Minimum boat speed under power

[Sonrisa]

Hello!

I am curious about what minimum speed peoples boats will go under power. On a 32 foot waterline, our minimum "marina speed" when in gear is still 2.7 knots, which is faster than I would like.

What is your minimum speed in gear?

Thanks!

[rslifkin]

Ours is a powerboat and powered to plane, so it moves fairly quickly in gear. Both engines in gear at idle takes a moment to accelerate to full speed, but it'll settle around 4.2 - 4.3 kts just idling. One engine in gear is closer to 3 kts. So coming into a marina, once we're in close enough we're usually coasting in neutral with just quick bumps into gear for maneuvering.



33.5 foot waterline for us.

[Rucksta]

1.2 knots 37.5' WLL fin keel with long root narrow tip hi aspect spade rudder turns easy forward or reverse, doesn't stall.

Single control lever adjusted to select gear before opening fuel lever.
Engine speed drops about 100 RPM from idle of 850 RPM on selection of gear.

Makes changing gear very easy and minimises initial prop walk and dead helm when changing direction..

[TrentePieds]

Sonrisa said: "I am curious about what minimum speed peoples boats will go under power. On a 32 foot waterline, our minimum "marina speed" when in gear is still 2.7 knots, which is faster than I would like.

What is your minimum speed in gear?"


If you are frightening yourself by coming into your marina at nearly three knots, your basic problem is that you keep the boat "in gear".

The minimum speed of ANY sailboat while the engine is running is ZERO knots TTW ("Through The Water"). However, the speed OTG ("Over The Ground") is what matters in close quarters, and part of learning boat-handling is to learn to maintain ZERO speed OTG in any prevailing condition of wind and current.

A 13-ton boat is a big hammer, so you are right to be anxious about handling her in tight quarters, but it is not difficult to do. A prerequisite is that you eschew ALL "knowledge" you carry with you from handling a car ashore. That should not be too difficult to do since the native configuration of the "Ingrid", as of all other Colin Archer derived boats, is tiller steering. If yours has been retrofitted with wheel steering it would no doubt be a little more difficult to leave your shoreside habits ashore where they belong, but it is quite doable ;-)

Not only should you be able to hold position OTG in every combination of set and drift, but you should also be able to "pirouette" your ship through a full 360º change of heading while doing do. Again, not difficult to do, but what "knowledge" you bring with you from handling a motorcar will impede your learning.

You say you are in Saltspring. I am in Ladysmith. If you care to send me a Private Message we can see if we can meet up this spring and I will teach you how it is done and how to bring her in and out of her slip without scratching anything and without the danger of filling your knickers :-)

All the best,

TrentePieds

[Sonrisa]

Thanks TrentePieds. Not having docking issues, just curious about what minimum speed others are seeing, while in gear.

[Shrew]

Originally Posted by Sonrisa

Thanks TrentePieds. Not having docking issues, just curious about what minimum speed others are seeing, while in gear.

I run somewhere around 2.5 -2.7 kts at idle in gear. I bump it up to 1,000 rpm which has me around 4+ kts if travelling through no wake zones.

If you need to go slower than your idle speed, periodically bump it into neutral, then back into gear. Repeat periodically to maintain your desired speed. I usually only do that in close quarters (mooring fields and tight anchorages) and when docking.

Slower than 2 kts and I start to loose steerage. At that speed and slower, it requires exaggerated rudder input for small changes in course.

[TrentePieds]

Sonrisa:

3 knots would be perfectly normal. The thrust required to bring an Ingrid/Astrid/ Redningsskoite to 3 knots is very little indeed.

TP is 5 tons with 25Ft LWL, but fin-keeled . She has a 20HP Beta with a 16 x 14 RH prop (as recall just offhand). Idling at 850RPM in forward gear she does 3 knots on flat water, I'm sure, but as you may deduce from what I said in my previous, it's not anything I pay any particular attention to since it's trivial in terms of maneuvering.

TP

[Rumrace]

I had a Sea Ray 330 with Modified 504’s
The factory speedo could record the speed. The GPS showed both engines in gear 3kts
Idle 800rpm. At 4300 RPM 51.4 kts.
To travel at channel speed 10 kilometres per hour I needed 1200 RPM. No wake I was comfortable with 1000 rpm.
The sailboat is not as maneuverable and prop walk exists in single screw power boats also . I think a little worse. I do miss my twins docking.
You could try looking up your idle speed and assure it’s set correctly but you sound average speed to me.

[sail sfbay]

3 knots.

[boat driver]

Every vessel is different. some need speed to steer, which may or may not be minimum engine speed. Others need engine rpm/speed to operate. Particularly direct drive.
sport fishing boats may be 7 plus knots in idle- and some vessels with large rudders may get away with 1 knot.
The Ever Forward minimum speed is 4.5 knots when not aground.

[dolami]

In my 39 ft fin keel sailboat 2 knts, steerage lost under 2knts, so while in marina I shift from neutral to drive approaching berth.

[Rumrace]

So true. We had an Ocean in our club with big turbo diesels. It was twice my speed in the slips. Like a previous person pointed out power boats do a lot of shifting and have the tough clutches to handle the shifts.
I’ve noted some sailboats are over propped by the owner to get an extra 1/2 knot top speed at the cost of a weak clutch system.
My Dad had a boat in the 30’s and revived it in the 50’s. He never had a motor despite its size I think 25’. There was a spot for a motor but not sign one had ever been installed. We did controlled crash docking.

[goboatingnow]

My old TSDY would do 4.9 knots in tickover with both engines engaged

[michaelratinter]

Idling @ 1000 rpm my speed is 3 kts. 36 foot lwl.

I shift in and out of gear among the slips.

[Niall leslie]

The trick for sailing vessels to achieve ultra low boat speed in gear is to have auxiliary electric drive such as that provided by Beta. It is close to perfect for confined areas.