and voltage all perfect.

YYZRC

Those water pressure sensors suck. Try swapping them and see if the beeps move to starboard. 

raybo3

Yeah that's what I am thinking. The sensor is only a year old and it's OEM

LaRea

raybo3 said:

Temp, oil pressure and voltage all perfect.

The temp gauge is reading coolant temperature.  But if there's not enough raw water flow, you can get an EMCT (exhaust manifold coolant temp) alarm -- even when the coolant temp is within spec.  (That's on a 496, and I think the 350 is the same.)

Dream_Inn

I agree, definitely water pressure sensors.  Are your exhaust manifolds old?  I had this issue at the beginning of the season.  The alarm will go when water pressure is over 40psi, which is at higher rpms.  For me, I was due to change my exhaust manifolds.

raybo3

My manifolds are 3 years old. I don't think my boat went into limp mode with the pressure sensor last year, just the alarm. 

Handymans342

Just get rid of the boat Ray and all your troubles wash away. Besides the weather up there is horrible

raybo3

Update: So it appears that I get all the weird problems. Here is what he found. Oil pressure gauge works perfect on the dash however the (alarm) wires that run to the computer are basically rotted and corroded away. So the computer see's 42 psi but that stays steady on the computer and does not go up with higher rpm's so it sounds the alarm. The real strange part is that it does not send a code......... 

halifax212

Good find. That doesn't sound like too bad a fix.

raybo3

halifax212 said:

Good find. That doesn't sound like too bad a fix.

I will let you know once I get the bill......lol Yes it was a good find by him. He actually swapped computers from one side to the other to see if the problem would follow and thats when he noticed the pressure was steady on the "bad" side. 

Michael T

I spoke with the owner of the company that imports water pressure sensors for Mercruiser (posted this to the forum back in 2016 or so) and, if I remember correctly he said something like when made in the U.S. the failure rate for these sensors was less than 5% , when it went to Mexico it was 25%, then when it went to Indonesia it was 75% (or higher). He said it was still cheaper to import them even with a failure rate like that. When I said said what about the owner aggravation, lost time and costs spent trouble shooting, he replied, well, there's that! Some Canadian companies - a high end bicycle manufacturer (Argon 18) had a 2 page spread in the Business section of Toronto's Globe and Mail - are bringing all parts manufacturing back home as people are sick and tired of crappy foreign parts and will pay more for something that actually works and lasts.