Engine problems

[DavidWR]

I have a Mercruiser 5.0 MPI engine in my Bayliner 265. Both boat and engine are 12 months old, serviced 7 months ago. Up until last weekend it would happily do 30kts no problem.

On Tuesday I took her out only to find that the engine would not rev above about 3000 rpm and the boat would not go above 10kts.

There are no other symptoms, cooling is fine, oil pressure and levels are fine, plenty of fuel, the throttle is fully opening as I've checked. The engine starts first time every time, and is perfectly smooth until about 3k when it just will not go faster. There is no misfiring or lumpy running. The props are both fine as I've checked.

Does anyone have any ideas as I'm running out of them!?

Thanks,

Dave.

 

[Nautorius]

Do not know much about engines,

However have you checked your hull for fouling. This could well be an issue. Is your boat antifouled? If she is when was she last scrubbed? You may also have crustacians all over your outdrive as well!

Cheers

Paul

 

[LeytonC]

Does it rev ok out of gear?

 

[DavidWR]

Thanks. If the hull is the problem then I've had a massive build up over only 4 days so I don't think it's that.

When it's out of gear it revs up to about 3500 rpm when the warning buzzer comes on telling me I'm revving it too high out of gear.

Thanks again for any ideas.

 

[mikemcgregor]

does it have a turbo? blades of the turbo could be jammed.

 

[Nauti Fox]

Check the fuel filter, I had a 7.4 and when it had water in the fuel filter it lost all the top end but ran alright lower down, although mine had a carb it may still have the same effect with yours... maybe.

 

[Chris_d]

Sounds like the ECU has gone into some kind of limp home mode, you should be able to rev to the red line out of gear, check all the sensor connections on the engine something might have just fell off. Have a browse of some of the American sites there maybe a way to reset the ECU or determine which sensor has failed.

Alternatively you may just have blocked fuel filter or faulty pump.

 

[Its_Only_Money]

Mpi engines from various makes often limit the rev range to something in the 2500-3000rpm (varies by make/model but shouls be a particular figure noted in the manual), if the engine thinks it is overheating or has some other fault, if it seems the engine will not rev past 3000rpm whatever (in/out of gear etc), then the ECU may think it has a problem - even if it hasn't if you see what I mean.

 

[LeytonC]

Would be my next stop - if it revs ok out of gear, check your filters or general fuel quality.

 

[DavidWR]

Thanks. There is no turbo, but the fuel filter suggestion is a possibility. Also this happened (it seems) the day after a very heavy downpour overnight, so water could be the issue. Any other suggestions welcome thanks.

 

[atlowers]

Not a new possibility but suffered the same symptoms and it turned out to be loads of muck in the filter. The boat had been laid up for 12 months and it would appear that folowing 5 hours of running on delivery home trip, the fuel level had got low and some sludge which had settled in the bottom of the tanks had been raked up and clogged the filter resulting in your exact symptoms. Changed the filter and she was fine. Good luck and hope its easily rectified.

 

[chuckaduck]

try the ignition timing if retarded will do this try advancing a bit and see

 

[dt1]

should still do more than 10knts at 3000rpm,,just a thought ,the props not slipping on the bush is it

 

[DavidWR]

Thanks to all who replied. It has been diagnosed as a faulty ECU unit - fortunately covered under warranty. Just have to get hold of the replacement now.