Maxum 2300SCR 1991 Information and standard propeller size/pitch - Maxum Boat Owners Club

Maxum2300scr · 01-24-2015, 06:40 PM

Hello All,
Thinking about the summer already even though it trying to snow here, Have not posted before because I wanted to get some use from my boat as it had a few problems after I purchased it. But after a remanufactured 5.7 mercruiser and transom housing I managed to finally get to enjoy it last year, including a couple of great nights in Plymouth sound at various anchorages.
I have been searching the net to see if anybody has any information on these boats, mine is a 1991 2300 scr with a 5.7 V8 4bbl mercruiser with I believe 1 :1.87 gearing on the outdrive and a 14 x 19 mercury lasaer II s/steel propeller.
The boat at WOT acheves approximately 38 mph which is great for a reletively big boat, but it does suffer with a very slow holeshot sometimes if into a wind it is actually hard to get on the plane.
Not that I want to go fast all the time I would just like to be able to cruise on the plane at approx 3000-3500 rpm and with the current set up it more like 3750-4000 rpm. I am wondering what propeller this boat should have as standard, as with the current set up it to revs to approx 4000 rpm as soon as I open the throttle fully and I get the impression it is just slipping in the water until the boat gets to a certain speed the the propeller seems to acheive good bite on the water. I have fitted the hole blanks for the propeller PVS system but I am sure it should have more grip at low speeds. Any information would be greatly appreciated.

mmwjr · 01-24-2015, 07:56 PM

Welcome aboard

What is the WOT rpm? 38 mph seems low for what this boat should be able to achieve. Also what out drive do you have, Alpha Gen 2?

Boat may be overproped which will impact low end performance and top end.

Maxum2300scr · 01-24-2015, 11:24 PM

Quote:

Originally Posted by mmwjr

Welcome aboard

What is the WOT rpm? 38 mph seems low for what this boat should be able to achieve. Also what out drive do you have, Alpha Gen 2?

Boat may be overproped which will impact low end performance and top end.

Thanks mmwjr for the advice and your reply, It is fitted with an Alpha 1 Gen 2 and I am sure it was approx 4600 to 4700 @ WOT with me trimming out. ( sorry if I am a being bit vague but I have not taken it out yet this year) just waiting for the longer days as we are still very much in winter here. I am just trying to get ready for the next season.

mmwjr · 01-25-2015, 01:37 AM

You can call me Mike

Your WOT is correct yet your top speed seems low as well as plane speed. Do you have trim tabs? How much gear and passengers are on board?

Is the prop a 3 or 4 blade?

Have you tried trimming the drive to get on plane?

Maxum2300scr · 01-25-2015, 07:56 PM

Quote:

Originally Posted by mmwjr

You can call me Mike

Your WOT is correct yet your top speed seems low as well as plane speed. Do you have trim tabs? How much gear and passengers are on board?

Is the prop a 3 or 4 blade?

Have you tried trimming the drive to get on plane?

Hi Mike

The trim tabs are the hydraulic type ie: not always in use and I usually have the drive trimmed all the way down at start and trim up after I am on the plane.

The boat is usually carrying two adults and two children with about another 75 kgs of kit.

The prop is a 3 blade Mercury Laser II 14 x 19. It feels like it reves too freely at start off and doesn't grip until we get up to about 25 mph. I am sure the prop is not slipping on its bush, I just think it spins in the water without enough drive.

Thanks

Jamie

mmwjr · 01-25-2015, 09:47 PM

Jamie a stainless prop should have better bite than an aluminum as it does not flex as much, however by not flexing it puts more load on the engine. 2 adults and 2 children is that much of a load for a 5.7 try using the trim tabs as these will greatly increase getting the boat on plane as well as balancing the boat side to side.

If still not happy either go to an aluminum prop or drop one pitch in a stainless.

One more thing is there any damage to the cavitation plate on the drive that may allow the prop to suck air?

shrew · 01-26-2015, 02:43 PM

You're going to be overpropped in order to be planning at 3K. Let's look at it from the problem, rather than the solution. Your goal is to run at between 3000-3500. This would be a reduction from the current 3750-4000. Speed is not a variable being considered. What is the goal of the reduction in RPM? You can reduce the RPM to 3k now. This would invariably drop you off of plane. Your goal to remain on plane. This, in itself is a paradox. How can you both not consider speed a variable AND have a goal to remain on plane?

