R25 OB speed

T

trailertrawlerkismet

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Feb 23, 2011
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Fluid Motion Model
C-24 C
Vessel Name
(2022) Kismet
I have a question for R25 OB owners that have the 250 Yamaha. I’m looking to find out the top speed, best cruising speed and the associated mpg/gph numbers. Thanks.

Jim F
 
Have you found the performance reports Yamaha has posted? https://yamahaoutboards.com/en-us/home/ ... hp/v6-4-2l They have not tested a 250 hp on a Ranger Tug but they did the 200 hp for the R23.

https://yamahaoutboards.com/en-us/home/ ... -11-14_owa

I have found their report to be fairly accurate of my experience. My rpm sweet spot is closer to 4200 and top speed on flat water about 30 mph. Getting up on plane helps performance. I’m sure that the R25 OB would experience similar performance.
 
trailertrawlerkismet":3j27btf1 said:
I have a question for R25 OB owners that have the 250 Yamaha. I’m looking to find out the top speed, best cruising speed and the associated mpg/gph numbers. Thanks.

Jim F
Click to expand...

I'd wait for the Yamaha official performance report for the RT R25/OB. Likely will be out sometime over next year. It took Yamaha about a year to issue the R27/OB performance data, and it was very close to what I observed for my R27/OB.

I would expect the WOT speed for the R25 to be up at around 40 mph.

You could use the current Yamaha R23 and R27 performance charts and interpolate to get an approximation for the R25.
 
The Yamaha F250 and F300 both use the same service manual. They're that similar. The R27 and R25 are close in size and weight as well. Also note, we pay little attention to weight. We bring what we want on the boat and go. (We don't spend any effort trying to lighten the load to get better fuel efficiency). The F200 on the R23 is a different service manual, different engine.

The F250 and F300 are recommended to run with 89 octane per Yamaha. The Yamaha has knock sensors so running 87 octane won't hurt, but results in less horsepower. On Puget Sound I can get 89 octane at Des Moines and Oak Harbor. Everywhere else that I've found has been 87 octane. Channel Surfing gets the 'good stuff' on occasion, but generally is running on 87 octane (ethanol free gas only). 87 Octane with 10% Ethanol is 85octane fuel, and the ethanol increases the octane to 87. I'll always take ethanol free every chance I get.

For a 2021 R27-OB with the Yamaha F300

For planning purposes using Navionics, I use the following data:
Slowboat: 6.8kts at 2.5gph.
Cruise: 25 kts at 16gph.

More details...
We can slow boat at 6.8kts, 2.8nmpg, 2.5gph at 1700rpm. The slower we slow boat, the better the fuel economy would go (seen as high as 4nmpg)

If we slow boat on the 9.9kicker, we get approx
1gph at 4.8kts at 7/8th throttle.

On the main engine, at cruising, 4500rpm, 25.5kts, 15.6gph and 1.6nmpg.
The best fuel efficiency is between 4200 and 4500 RPM, depending on sea conditions.
Engine trim is 2 or 3 dashes only.

WOT is 35kts. 5600 rpm, 27gph, 1.3nmpg. Get there super fast and spend more time enjoying the destination.

At 10kts I see 1.9nmpg, which is close to what I can obtain doing 25 kts.

Faster than 10kts and slower then 22 kts, is pretty much how to burn fuel fast and get not much for it. (Inefficient).
(Faster than hull speed but slower than planing speed)

On plane, depending on conditions of wind and current, I see 4200-4700 rpm, between 22 and 28 kts.

At 150 hours on the engine, traveled 1,526nm, 968 gallons of gas consumed, we averaged 1.57nmpg (1.8mpg) over this summer.

Hope this helps.
 
Couple observations from having an R23 for a couple years:

I get about the same speed and planing status as in Submariner's post, but about 15-18% better mileage. (much lighter boat) So guessing the r25 is in the middle somewhere. There is a sweet spot for every condition, trim and weight--the 23 at least is very sensitive to trim and waves. Not a big deal when you get used to it.

Now the caveat--the prop. The 23 stock prop is a yamaha 3 blade that is optimized for speed. And it is fast. However, you give away bite to get the speed; I switched to an offshore 4 blade prop. This is better hole shot (to get on plane especially if heavy), better grip in a turn, better speed/turning control in wavy conditions. AND much better mileage/control when not on plane up to about 12 kts because of the stern lift that prop generates. But its about 10-12% slower top speed on flat water. I think the advertised top speeds of these boats on puget sound is a little scary due to decreased reaction time--with all the logs and such so I tend to run around 22-23kts max and can hold a plane easily down to 18-19 depending on load and conditions. And (as I found out) even a small branch can affect a prop that hits it at speed if you plane right over the top of it. Oops. So, there you are.

Other things that affect speed over ground in this kind of hull vs the semidisplacement R29/31 are side winds--the R23 hull shape is pretty flat on the part that planes, so in order to maintain course in side wind you end up crabbing a bit (you can see the prop wash divert) and that will cost you some. Similarly when docking can be tricky if you try to turn sharply and the boat had any forward motion at all--kind of slides sideways. Easy to work around that once you get the feel. But that is a different thread.

Anyway, hope that is helpful.
 
Shibumi: Yes, for my R27/OB the slightest beam wind would cause my R27/OB to move sideways quickly, and in a 20 mph beam wind it makes docking VERY difficult if docking on the lee side of the open dock. With this sort of high wind one really does need the help of a dock hand. I recall, having do dock on the lee side of a dock with a 20 mph wind on my port beam and only after 5 attempts and finally a few fellas on the dock was I able to dock by getting my bow in for the dock hands to grab and hold me while I used the OB to power in the stern to the dock side to tie up.
 
Thank you all for your personal knowledge with the OB’s on your RT’s. We’ve had single and dual engine inboards for 25 years or so, with each boat (32’, 42’, 40’, 27’ n 29’) having its own particular learning curve. Going back to an outboard after 25 years will test my handling memories, so it’s good to know what to look for.

Jim F
 
trailertrawlerkismet":3v52p5n9 said:
I have a question for R25 OB owners that have the 250 Yamaha. I’m looking to find out the top speed, best cruising speed and the associated mpg/gph numbers. Thanks.

Jim F
Click to expand...

A tugnut member on the FB forum said in a comment last week that the top speed on his R25-OB was 45mph.
 
We are new with our RT25OB and we have found we can hit a top speed at about 42 mph and we like slow cruising at about 2300 rpms at 10 mph which gets us fuel usage at about 3.3 mpg. If we need or want to get moving faster we run at about 4100 rpms at 28-29 mph at a fuel rate of 2.6 mpg. This is fully loaded fuel, water and food two adults and a dog. Again we are just starting with our 2021 but loving it and enjoying the PNW.
 
Thank you for the updated/current info on MPG vs RPM n Speed. Congratulations on your new R25OB.

Jim F
 
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