Idle speed

Don Lucas · May 7, 2015

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".

centerline · May 7, 2015

sailcruiser said:
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..

Mark Maulden · May 7, 2015

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 · May 7, 2015

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?

woodster · May 7, 2015

sailcruiser said:
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

Mark Maulden · May 7, 2015

You should come up with a 16 x 9. Mine according to survey is a 16x12. Three blade

Mark Maulden · May 7, 2015

You also should take a laser tach to the flywheel.. My tach reads about 400 high

Ron20324 · May 7, 2015

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 · May 8, 2015

sailcruiser said:
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 · May 9, 2015

Usually I maneuver I close quarters by shifting in and out of gear. Short blasts of power and then just gliding.

Mark Maulden · May 10, 2015

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..