I suspect fuel consumption is the actual motivation here. If so, then you can't look at gallons per hour alone. Also consider distances. Boats use gallons per hour because gallons per distance vary to greatly based on current, tide and wind. However, I'd be curious to compare the average speeds at 3000 vs the average speeds at 3800. Then consider which RPM the MPG is more cost effective, on average.

Maxum2300scr · 01-27-2015, 05:28 AM

Quote:

Originally Posted by mmwjr

Jamie a stainless prop should have better bite than an aluminum as it does not flex as much, however by not flexing it puts more load on the engine. 2 adults and 2 children is that much of a load for a 5.7 try using the trim tabs as these will greatly increase getting the boat on plane as well as balancing the boat side to side.

If still not happy either go to an aluminum prop or drop one pitch in a stainless.

One more thing is there any damage to the cavitation plate on the drive that may allow the prop to suck air?

Hi Mike

There is no damage to the cavitation plate I will try some variables when i get it out on the water this year. I will keep you posted thanks.

Maxum2300scr · 01-27-2015, 05:38 AM

Quote:

Originally Posted by shrew

You're going to be overpropped in order to be planning at 3K. Let's look at it from the problem, rather than the solution. Your goal is to run at between 3000-3500. This would be a reduction from the current 3750-4000. Speed is not a variable being considered. What is the goal of the reduction in RPM? You can reduce the RPM to 3k now. This would invariably drop you off of plane. Your goal to remain on plane. This, in itself is a paradox. How can you both not consider speed a variable AND have a goal to remain on plane?

I suspect fuel consumption is the actual motivation here. If so, then you can't look at gallons per hour alone. Also consider distances. Boats use gallons per hour because gallons per distance vary to greatly based on current, tide and wind. However, I'd be curious to compare the average speeds at 3000 vs the average speeds at 3800. Then consider which RPM the MPG is more cost effective, on average.

Hi Shrew,

Fuel consumption is not the factor, This is my first boat with an I/O unit an I just feel it revs too much on take off to be getting a good bite on the water compared to previous or other boats on the water.

In my original qote the boat reves to approx 4000+ rpm as soon as I open the throttle with out and hestitation from the engine which dosn't sound taxed in any way.When I listen to other similar boats on the water, they seem to have a more linear acceleration to rpm pattern.

shrew · 01-28-2015, 02:36 PM

The Max RPM range on that engine is 4400-4800 RPM. At Wide-Open Throttle (WOT), when properly trimmed and minimal tab, what is your actual WOT?

Maxum2300scr · 01-28-2015, 05:02 PM

Hi Shrew,

As mentioned in my previous post it is around 4600 to 4700 RPM @ WOT trimmed out with no tab @ approx 38 mph as previously mentioned I have not taken the boat out for some months now hence the approx !, pretty sure it is right though and the speed at 3700 - 4000 RPM is approx 25 - 30 mph vs approx 10 mph @ 3000 RPM.

Thanks

Jamie

shrew · 01-29-2015, 02:40 PM

Quote:

Originally Posted by Maxum2300scr

Hi Shrew,

As mentioned in my previous post it is around 4600 to 4700 RPM @ WOT trimmed out with no tab @ approx 38 mph as previously mentioned I have not taken the boat out for some months now hence the approx !, pretty sure it is right though and the speed at 3700 - 4000 RPM is approx 25 - 30 mph vs approx 10 mph @ 3000 RPM.

Thanks

Jamie

Apologies, I had gone back to the first post and overlooked the second. I would not increase pitch based on these numbers. Your numbers would indicate you are propped perfectly for that engine and boat setup. If you increased pitch in order to achieve your target numbers it's going to be a pig climbing out of the hole and put tremendous load on the entire system unnecessarily.

Maxum2300scr · 01-29-2015, 04:45 PM

Quote:

Originally Posted by shrew

Apologies, I had gone back to the first post and overlooked the second. I would not increase pitch based on these numbers. Your numbers would indicate you are propped perfectly for that engine and boat setup. If you increased pitch in order to achieve your target numbers it's going to be a pig climbing out of the hole and put tremendous load on the entire system unnecessarily.

