Down in revs

[Budgie]

I have a Moody 40 with Volvo MD22 (50hp) and saildrive with 2 bladed folding prop. When I bought the boat 3 years ago I found that full throttle gave 3000 rpm. I set myself a personal max of 2500 and generally cruise at around 2000 to 2200. I recently tried full throttle again but only got around 2650 rpm. Boat speed was marginally down. Sailing speeds seem OK.

The engine runs sweetly, and the rpm have been checked as correct. The boat was antifouled in March, and the prop and saildrive were treated with MPX. The last bit of throttle movement has no effect on rpm. In neutral 3200 rpm can be achieved (I think this is the governed figure).

Before I have a diver check my prop does anyone have any ideas?

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[DepSol]

Check throttle adjusters and adjust as required or check filters.
Also check fouling as it could be mucky.

<hr width=100% size=1>Dom

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

 

[Budgie]

Thanks for that. I have checked that the throttle valve is opening fully, and am about to check the filters. I have been told that fuel starvation will cause irregular running at high rpm, and I don't have that problem.

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[dickh]

Re: Down in revs/Filter Micron ratings?

Definately check your fuel filters, my Perkins would not run above 2100 under load recently,(although I have religiously changed them both at layup time) I changed both filters and now back up to over 3000 rpm. Interestingly, I cut open the filters and only the Primary filter had any muck in it.
I'm now trying to find out the Micron Ratings of fuel filters; this information is very hard to obtain! Ideally I would like to use a 20 or 30 micron on the prefilter and a 5 micron filter on the engine. I suspect both my filters were 5 micron.


<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[vyv_cox]

Re: Down in revs/Filter Micron ratings?

Stick with the 5 micron. Filters are intended to clog up, so it achieved its purpose. I can't see any sense in deliberately allowing dirt to pass the filter to save changing it so frequently. It's doing its job, protecting your expensive fuel system.

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[John7]

Re: Down in revs/Filter Micron ratings?

A more likly problem is fouling. I went in in March and had to scrub the bottem, mild fouling and really clean the prop in July as it was bad. Full spead with both engin and boat again now.

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[beneteau_305_553]

Try adding STP fuel injector cleaner to the fuel.

Dirty injectors reduce the power output significantly and I have found this additive really does work.

Its available at car accessory outlets. About £5 per bottle and should be added to fuel injected cars either petrol or diesel every 10,000 miles.



<hr width=100% size=1>Richard

 

[DepSol]

No good if the filters are blocked, you need something that unblocks filters aswell as cleans the injectors /forums/images/icons/smile.gif

<hr width=100% size=1>Dom

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