Light boat with Bravo III

[rock doc]

Here are the specs I have:
2000 Maxum 2300 SC weighs approx 4500 Ibs
23' deadrise
Bravo III with 26p stock prop set
7.4l mpi

The drive has be repainted and I can;t read the serial number. It is also not on the top of the motor. Right now I am hitting the rev limiter at 48 mph (gps) with 4 people on board and full tank of fuel. My tach seems to be reading a little high. The info I have read on this forum indicates the rev limiter kicks in at 4680rpm (my tach is close to 5000 rpm). Using the prop calculator it looks like it has a 2.2 gear set - yielding a slip of 8-9%.

Any thoughts on what to do? I don't know if someone swapped the drive on this boat at some point, but it seems to be very under propped.

 

[rock doc]

No Title

Here are a few calcs using theoretical pitch numbers.

 

[rock doc]

Assuming a gear ration of 2.0 the slip number jumps to 17% with a 26P prop, which seems high based on what I have read.

 

[alldodge]

Don't see a 2.2 being on your boat unless someone replaced it, which it probably was. My 23 footer came with a 1.5 drive. The motor max rpm is 4800 and the limiter should be 4900 or so. Being you tach is reaching 5K, I would say your in the ball park. Right now with the boat only reaching 48 mph I would say you might just be trimming up to much and your slip is higher, and your drive may be a higher ratio.

My 23 has a 7.4 B1 and reaches 60 mph with a 21 pitch and weights 4800 dry. Find out where the cav plate is straight and level with the bottom of the keel. Run cruise and WOT without changing the trim, keep it flat. At this position calculate your slip

 

[rock doc]

Pretty sure the rev limiter is 4680-4700 rpm on an MCM MPI. This is not my 1st boat - it is trimmed out properly. I would not ventilate a prop to the point that it would lose grip and bounce the rev limiter. I agree the gear ratio seems oddly low - more in line with a heavier cruiser. Wondering if someone changed out the lower drive at some point.

It could be a 2.0 ratio, but that would give approx 15-17% slip, which seems a little high for a BIII. Having said, I found the following test information online:

"Single 300-hp MerCruiser 350 MAG MPI Bravo One V-8 gasoline stern drive with 350 cid, 4.00" bore x 3.48" stroke, swinging a 24"-pitch propset through a 1.5:1 reduction."
Reported top speed was 50mph which would place the slip ion the rang of 28-34%.

Based on my research I don't think our Maxum 2300 SC will go faster than 55mph on GPS but there is very limited info on this boat and power package online. I'd really like to try 30P but the props are too expensive to experiment. Any guidance would be appreciated.

 

[alldodge]

Agree with your rpm

Single 300-hp MerCruiser 350 MAG MPI Bravo One V-8 gasoline stern drive with 350 cid, 4.00" bore x 3.48" stroke, swinging a 24"-pitch propset through a 1.5:1 reduction

Have not seen/read this one

don't think our Maxum 2300 SC will go faster than 55mph on GPS

Then your in the sweet spot not, with 4 people aboard.

Personally I think you need a 1.5 drive so you can turn a prop with less pitch, so it will turn faster and not try to grab as much water at one time.
My current two years testing with a 11K pound single engine cruiser B3, ratio 2.0 drive
22 P 4 blade, cruise 3800 rpm speed 34 mph (14%), 5250 rpm speed 47 mph (14%)
26 P 3 blade, cruise 3800 rpm speed 36 mph (26%), WOT 5200 rpm speed 50 mph (22%)

This is a heavy boat, so having more slip is actually a benefit, only draw back is slower hole shot. I'm still working with a vendor and have some other things to try. My 23 footer as before B1, 21 P 3 blade speed 60 at 4800 rpm (6%). Will say its been a while since I ran the boat at WOT but so long as it stays together there should be no issue

 

[rock doc]

6% slip is pretty darn good. Thanks for the pointers. I have read a fair bit and it all seems very boat specific. It seems like the Maxum hull is slow when compared to some similar boats such as a Rinker or Regal. Having said that, I just want to get our boat ironed out so the motor is withing its operating window. We won't be running above 35mph very often.

