Speed and Cruising RPM's

[FiveToes]

28TE Flush Deck Yanmar 315 (2008)

I finally took the Five Toes up the river for a little bracketing this past weekend.

3,000 13K
3,100 13.5K
3,200 14.8K
3,300 15.7K
3,400 16.5K
3,500 17.3K
3,600 18.0K
3,700 18.8K
3,800 19.6K
3,900 20.8K WOT

This was taken in the Niantic River at almost slack tide. Average going both ways. Seems that I have seen greater speeds posted on the site from engine box owners than the FD owners. I certainly cannot get up to 24 knots reported by some owners. My boat seems to ride with the best attitude around 3,400 - 3,500 rpm. That seems higher than a lot of cruising rpm's for other owners posting on the forum. but just seems like the hull sits deep in the water on the lower end, and has the best handling and position at around 3,400 - 3,500 rpm when cruising to our fishing grounds. my brother is a Fortier owner and thinks I'm running it too hard, but others have quoted Yanmar who says that the engine should be able to run at 3,600 all day with no adverse affects on the engine. Of course, these RPM's have not considered fuel efficiency data which I'm now tracking and collecting. But just talking about boat handling here.

thoughts?

[Tree]

What is your transmission ratio and propeller size and cup?

[jleonard]

How deep was the water? I don't know about the Albins, but my old Mainship needed at least 10 feet of water to be able to run full speed.

[Paddy]

Engine box model for me, but at 3200 I cruise at 18-19K all day, and for the few wide open moments I have hit 23K at 3800'ish. I believe that the normal cruise rpm for the Yanmar 315 is 3000 to 3200, but others can chime in if I am off.

[special k]

3200-3400 is the sweet spot for my 2002 28te engine box w/6lp yanmar. this produces 18-20 knots in fac conditions with a slight bow up attitude. slightly slower in seas and current. wot around 3800 can give 23k burning more fuel and a little hotter. time for a rid-lime treatment for me.

[rcwhite]

On our 2007 FD we would cruise at 3300 running 16 knots which seemed
to be the sweet spot. In a hurry we would turn up to 3600 at around 20
but we are rarely in a hurry. WOT was 24 at 4000 on the tach in the spring.
We would drop down to 22 or less by fall as the slime built up.

Drag seemed to make more of a difference than weight at the top.
We had the alaskan bulkhead and a 100lb rib on davits.

Prop was a 19x18 cupped 4 blade which I still have if someone is looking for one:)

[furball]

I have a 2006 flush deck and my numbers were pretty close to that this week.
We were loaded heavy for a week on the boat.
In the spring, empty except fuel and clean bottom, about 2 knots faster.

[FiveToes]

Not sure on my prop. Will check that out along with gear ratio. Still learning my specs. Water was 20-30 feet. Seems like the engine box reports higher knots per rpm from most posts I've seen on the forum. Just trying to find the sweet spot for this boat without risking my engine. She seems comfortable at 3400.