Idle Speed Cruising?

[Rurudyne]

Old salt,I've been doing this for years in the interest of range.

Where I am is very fast (6 to 18 knots) tidal currents,ocean currents,and storms can blow up quickly so I can speed up and get to a hidey hole if need be. Trawlers either have to wait hours for the tide to change,or get up at 4am or some rotten hour (on holidays...really?) to avoid them. I merely ease on the throttle for a few minutes (cost of $20?) and go though.

Of course there are many varying vessels and some are pigs while others aren't.

Points:
-When they're bigger and heavier they don't wander about.
-my past boat,a 48' (capable of 33 knots) would get 3.5 mpg at 7 knots.
-my current 68' (capable of 34 knots) still gets over 2 mpg at 8 knots and 7 knots about 2.4.
-don't know behaviour of smaller boats,but both of them once they pop up on plane the MPG varies little all the way up to 28 or so. The 68 pops up on plane at 15+ and it's at .6 mpg, and at 27 knots it's at .5 mpg,but at 34 less than .3. Needless to say I never run it there.

Looking at trawlers in the 40'-45 range-much smaller with vastly less interior space and not the luxury-usually get about 2 to 2.5 mpg or a bit more IIRC at 8 knots...

Edit:

I did a quick look and am shocked/disappointed at the mpg on a 35 Nordhavn coastal boat...half the length of the 68 and worse mpg much of the time
https://books.google.ca/books?id=9Z...KcQ6AEIKDAB#v=onepage&q=nordhavn mpg&f=false

For friends and family member who want to go fast I've joked about a coin OP throttle. Naturally that wouldn't be practical ... though with one of these cheap to use credit card machines....

 

[missinginaction]

Well oldsalt, practical is a judgement call but I'm doing exactly what you're describing.

I restored a 1973 Silverton sedan (27'). This is a v-drive boat and with the original 302 Ford V-8 is underpowered. Rather than jump through a lot of hoops, I just run her at displacement speeds which are right around 6-7 MPH.
Like you I'm in no big hurry.

I'm not idling though. I typically run around 1500 RPM and can push her up to 2000 before the wake starts getting to large. A big reason I run a little faster than idle is engine issues. I think that idling for long periods can lead to fouled plugs and an engine that gets gummed up with deposits from incomplete combustion. At 1500 RPM or so I'm still running slow but I'm putting a bit of a load on the engine, which helps it run better for longer I believe. I run the boat in upstate New York, primarily on the Erie Canal / Hudson River.

Whitepointer makes a couple of good observations. I've owned stern drives in the past and as he says they are a challenge to run at displacement speeds. They're just not designed to do that.
He also makes a comment about high thrust outboards.
I picked up a Yamaha T9.9 over the winter and am just now finishing up work on my boats transom and swim platform. The little Yamaha will be mounted back there. My plan is to lock the outboard in a forward position and steer with my rudder.
The boat should be launched by the end of the month. I'll reply to this thread once I have some experience with this set up.

Regards,

MIA

 

[WestVanHan]

For friends and family member who want to go fast I've joked about a coin OP throttle. Naturally that wouldn't be practical ... though with one of these cheap to use credit card machines....

When they hear it's about $10 a minute in fuel at WOT it gets quiet.
$20 an hour toodling along is much better.

 

[FAST FRED]

"For friends and family member who want to go fast I've joked about a coin OP throttle."

Coin operation is hard to do as some folks will create a mold and freeze water in the size of the required coin.

 

[Rurudyne]

"For friends and family member who want to go fast I've joked about a coin OP throttle."

Coin operation is hard to do as some folks will create a mold and freeze water in the size of the required coin.

Random thought: do what casinos do and make them buy tokens ... also good for your one armed bandits or other games in the saloon.