Cruising speed of a R25 with 150cummins or 180yanmar

[Kpeters]

Can those of you with an R25 classic chime in about your cruising speeds and WOT speeds? I'm looking at a 25 with 150cummins and another with the 180yanmar. I'd like to be able to cruise around 15knots. I don't know if this is realistic on a 25. Thanks for your help
Kate

 

[South lake]

WOT on my 2010 is just under 20 mph or just over 17 knots. I typically cruise at 10 or 11 knots. Slower than that if I'm running the generator for A/C. My engine is a Yanmar 150. Not aware of any R25s with 180s.

 

[Levitation]

15 knots as a sustained cruise speed is uncomfortable in my R25 due to bow rise (in spite of trim tabs) Steering becomes loosey goosey.While I run that speed for specific reasons and for a limited time, soon as possible I am back below 10.
OTOH I like 6 knots- 1 gph dontchaknow :mrgreen:

 

[NorthernFocus]

We have the Cummins 150 and not enough sea time yet to have learned to trim the boat for optimum performance. But so far at 3300 RPM (75 percent throttle per the computer) we make about 12 knots. We're only getting 3850 RPM at WOT which gives us between 15-16 knots. Top end is supposed to be 4000 RPM but for whatever reason we can't get there.

Keep in mind that these engines are designed for recreational use and have an 80 percent continuous duty rating. That means they can operate indefinitely at 80 percent load but WOT is basically intended to be emergency power.

 

[hughesdave123]

We have the Cummins 150 and not enough sea time yet to have learned to trim the boat for optimum performance. But so far at 3300 RPM (75 percent throttle per the computer) we make about 12 knots. We're only getting 3850 RPM at WOT which gives us between 15-16 knots. Top end is supposed to be 4000 RPM but for whatever reason we can't get there.

Keep in mind that these engines are designed for recreational use and have an 80 percent continuous duty rating. That means they can operate indefinitely at 80 percent load but WOT is basically intended to be emergency power.

I have the same issue with my 2008 25 classic with 150 Cummins . I was told by my surveyor to get the prop adjusted down 2 degrees to get the full 4k from the advertised engine manufacture documentation . I'm waiting to get my trailer so I can go get this done.

As for speed I get 12 knots at 3300 rpm 15-16 full throttle 3850 rpm. Ill repost when I get a chance to
1: clean and repaint bottom.
2: adjust the prop .

 

[knotflying]

My experience has been that there are other factors that can affect RPM, not just prop pitch. If my boat is loaded with fuel, supplies and clothing I can loose as much as 150 RPM. Then if I get any growth on the bottom it can go down a bit more. Water type and temperature also has its affects as well. So before I went and started changing prop pitch I would observe the other factors.

 

[NorthernFocus]

...I have the same issue with my 2008 25 classic with 150 Cummins . I was told by my surveyor to get the prop adjusted down 2 degrees to get the full 4k from the advertised engine manufacture documentation ....

FYI, I'm already running the lower pitched blade(i.e.17x14) of the two specified by Ranger. Also thus far have been operating fairly lightly loaded. That would be two adults on board, half a tank of fuel, full water tank, factory supplied ground tackle, no holding tank, and very little in the way of spare part, tools, provisions, etc. In spite of all of the above, WOT is 3850.

 

[PhilR]

My R-27 with the Yanmar 180 has a top speed of 19-20 knots at 4,000 rpms....two persons aboard, normal gear, half tank of fuel. This is in fresh water with a waxed hull (yes, I wax the bottom, no paint).

Phil

 

[NorthernFocus]

My R-27 with the Yanmar 180 has a top speed of 19-20 knots at 4,000 rpms....two persons aboard, normal gear, half tank of fuel. This is in fresh water with a waxed hull (yes, I wax the bottom, no paint).

Phil

I was going to suggest to the OP, if you want to cruise at higher speed, get a longer boat. Like a 27 😀

 

[Rodeo]

I have been wondering about what to expect under normal conditions from the Cummins. Since we keep the boat on Lake Yellowstone at an elevation of 7,800 feet our horsepower is so degraded that we only operate at slightly higher speeds than my old sailboat (not that there is anything wrong with that).

 

[NorthernFocus]

I have been wondering about what to expect under normal conditions from the Cummins. Since we keep the boat on Lake Yellowstone at an elevation of 7,800 feet our horsepower is so degraded that we only operate at slightly higher speeds than my old sailboat (not that there is anything wrong with that).

