BF250 How many RPMs is yours turning at WOT?

I haven been testing a couple of different props on my BF250. I would like to know what RPMs others are turning at WOT on their BF250?

The manual lists the BF250 WOT operating range as 5300-6300 rpm. This is the first large 4 stroke I have ever had. In the past with 2 strokes I have always propped to so that WOT RPMs are very close to the maximum allowed. I have seen online that peak horsepower is achieved at 5800 rpm. During my prop testing I have found this to be true. During testing most of the props pull strongly up to 5800 rpm. After this point the increase in rpm is much slower. I have tested props that have peaked at 5900 and up to 6200 RPMs. I am just wondering if there is any benefit to trying an prop closer to 6300 rpm or whether being able to 5800-5900 rpm would be better. I got better cruising economy with the prop that only achieved 5900 rpm WOT. Which makes since as it is a larger diameter prop. I just want to make sure I am not overpropping the motor. Overpropping could could can cause unnecessary stress on motor I have also heard overpropping can lead to 4 strokes making oil.

Just starting the same process, I recently repowered my Intrpid 377, went from trip 225s to 250s. We started off with my old honda 4 blade 14 1/4x 17 and they turned max rpm with 300 gallons of fuel, pretty sure I was hitting the rev limiter.
just swapped on some Mirage plus 3 blade 15 1/4 x 19, waiting for the weather to calm down so I can test them.
FYI, top end was only 3 mph better, and at 4300 cruise was actually down by almost 3mph.

Did the rev limiter kick in at 6300 RPMs or did you see higher? My BF250 is a single mounted on custom aluminum bay boat. I have tried a few props. I have a Honda 14 3/4 x 19P 3 blade (I think it is a rebranded Solas Titan). I can turn it to 6200 rpm and a little over 50 mph, but it ventilates during turns. I have a Solas Rubex L3 that is 16" x 19P (I think this is the same as the large diameter Suzuki props). Can only turn it to 5900 RPMs speed is a little over 50 mph. Cruise economy is much better with this prop. I can cruise at 30 mph at 4.5 mpg. I am just not sure 5900 RPMs WOT is high enough.

Currently I have a Mercury Rev 4 19p I am testing. RPMs at WOT is 6100 and 49.5 mph. This rev 4 prop never loses grip, boat can be turned hard over at any trim angle an prop never loses grip. Hole shot is good. Cruise economy is lower than the 16" diameter 3 blade though.

I have just found during the testing of the props that after 5800 RPMs the motor does not pull as strong. But In the past I have always propped boats to run very close to or slightly over the maximum allowable rpm. The previous 2 strokes I had would only have a 500 rpm operating range compared to the 1000 rpm operation range of the BF250.

I just would like to get some feedback from people if they are propping to allow the boat to turn all the way to 6300 rpm or are people are happy if they can turn say 5800 rpm which is midway in the operating range.

the factory says 5300-6300 is ok,you shouldn't ever be running her at 6300 rpms for any length of time,your wot will vary a bit with different loads and other conditions,# of passengers,load of gear and fuel,beer,ice coolers,etc. water and weather conditions

My 225 hits WOT at 5900 rpm on an old heavy (6000 lb. loaded) CHawk 25 using a 14.25 X 15 prop with no issues and I'm just under 2000 hours operating time. So my personal opinion is that that prop that is giving you 5900 rpm would be fine. As Johnny pointed out, that WOT will vary considerably based on the weight you are carrying at any one time. With 120 gallons of fuel and four adults on board, the old girl won't go over 5600 rpm.

Chawk_man thanks for the info. The max operating range on the BF225 is 6000 rpms so lightly loaded at 5900 you are close to that. Heavily loaded you are still in the upper halve of the operating range. In my opinion there is nothing more detremental to the longevity of an outboard motor than overloading it. Overloading an outboard motor can be compared to pulling a 15,000 lb load with a 1/2 ton truck. It will do it, but not for long. As you stated the max rpm will change based on a load, and at some point I will probably wind up with 4-5 especially fat guys or gals with the food and drinks they require on the boat. This is why I feel is best to prop towards the upper RPM range when boat is loaded normally, just as yours is.

Johnny, I don't run around at WOT all the time, burns too much fuel. But some bass boat guys have 2 speeds stopped or full throttle. I do make is a point to operate the engine at WOT at least for a couple of minutes nearly every time I use the boat. Ensuring that the motor can operate at or near the WOT RPMs it "normally" does ensures that there are no issues with the motor. An outboard motor can operate surprising well at normal cruise speeds on 5 or 5 1/2 cylinders.

Well said immoody, Good luck and happy boating!!

Roger that on running at WOT.
On my BF 225 on the CHawk, at 5900 rpm WOT, yielding 39 mph, the burn rate is 20.1 gph.
At 5000 rpm, yielding 33 mph, it's 15.0 gph.
The cruising sweet spot is 4600 rpm, 29 mph, burning 9 gph.
In other words, going from 29 mph to 39 mph costs and additional 11 gallons of fuel per hour.

I charted all of that several years ago when I had a beautiful flat water day and the fish were taking a long nap.

Well noted chawk​man, good reference material for people in the know, It pays to document.

I did some more testing with the mercury rev 4 19 pitch prop. My boat is a custom aluminum bay boat. motor is mounted on bracket and total LOA is 24". Estimated the weight of the boat during this test was 4700-4800 lbs. Fuel full, live well full, 2 people on board loaded for fishing.

0-30 mph is 6.3 seconds. Minimum planing speed is about 18 mph.

The BF 250 is capable of some very good MPG figures if engine rpms are kept below 4500. Around 4500 rpms the VTEC system kicks in and fuel economy starts to decrease. And if fuel economy is a major priority keep the motor in between 3500-3700 RPMs.

The 4 blade rev 4 is slower by 2-3 mph top speed than a couple of other props I have tested.But top speed is not a priority for me. The Solas Rubex L3 16" x 19P prop will return better fuel economy but is slower to plane. Also when planing of the bow rises and stern "sinks" in more. I fish in the Louisiana marsh so planing time is an important factor.

IMO those numbers for the Mercury rev 4 19 pitch prop are outstanding. Question - how are you measuring slip?

BTW - I didn't think the VTEC kicking in increased fuel consumption. In fact, I've always thought that it made the engine more efficient at the high end. At least that's what is implied in the technical description of the Honda VTEC system in Chapter 18 of the Helm Shop manual for my BF 225.

I used the mercury prop slip calculator http://www.mercuryracing.com/prop-slip-calculator/ The calculator may not be 100% accurate, but is does give idea on slip. During testing the slip calculator agrees with seat of the pants feeling operating the boat. I also believe that some props are actually higher pitch than the manufacturer states which affects the slip numbers. I don't believe prop slip in itself is the way to choose a prop. It is just a factor that can be looked at.

You are probably correct about the V-tec not causing the increase in fuel consumption. The fuel economy is probably diminishing due to the engine work load increasing as the rpms/speed increase. Without the V-tec the fuel consumption rate could possibly be even higher.