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Mercruiser 4.3 MPi 220hp power loss

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Karnic

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I have a nov 2006 Mercruiser 4.3mpi v6 engine that I have owned and serviced from new. The engine has covered around 600 hours and been used on a 23' Karnic 2260 walkaround with an alfa gen11 stern drive.

Plugs were changed Oct 2013 together with oils and filters, First trip out this year was yesterday after standing since Oct 2013. All went well from an engine point of view and cruised around 3 hours at 3000 rpm faultlessly.

Today I start up and travel out of marina to open channel at tickover. However upon acceleration to planing the engine lost power and started to misfire if over throttled. I stopped the engine and restarted and it ran great without any load on. When drive is engaged at tickover and up to 1500rpm the engine runs normally. to get onto the plane this boat requires 3000 rpm and at this point the engine cuts the power and goes into what I guess is 'Limp' mode. once in limp mode it will not increase the revs until the engine is stopped and restarted again.

I know this boat and engine as I carry out all my own maintenance, however maybe I will need to take it to a mercruiser dealer to diagnose, unless anyone can offer any help.

NOTE
The dash board Temperature gauge has failed during the winter storage and is reading hot, even when the engine is cold, although this did not affect the performance of the engine on yesterdays 3 hour cruise.

Please help if you can. Thank you.
 
If the ECU gets its temp reading from the same sensor as the gauge it may be the problem. Disconnect the gauge sender wire and ground it w/ignition switch in run position. If the gauge pegs or reads the max hot temp the gauge is good...sender is defective.
 
guyjg said:
If the ECU gets its temp reading from the same sensor as the gauge it may be the problem. Disconnect the gauge sender wire and ground it w/ignition switch in run position. If the gauge pegs or reads the max hot temp the gauge is good...sender is defective.
Click to expand...

Thank you I will investigate and report.
 
Karnic said:
I have a nov 2006 Mercruiser 4.3mpi v6 engine that I have owned and serviced from new. The engine has covered around 600 hours and been used on a 23' Karnic 2260 walkaround with an alfa gen11 stern drive.

Plugs were changed Oct 2013 together with oils and filters, First trip out this year was yesterday after standing since Oct 2013. All went well from an engine point of view and cruised around 3 hours at 3000 rpm faultlessly.

Today I start up and travel out of marina to open channel at tickover. However upon acceleration to planing the engine lost power and started to misfire if over throttled. I stopped the engine and restarted and it ran great without any load on. When drive is engaged at tickover and up to 1500rpm the engine runs normally. to get onto the plane this boat requires 3000 rpm and at this point the engine cuts the power and goes into what I guess is 'Limp' mode. once in limp mode it will not increase the revs until the engine is stopped and restarted again.

I know this boat and engine as I carry out all my own maintenance, however maybe I will need to take it to a mercruiser dealer to diagnose, unless anyone can offer any help.

NOTE
The dash board Temperature gauge has failed during the winter storage and is reading hot, even when the engine is cold, although this did not affect the performance of the engine on yesterdays 3 hour cruise.

Please help if you can. Thank you.
Click to expand...


Well, an interesting 5 days of checking and waiting for parts and more checking. I gave up the guess work and purchased an hour on a mercruiser laptop.

This identified 383.9 hours covered and a mix of confused faults 0.7hrs ago.
Cleared the previous faults, and ran the engine up under load until it entered safe mode, only to discover the battery was receiving 16.8volts.

I changed the alternator, as I had a spare, and 'way to go' she's back purring like a kitten at 3000rpm.

I hope this is helpful to anyone else experiencing power loss problems.

Closed.
 
Good!
But your engine should be reaching between 4200-4600rpms at wide open throttle (WOT), or it might be overpropped causing it to be lugging! (overworking).
 
MikDee said:
Good!
But your engine should be reaching between 4200-4600rpms at wide open throttle (WOT), or it might be overpropped causing it to be lugging! (overworking).
Click to expand...

Im not sure why you chose to add your comment mike but thank you, I don't feel the need to open my engine up to its maximum revs unnecessarily when fuel is costing up £6.50 per gallon. As it happens this particular rig runs great with a 19" prop when towing and achieves 4400 rpm with the 23" prop when cruising long range.

Thank you again
 
Just Checking, Then apparently you're propped right, and all is well with your engine. Reaching the propper rpm at WOT, means your engine is not lugging at any speed, then you're good to run at any speed you choose!
 
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