loss of engine power

[BigLes]

Went for a nice sail today (wasn't it warm!), and on the way back up Chichester Harbour, under power the engine revs started to drop to just under 2000 rpm. Even applying more throttle the engine wouldn't rev any higher and the boat slowed to 2.5 knots. Tried the engine out of gear and it revs fine, however in either forward or reverse (ie under load) it hardly gives any power. It's a Volvo 2002.

Possible causes?:

1) Fouled prop.

2) Head gasket failing - noticed film of oil on the water where cooling water is coming out of the exhaust, and oil level down (full at start of season, less than 40 hours running and oil is at bottom of level marker on dipstick)

3) Bug in fuel causing fuel feed blockage.

As we are planning to go away on the boat a week tomorrow has anyone any ideas so I can get the problem resolved quickly?

Thanks

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[Rick]

If it happened all of a sudden, then 1 seems a likely culprit. What was the colour of the exhaust under load?

Has engine previously used oil? And are you sure the oil in the exhaust wasn't unburnt fuel oil?

I'd be inclined for starters to dive and clean the prop, replace the fuel filters, and see if the problem persists. If prop clean and filter change fixes, how hard is it to drain and flush your fuel tank?


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[DepSol]

Why drain the tank? Double dose of Soltron if there is muck in there and off you go.

Would have thought it was possibly one of the other items on the list, but if in dobt and with such a short time left b4 you go it wouldnt hurt to eliminate as much as possible.

Quick swim will sort out if one is a problem or not, No.2 is the wort scenario and No.3 easily fixed as above.

<hr width=100% size=1>Dom

<A target="_blank" HREF=http://www.soltron.co.uk>the website</A>

 

[MarkJohnson]

Sounds like diesel starvation to me.

Whilst it could be any of the other causes, diesel engines are so simple, look for the obvious first.

Mj

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[BigLes]

I've since had a 'read-up' and it could be fuel starvation. We had run out of fuel the previous time out (motor sailing and the boat heeled, the fuel in the tank obviously sluiced to one side, the opposite side to the feed pipe and the engine petered out). Have since re-fueled and bled the system, however I only bled the fuel filter on the front of th engine. I have since read about bleeding the primary fuel filter near the fuel tank. I'm going to re-bleed the whole system. The puzzling thing is the film of oil showing from the exhaust. Could this be unburnt fuel? There is no smoke coming from the exhaust.

Also thinking about it the oil level was last taken before the boat was launched, so she may not have been standing level. A top-up of oil will also be made, plus of course a look at the prop.

I'm praying it's not scenario 2!

Thanks for comments so far.

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[longjohnsilver]

Don't worry about the film of oil in the exhaust, that's quite normal for many engines. I'd also discount the head gasket as being the problem, you'll almost certainly see overheating and water in the oil and /or oil in the fresh water (header tank) before seeing any loss of power.

I would put my money on a blocked fuel filter having had the same symptoms myself on many occasions. Change the filter(s), add soltron and all should be well.

If you have something around the prop I'd also expect some vibration which you don't mention.

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[BigLes]

I wouldn't say there was vibration as such but the endgine did feel a little 'lumpy'.

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[Rich_F]

I had a similar problem earlier this year (also a Penta 2002), and it was solved by bleeding the secondary fuel filter, which seemed to be full of air.

It seemed that when I had fitted the filter (weeks previously) I must have trapped a large air bubble in the filter, as it had been very quick to bleed the fuel through. When the engine started having problems, the bleeding process took much longer than when orginally fitting the filter!

Rich

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[Cantata]

Yes, always check the obvious first before fearing the worst. I would bet you've got air in the system.

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[AndrewB]

Scenario 2

Doesn't sound like this. Unless the blowout is major (oil spraying out from under the head, caused most likely by serious overheating), then usually the power loss is fairly slight. If you think oil is getting in the water, then almost certainly the reverse would be happening, is the engine oil emulsified pale grey?

In any case getting a head gasket changed isn't that big a deal, so long as the head itself isn't damaged.

I agree with most other suggestions here. Another possible cause might be water in the fuel tanks or filters, tends to get shaken up into the fuel when the boat is used and so the symptoms appear after you've been sailing awhile.

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[Trevor_swfyc]

I agree with Rich if it isn't a fouled prop, then it is most likely air in the secondary filter. Either fill the diesel tank so that the diesel head is higher than any bleed valve or use the manual lift on the pump. You should have two or maybe three bleed points start from the primary filter - coalescer working you way up to the injectors.

Hope this cures it!
Trevor

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[HappyandBroke]

Ive got exactly the same problem on my engine at the moment, mines a Penta 2003. Just changed the filter and hopefully this will sort it out. I think its unlikely the prop is overfouled as we can turn the shaft easily by hand.

On my engine its revs fine out of gear, but in gear there appears to be no increase in revs once the throttle gets past the half way position.

The water seperator seems fine but we drained it anyway and the filters been changed even though it was new at the start of the season. Ive also tried bleeding it too.

Let me know if you find out the problem and Ill do the same.

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[BigLes]

Sorted!

Bled the fuel system, starting with the primary filter (the one with the glass bowl), then the secondary filter (on the front of the engine) and then at the injectors (just to be sure) using the lever on the fuel pump. Also checked both filters to make sure they were clean (they were) and all is fine now. It was air locked in the fuel feed system - I obviously hadn't bled it properly when we ran out of fuel!.

Thanks to everyone for the guidance.

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[longjohnsilver]

Glad it was something simple, much easier than a head gasket!!

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[brianhumber]

Re: Yep, Always check the easy things first

First lesson of engineering is keep it simple and always do the simple checks first.
I suppose my my embarassing error in not doing this was not checking the secondary filters on the way back from the Falkland Islands. Could not understand why No1 cylinder was 5% down on power so assumed the overhauled valves were faulty (sometimes you had a dud set of re-conditioned nozzles) so stopped and changed the fuel valves twice over the next few days. Still no improvement and much hair pulling ensued until I happened to turn the knife edge secondary filter handles on the middle plates and heard the engine note change slightly - sure enough power restored, higher exhaust and turbo temps on the front three. Much leg pulling substituted for hair pulling - turned out the MOD 'heavy oil' was a right old mismatch of varying oils totally different to the normal very heavy fuel oil we normally bunkered with and was prone to gumming up the secondary filters

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[jac]

Re: Scenario 2

I agree with this.

I also have a 2002. we were getting no power at all in gear but revved fine out of gear. water seperator almost full.

Drained the tank - changed filters, bled and runs ok.

also taught me to ALWAYS run the engine under load whilst boat still firmly attached to something.

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