volvo revs please....

[LeonF]

Replaced the two blader on my Volvo MD2010 at end of last year with a 3 blader, inch larger and degree more pitch. Great improvement...motored into 30 knot wind and slight tide effortlessly, especially compared to the hard slog it would have been with the previous one. Ran the engine in gear late last night, lashed to pontoon, finally afloat. At wide open throttle could get no more than 2000 revs. Boat surged nicely on warps, so I reckon she would have been going nicely, but should I worry ?? I recall Norris the prop people saying something about the engine not being able to reach higher revs beause it would be under greater load, but is this likely to be the cause? Manual states range of 3200-3500.
Have read previous posters replies re his 2020 dropping revs, and will try all solutions suggested, but perhaps I am worrying needlessly??
Thanks for any advice ....

 

[Swagman]

Also had a 2010 with a three bladed maxiprop on last yacht and max revs were circa 2,300 - most efficient was 2,000.
Sorry can't recall exact size - but it was not small.

IMHO your own analysis seems on track and if it were me, I would not worry.

JOHN

 

[boatmike]

Glad to hear it as I have one as a wing engine and have just replaced the awful 2 blade folding prop on the saildrive with an autoprop for the same reason but not launched yet. Don't worry about revs reached on a "bollard pull". If the prop is right you should reach 3200 with the throttle wide open when the boat is free to move .

 

[dickh]

To get maximum power the engine should reach at least 3200 revs. If it won't rev higher than this when under full load, not a bollard pull, you are overpropped and therefore not getting the best out of your engine.

 

[LeonF]

Thanks guys....but can you explain why the load on a 'bollard pull' is different to that when motoring free ? I remember when punching the head wind and tide last year that we were going very well.. at just under 2000 revs..

 

[fireball]

Ever tried pushing a car?
It is always hard to start it rolling, but once it is going it is much easier ...
Well - I think it will be along similar lines ...

 

[andy_wilson]

Bollard pull...

There is no flow due to the water moving past the hull.

Once the prop. is passing through the water at 6 knots the engine will rev higher.