Misfire/Depth Finder

D

Depth Sea

New Member
Jul 26, 2021
12
Boat Info
SEARAY 210 SLX
Engines
5.O MPI MERCRUISER ALPHA
Searay 210 Select, 2010
5.0 MPI Mercruiser
After service: New Distributor Cap, Rotor, Hull Sensor and new coil.
With 10 min into the water and at idle speed an alarm came on and a message on the dash that said " Fault, Misfire, action display slow down", the alarm kept going every 60 sec approximate.
Spoke with the mechanic, said had to change spark plugs and plug wires. If this does not fix it , we have to continue looking deep into the engine.
I brought the boat back to the water to confirm the problem, noticed the depth finder was not working (not in the display), now there is no more alarm the boat started perfect....
A week after took it out again, once again after 30 minutes the alarm started. Now where I used to see the depth finder I have a fault message.
Turned the boat off, waited about 30 minutes, restarted and once again the alarm is gone no message, but depth finder is gone as well.
I am not sure about the misfire and if the issue with the Depth finder is related to the fault (misfire). Now looks like there 2 problems.
Any comments will be appreciated.
 
what was the most recent work you had done on the boat and why does the tech hate you?
 
Depth Sea said:
Searay 210 Select, 2010
5.0 MPI Mercruiser
After service: New Distributor Cap, Rotor, Hull Sensor and new coil.
With 10 min into the water and at idle speed an alarm came on and a message on the dash that said " Fault, Misfire, action display slow down", the alarm kept going every 60 sec approximate.
Spoke with the mechanic, said had to change spark plugs and plug wires. If this does not fix it , we have to continue looking deep into the engine.
I brought the boat back to the water to confirm the problem, noticed the depth finder was not working (not in the display), now there is no more alarm the boat started perfect....
A week after took it out again, once again after 30 minutes the alarm started. Now where I used to see the depth finder I have a fault message.
Turned the boat off, waited about 30 minutes, restarted and once again the alarm is gone no message, but depth finder is gone as well.
I am not sure about the misfire and if the issue with the Depth finder is related to the fault (misfire). Now looks like there 2 problems.
Any comments will be appreciated.
Click to expand...
Did you have any issues before the service? How many hours on the motor? 5.0/5.7 motors are generally easy on the plugs and they can last 300 hours or more.

The misfire could be a loose spark plug wire.



A ticking sound may be heard if there is a loose plug wire. If you run the motor in the dark, you may even see the spark if that is indeed the issue.
 
Auto/truck distributor rebld kit contains screws with wrong pitch which don't fully seat although tightened. Erratic performance is the result. Please don't overtighten the wrong screws, get the right ones. I had saved the old ones and have my own tube of Lok-tite, luckily.
 
Arminius said:
what was the most recent work you had done on the boat and why does the tech hate you?
Click to expand...

New Distributor Cap, Rotor, Hull Sensor and new coil. I don't think he hates me!!! ajjaj
Thank you for your respond.
 
Last edited:
Espos4 said:
Did you have any issues before the service? How many hours on the motor? 5.0/5.7 motors are generally easy on the plugs and they can last 300 hours or more.

The misfire could be a loose spark plug wire.



A ticking sound may be heard if there is a loose plug wire. If you run the motor in the dark, you may even see the spark if that is indeed the issue.
Click to expand...
Thank you,
It is 302 hrs, per the maintenance papers received with the boat they change plugs 80 hrs about ago. I think will be a good idea to install new ones.
I forgot to add that when purchased it was 263 hrs.
I will review all wires, no ticking sound
 
Arminius said:
Auto/truck distributor rebld kit contains screws with wrong pitch which don't fully seat although tightened. Erratic performance is the result. Please don't overtighten the wrong screws, get the right ones. I had saved the old ones and have my own tube of Lok-tite, luckily.
Click to expand...
Thank you,
 
I will work on the plugs and wires this weekend. Hope is juts that.
 
I think it was the 2 torx screws that hold the cap on that won't seat if they came form the auto store vs boat store. Just grab the cap and pull. If it wiggles, that's the problem.
 
Arminius said:
I think it was the 2 torx screws that hold the cap on that won't seat if they came form the auto store vs boat store. Just grab the cap and pull. If it wiggles, that's the problem.
Click to expand...
Thank you I will check that, was told that there is a $40 neutral sensor that also displays the same error. will see.
 
Check the cap is ok, wire ok, and plugs look ok.
I believe is something else, the motor hesitate on neutral at cold start. Then triggers the Misfire. If start with a little of throttle works fins and once it is warm works fine except again in neutral it does not hold 600 to 700 rpms, does go up and down and it can stall.
 
put the old parts back. If they are trashed, replace each individual part again starting with the most complex.
 
The idle problem could be idle air control valve (IAC). Lots of posts on here where they cause starting and idle issues when they fail.
 
ColoSR said:
The idle problem could be idle air control valve (IAC). Lots of posts on here where they cause starting and idle issues when they fail.
Click to expand...
Sounds exactly as the condition I have. Read an watch a couple of videos so I will chnage the IAC.
Thank you
 
Let us know if it works!
 
ColoSR said:
Let us know if it works!
Click to expand...
Sorry for a late response. Installed IAC yesterday all looked OK, took the boat to the water today for a test. The boat did not started. Engine turns, fuel pump works. Need to start again.
 
Thank you all, after final inspection. The fuel pump was not give the correct pressure was 21 PSI and it should be 43 aprox. Unfortunate is the service center the one in charge of this repair and it will be a bit expensive. We are waiting for parts.
 
I am not up on your MPI but auto port injection of that vintage puts limited reliance on the pump for pressure. I heard Mercruiser had 2 systems. For cars, a high pressure pump buried in tank would produce 70 psi or something and then a pressure relief valve on engine would divert everything over 60 or so back to tank. This produced constant pressure at injectors regardless of rpm. Which is all to say, You can't work on these engines yourself. First step with a MPI is diagnosis with a Mercruiser box that costs $500 +. There is no OBD2 port. I say this having believed I could fix anything but eventually realizing it is no longer true-if it ever was.
 
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