Power into headwind

[barson]

Reading earlier posts on props and underpowered boats - then had first hand experience - coming back into harbour dead into a 10 gusting 20 knot westerley and outgoing tide and waves - and making about 1-2 knots - is no fun.

What I found curious is that my new 8hp Yanmar did so poorly (27ft long keel) into the chop. On reasonable seas does around 5 knots at 3,200 revs - into teh chop could hardly make 2200 revs.

If I understand previous posts right I shouldn't be surprised at the lack of performance - its basically an auxiliary - but should I have that sort of rev loss??? Won;t be out for a few weeks to see if an engine problem or the conditions, so wondering...

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[tugboat]

If you've been bumping about in wind-over-tide you may have stirred up some junk in the fuel tank. It would be worth checking your fuel filters to see if there is a partial obstruction. That would cause a reduction in fuel flow and a drop in revs.

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[snowleopard]

agreed - it's not the headwind if you're losing revs. if not a loss of power it could be something round the prop.

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[Birdseye]

Are you getting black smoke? The injection system is mechanically governed so at full throttle you are putting in the max fuel. But at 2200 revs you are not sucking in the corresponding air volume so you should be getting some black smoke. If you are not doing so, then is the throttle moving through the full range?

Tie up against a pontoon in still water and see what revs you can get. It will be less than you get when moving by a few hundred, but if you are still getting below 3000 then I reckon you have a mech problem - either extra drag in the transmission system (ie rope round prop etc) or something with the yanmar.


If you are getting over 3000 then this seems unlikely. You might be over propped of simply under powered.

My boat has 4 hp / tonne (the usual rule of thumb minimum these days) but into 20 kn headwind and a chop to go with it, I struggle to do more than 2 knots.

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.