 

[Scott Danforth]

Many larger marinas have props to try

 

[rock doc]

There are not any marinas around here that stock BIII props. I was hoping to buy used off ebay or kijiji
.

 

[Faztbullet]

That about right for the Maxum ..45-50 mph tops.

 

[QBhoy]

Hi
I'm not totally certain, but was that engine even an option on that boat.
I've seen loads of these 2300sc boats over here (there are 4 within a 100 yard radius of me. One has a 5.0 carb and alpha, the other 3 have a 5.7 and alpha.
May be wrong, but you might have a thrown together combo ? Just a thought.

 

[rock doc]

Hi
I'm not totally certain, but was that engine even an option on that boat.
I've seen loads of these 2300sc boats over here (there are 4 within a 100 yard radius of me. One has a 5.0 carb and alpha, the other 3 have a 5.7 and alpha.
May be wrong, but you might have a thrown together combo ? Just a thought.

It was an option. The motor is stock. Not so sure about the gearing though.

 

[QBhoy]

Fair play Rock. US and UK familiar boats tend to differ...because of fuel prices here, I suppose. Boo !

 

[rock doc]

Fair play Rock. US and UK familiar boats tend to differ...because of fuel prices here, I suppose. Boo !

It is not a common package but they do exist here in Canada. Fuel prices are not far behind UK here. ($1.07/l cdn today for regular = $3.22/gal USD). Our gov reaps some significant taxes of fuel here in Canada.

 

[Maclin]

A B3 V8 final ratio is at the 2.0 plateau I believe. With a V6, rarer combo, the final ratio of 2.2 is used. On larger boats with single engine a 2.2 might show up. I would try to determine the actual final ratio and get some known and reliable perf numbers.

In my opinion, if it is indeed the 2.2 then you really need to go up in pitch (or look into replacing drive with more correct 2.0). If it is the 2.0 then need to look at condition of the props.

Or I may owe you an apology later...either way no charge.

 

[rock doc]

Not a mark on the props. Agree that the ratio seems unlikely to be a 2.2. Too bad the serial number is missing.

 

[QBhoy]

It is not a common package but they do exist here in Canada. Fuel prices are not far behind UK here. ($1.07/l cdn today for regular = $3.22/gal USD). Our gov reaps some significant taxes of fuel here in Canada.

Haha. Still a fair bit cheaper.
Over here, fuel prices are at a real low just now at ?1.14p per litre. Last year they were around ?1.48p. I was in Canada (bramalea) a few years ago and envied the relatives running dodge Rams and other V8's as standard. We are stuck with an equivalent 2.0l 4 cylinder diesel !
One of my friends who wasn't too well off here, recently moved over near Winnipeg full time doing an equivalent mechanics job and now runs a hemi pick up and a Range Rover sport supercharger ! Wouldn't have been an option for him over here.
I left Canada with one main thought in my head.....
The relatives were telling me that it's a shame I wouldn't still be there 3 weeks from Tuesday....as they were planning a big party and BBQ at the house......3 weeks on Tuesday !!!!. The thought of planning a BBQ 3 days away in Scotland is a gamble ! Would love to get predictable weather like you guys do. It's just rubbish over here for that. Probably isn't anywhere nicer than the west coast of Scotland when the sun shines.....but that's not a familiar occurrence.....I suppose it wouldn't look the way it does if it was warm and sunny all the time though....compromise, I guess.

 

[rock doc]

Canada is a great place to live. I live on one of the best waterways on the east coast and hardly anyone even knows it exists. We boat and fish all summer on a vast river system in our backyard.

 

[QBhoy]

Sounds lovely ! If I was to criticise one single thing...there aren't enough pubs local to most !
Maybe that's not a bad thing...

 

[rock doc]

No Title

Sounds lovely ! If I was to criticise one single thing...there aren't enough pubs local to most !
Maybe that's not a bad thing...

I live in a small city of approx 100,000 people. We live on an 1 acre lot with waterfront access and are withing bicycling distance of our city core. I can boat, atv, play hockey, fish, and snowmobile from my doorstep. There are at least a dozen pubs nearby with 3 accessible by boat. We have water on 3 sides. We used to travel fairly extensively up until a couple years ago but lately we have decided to stay closer to home.