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Cruising speed

Posted: Tue Sep 09, 2008 5:29 pm
by Cat Tales
Anyone know the cruise speed & max speed under power and what the burn rates are of the 29hp Yanmars. Even though these are all sailboats, we know how much we end up motoring. We are not financially ready, but I'm arming myself (in preparation of my wife's objections) with info for when we have the ability to upgrade to a larger boat.

Thanks,
Chris

Re: Cruising speed

Posted: Wed Sep 10, 2008 8:05 am
by Tanah-Keeta
I don't know what the fuel burn rate is but I was surprised to learn from several owners that the max speed under power is not much more than the 36 with outboards.

Re: Cruising speed

Posted: Wed Sep 10, 2008 8:46 am
by duetto
hi,

try going to http://www.mastry.com. they have data sheets on most engine models which contain fuel consumption curves. you'll need to know knots vs rpms.

Re: Cruising speed

Posted: Sun Sep 28, 2008 6:58 pm
by barefeet
Hi. I have a PDQ 44 with Yanmar 3gm30 engines. They are just a couple of HP less than the current version - so fuel curves should be similar. We cruise with one engine at full power at about 6.5 knots in calm conditions. With 2 Engines we can bring that speed up to 8 knots (8.5 with a clean bottom!). Obviously, two engines doubles your fuel usage but does not double you speed ... so one engine is more efficient use of power at high rev's.

If we run at a conservative speed we can get more than 900 miles of range out of 120 gallons of diesel - that drops to around 400 miles with both engines at full speed. As you can see from the fuel curve below, one engine at 2400 rpm is probably the most efficient way to go ... but it is a bit slow.

One engine fuel curve ...
RPM Speed (calm) Fuel
2400 4.5 .5 Gph
2750 5 .79 Gph
3000 5.5 1.05 Gph
3200 6 1.34
3400 6.5 1.71 Gph

Hope this helps.