At least on the lake you don't have as far to go as many do :mrgreen:

 

[Tug@myHeart]

We are at Tahoe with the Cummins 150 with a sea level prop the boat would not get out of its own way. But with a new prop set for 6200 ft....no more black unburned fuel and the RPM are up at 3950 with a 1/2 loaded boat. Speed is relative....we are not in a hurry to get to the other side of the lake. Just want the engine to run at the correct RPM. All that said we can get up to 16mph at 4000rpm. Cruz at 13 at around 3300 More HP is not always the answer. But as they say there is no replacement for displacement.

 

[Dave Patstone]

I have a 2013 R25SC with a Yanmar 150 (don't know of any with 180's).
My tug, full fuel, full water, full provisions, 2 people, no waste and in fresh water @ 1100 ft. above sea level.
WOT 3630 to 3650 rpm giving 16.3 mph using 8.0 usgph.
I travel a lot at 3530 rpm. giving 15 mph using 7.2 usgph, I will back out of it about once an hour and run at 2000 rpm for 5 min then right back into it.
Best economy (except for dead slow) is at 2000 rpm giving 7 mph using 2.1 usgph.
Going from 7 mph to 8 mph exactly doubles fuel consumption and the boat starts to dig a hole leaving a large wake.
Because I run this hard I am very fussy about oil. I run Shell T6 full synthetic and do 50 hr. oil changes and I run Mann oil filters.

 

[NorthernFocus]

...with a new prop set for 6200 ft....no more black unburned fuel and the RPM are up at 3950 with a 1/2 loaded boat...

What are the dimensions on the "6300 ft prop"?

 

[nzfisher]

Every vehicle with a diesel has a "sweet spot" where the harmonics of all the drive components and systems are happy. I am talking about sound, vibration, speed and fuel consumption- basically feel. On my boat, an R25sc, it is 3300-3400 rpms. Conditions outside the system dictate the speed- wind, current, chop and swell. Yesterday is was a flat ocean with little wind so the speed was 14 with the tide about 11 against.

 

[tugnnaweigh]

My 2008 R25 with the QSD 150 needed adjustments to the propeller to make the correct RPM at WOT; it would do it in neutral so there was no problem with the engine, it just couldn't get there under load.

The boat was heavy as I dive and fish so after having the prop de pitched two pitches, (that's the maximum according to my propeller guy) and having it de cupped from .105 to .060 I found it still wouldn't make correct RPM at WOT and began taking weight off. Sure enough, that was the solution and there was a surprising amount of weight to take off!

As much of the weight was going back on I ended up having 1.5 inches taken off the diameter to achieve correct RPM at WOT in my application.

Keep in mind a lot of boats this length have two or three times the horsepower so we're not exactly over gunned right out of the gate!

Diesels are often operated by RPM more than MPH or KTS which is my preference. I heartily agree with the poster above that feels this powerplant really "settles" when operated in the low 3000 range which also is that 80% duty cycle others refer to.

 

[hughesdave123]

...I have the same issue with my 2008 25 classic with 150 Cummins . I was told by my surveyor to get the prop adjusted down 2 degrees to get the full 4k from the advertised engine manufacture documentation ....

FYI, I'm already running the lower pitched blade(i.e.17x14) of the two specified by Ranger. Also thus far have been operating fairly lightly loaded. That would be two adults on board, half a tank of fuel, full water tank, factory supplied ground tackle, no holding tank, and very little in the way of spare part, tools, provisions, etc. In spite of all of the above, WOT is 3850.

I just wanted to post an update :

So I DID make the pitch change in my prop last year when it was up on land over the winter.
This Memorial Day weekend I got to put her in . Funny thing is I forgot I had the prop adjusted when I took it out this weekend. I was trying to figure out why I was hitting 18-19 knots with a full tank fuel , full water, half poo tank and 3 kids and a wife on board . Then it hit me . THE PROP ADJUSTEMET WORKED ! WOOO HOOO!

OLD= 2600 RPM = 8-9 knots 5 gph
NEW= 2600 RPM = 12 knots 3.2 gph

MAX -
Old = 3600 RPM =14 knots 8.6 gph ( this was at full throttle on old setting and tug struggled and boat EMPTY )
NEW = 4k RPM = 18-19 Knots 7.6 GPH ( paced with everything and wife and kids)

The best part , it feels like it gets up on a plane better now , and the bow dosnt pop way out of the water anymore .

 

[NorthernFocus]

...So I DID make the pitch change in my prop last year when it was up on land over the winter.
...

What pitch are you running now?

 

[hughesdave123]

...So I DID make the pitch change in my prop last year when it was up on land over the winter.
...

What pitch are you running now?

I don't know , Ill ask the yard that did it . it was stock since 2008 , when I bought it last year my surveyer told me it shoud be de pitched down 2 clicks , I took the survey to the yard and they did it.

Is no fluke , I could replete the speed again this weekend , also at 4k rpms full load , she only runs around 185-187 temp.