Idle speed

Sep 6, 2011
435
How fast does your boat go forward at idle speed? I'm looking for speed not taking current or tide into account.

I'm shopping for props and they recommend larger than what I have which seems excessive.

My boat does 3-3.2 knots at idle and I have no idea if that is normal.

SC
 
Jan 12, 2011
930
Hunter 410 full time cruiser
I assume you mean with the transmission in gear otherwise my boat at idle doesn't move forward. If in gear it mainly just turns in clockwise circles due to prop walk once in forward at "idle".
 
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
How fast does your boat go forward at idle speed? I'm looking for speed not taking current or tide into account.

I'm shopping for props and they recommend larger than what I have which seems excessive.

My boat does 3-3.2 knots at idle and I have no idea if that is normal.

SC
When coming into the dock, it moves too fast... but never fast enough when i want to motor somewhere.

3 knots is about right on a calm flat water day... it really doesnt take much to move a sailboat at half of its hull speed as it is designed with minimum drag in mind...

When motoring in to the dock or tight quarters, you need to use the neutral position a lot so you can coast... then a bit of foreward to push, then coast again...
The prop should be sized for use to maintain the proper rpm at the top end of the engine performance, NEVER for speed or rpm at idle..
 
Jan 25, 2011
2,437
S2 11.0A Anacortes, WA
That seems a bit fast. I think were only around 2or a little less. WOT the boat will do 7.2 assuming clean bottom etc. we might be out next week. Ill test it.
 

Blitz

.
Jul 10, 2007
709
Seidelmann 34 Atlantic Highlands, NJ
idle spped vs. RPM

Maybe your engine idle is also set too high - what are your RPMs at idle; not in gear and in gear?:confused:
 
Sep 6, 2011
435
Maybe your engine idle is also set too high - what are your RPMs at idle; not in gear and in gear?:confused:
The boat is still on the hard but if memory serves at neutral it's maybe 5-600 and drops a bit in gear. Right now I have a big 15x13 prop which one manufacturer says is too small. My top rpm is 2500 so I cruise around 15-1600. At higher than that it starts smoking pretty good so I thought it was over propped. It always smokes a bit being a Volvo but at wot it's ridiculous.
SC
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
The boat is still on the hard but if memory serves at neutral it's maybe 5-600 and drops a bit in gear. Right now I have a big 15x13 prop which one manufacturer says is too small. My top rpm is 2500 so I cruise around 15-1600. At higher than that it starts smoking pretty good so I thought it was over propped. It always smokes a bit being a Volvo but at wot it's ridiculous.
SC
what size boat do you have and engine

use this to get it very close to what you should be useing

http://www.vicprop.com/displacement_size.php
 
Last edited:
Jan 25, 2011
2,437
S2 11.0A Anacortes, WA
You should come up with a 16 x 9. Mine according to survey is a 16x12. Three blade
 
Sep 6, 2011
435
You should come up with a 16 x 9. Mine according to survey is a 16x12. Three blade
Correct. The one prop manufacturer suggests 16x21 which seems excessive but is a feathering prop so not sure that makes a difference. I'm waiting to hear from the other. On the upside the one above is adjustable.

I don't own a laser tach but can check around. I'm sure someone I know has one. It wouldn't surprise me if things are off after 34 years.

SC
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Idle speed not a good test. See how many max RPM you can get in neutral/per mfg figure. Then in gear, moving, can you reach that same RPM? You should. If not, then your prop is off.
 

Blitz

.
Jul 10, 2007
709
Seidelmann 34 Atlantic Highlands, NJ
The boat is still on the hard but if memory serves at neutral it's maybe 5-600 and drops a bit in gear.
Not sure if this will help but it sounds like your Tach is off - idle speed for most Yanmars are 850-950 RPMs, looking up your Volvo (MD17C) it should be 750-810 RPMs.

As others have said, use a Digital Photo Sensor Tach to check actual and compare it to your installed tach to see what the problem is there. Adjust your idle with the Digital Photo Sensor Tach according to the specifications, and then you can access your speed through the water in gear and your engine is at idle.

Like others have said, sailboats glide through the water with surprisingly very little resistance, thus idle speed will get you a few knots of speed in a calm setting.

Digital Photo Sensor Tach: http://www.harborfreight.com/digital-photo-sensor-tachometer-66632.html
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
Usually I maneuver I close quarters by shifting in and out of gear. Short blasts of power and then just gliding.
 
Sep 6, 2011
435
Usually I maneuver I close quarters by shifting in and out of gear. Short blasts of power and then just gliding.
I do a lot of that too. One issue semi related is my shifter is mushy (no obvious neutral position) so I have to watch prop wash. I haven't gotten to that on my list yet so my gear changes are fuzzy which doesn't help. I need to look into the pedestal or saildrive and see if it had stops/clicks for neutral. Nothing like approaching a busy channel thinking you are in neutral and seeing you're still in gear doing 3 kts and accelerating with the current and a small boat appears from behind the seawall with right away.

Maybe the shift position indicator is an easier item to solve. The two together though make things a bit complicated. If I solve one the other is manageable.

I've always thought my idle speed was above average which is why I asked. I'm not dealing with tides or strong currents which is probably a big factor.
SC
 
Jan 25, 2011
2,437
S2 11.0A Anacortes, WA
SC, youre probably not going to solve the "mushy" shifting. One of the selling features of a saildrive, back then, was smooth shifting without all the clunking. However it is positive enough that you can rely on handle position. My shift handle is on the rear of pedestal going up and down. If it is level, its in neutral. There is a little feeling in it when the gears are released in the SD. The cable needs to be in good shape..