Already a bit of a pig for hole shot, I also feel the WOT reves are good and I am quite happy with the top end speed, I just want to get out of the hole a bit better any idea's ??

mmwjr · 01-29-2015, 04:58 PM

In post #5 you said you don't really use the trim tabs, these greatly help get the bow down and the boat on plane. Also try shifting some weight forward, coolers into the cabin, ...

forbes210 · 01-30-2015, 02:24 AM

Exactly what Mike said. Usually when I'm getting on plane with my 2500 scr I'll keep the outdrive all the way down and will drop the trim tabs about 70% down. As soon as it will get on plane I'll trim up the outdrive just a bit and bring the trim tabs up to about 20%. I drove few bigger boats and played with the trim tabs on them. My impression was that the bigger boats weren't that sensitive as far of trim tabs position. In my case trim tab set up got huge impact on getting on plane and also cruising. Weight distribution also plays a big role on boats our size.

Maxum2300scr · 01-30-2015, 05:15 PM

Quote:

Originally Posted by mmwjr

In post #5 you said you don't really use the trim tabs, these greatly help get the bow down and the boat on plane. Also try shifting some weight forward, coolers into the cabin, ...

Hi Mike

I have tried people in the front of the boat and all the gear and yes it does make a difference, although I am taking the boat for a service soon and a fresh coat of antifoul. I think I will get them to check over the trim tabs as well, I am sure one is a bit sticky, maybe this is why I did'nt use them that much last season.

I have also been speaking to a freind of mine, who is telling me that maybe this is down to the propeller being for a sport boat and not really designed for a good hole shot but actually top end speed ?, he thinks the weight of my boat might be causing a issue with this type of propeller.

Maxum2300scr · 01-30-2015, 05:23 PM

Quote:

Originally Posted by forbes210

Exactly what Mike said. Usually when I'm getting on plane with my 2500 scr I'll keep the outdrive all the way down and will drop the trim tabs about 70% down. As soon as it will get on plane I'll trim up the outdrive just a bit and bring the trim tabs up to about 20%. I drove few bigger boats and played with the trim tabs on them. My impression was that the bigger boats weren't that sensitive as far of trim tabs position. In my case trim tab set up got huge impact on getting on plane and also cruising. Weight distribution also plays a big role on boats our size.

Hi Forbes,

Thanks for your input I like the 2500 SCR nice boat not too big to take out with just a couple of us, maybe I will trade up one day. I have replied to Mike and think I will try your set up when I take it out after i have had it serviced. Just out of curiousity what size motor or motors are you running and how does it go.

mmwjr · 01-30-2015, 08:56 PM

The prop size you have sounds tight for at boat, if the tabs do not help enough you could drop one pitch this will increase WOT by about 200 rpm

forbes210 · 01-31-2015, 12:18 AM

Quote:

Originally Posted by Maxum2300scr

Hi Forbes,

Thanks for your input I like the 2500 SCR nice boat not too big to take out with just a couple of us, maybe I will trade up one day. I have replied to Mike and think I will try your set up when I take it out after i have had it serviced. Just out of curiousity what size motor or motors are you running and how does it go.

Its a single mercruiser 5.7 250 hp with bravo 3 drive. In my opinion this engine works really well with this boat. Its my first boat so I don't have a lot of experience with other but it feels like theres always more power then you need. Using trim tabs I can get on plane in no time and without gear and extra weight I was able to hit 40 mph. In my opinion 2500 scr offers a lot in this size/price range. Also its very descent on gas since cruising around 25 mph I'm burning not more then 10 gal per h. I bough it 2 years ago and today I can't imagine my life without it

I think I'm addicted

Maxum2300scr · 02-01-2015, 06:20 PM

Quote:

Originally Posted by mmwjr

The prop size you have sounds tight for at boat, if the tabs do not help enough you could drop one pitch this will increase WOT by about 200 rpm

Hi Mike

I have been looking for answers on the net aswell and it seems that a 4 bladed prop should give me what I am after, this also recommends that I drop 1 pitch size, this sound promising. I can't wait to get back out on the water I've got alot of things to try this season. The weather has taken a bit of a turn for the worst at the moment it's a bit stormy with cold temps and some snow. I wont be trying it very soon.

Jamie