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Old 05-18-2017, 02:21 PM   #1
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Default 2000 2800 SCR Props.. What do you use?

First off, hello to all. Just signed up to the Maxum Forum..

Need some help here.....

Purchased a 2000 Maxum 2800 SCR with twin 4.3 carburated engines with the Bravo 2 drives.

Took it out for sea trial after delivery and only in the upper 3 thousand range at WOT.

Got a hold of the dealer and was told it had the factory 18.25 x 19 props. They were repaired at one time. (aluminum)

Well I go on Mercruiser's site and they tell me I need 17.25 x 25 props

My question is to all our 2800 and 2900 SCR owners with the twin 4.3's.... Carbureted or injection.

Please tell me what props you are running??

FYI... I work in the marine field, mostly Volvo Penta, and know all that is involved in reaching WOT RPM. My issue is definitely the props. Only thing I have left to verify is a master gauge on the vessels Tach.

Thanks in advance..
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Old 05-18-2017, 02:45 PM   #2
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I have same boat same power and run 19 you wil never be able to run 25. if you only get 3000 rpm @ wot you may have other problems. I get 4200 to 4400 rpm both motors
hope this helps
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Old 05-18-2017, 02:57 PM   #3
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Most mercruiser Inboards (and I/O's) are rated for a max RPM range of 4400 - 4800 rpms. You really don't want to be under 4400 rpm's as that would indicate that you are either overpropped for the boat, or overpropped for the weight of gear and passengers.

"upper 3,000" is a little vague 3700? 3900? 1" of pitch should change the rpm by approx. 200. Increase Pitch and decrease RPM's (and vice versa).

If you are already overpropped, then going to from 19" of pitch to 25" of pitch would be worse. Modifying prop diameter will come into play, but that adds an additional variable that significantly complicates the calculations.

I ran through the calulator and I'm not coming up with the same numbers you're coming up with.

What is your BII gear ratio? Vessel weight? Overall dimensions?
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Old 05-18-2017, 04:32 PM   #4
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First off thanks for the replies..

The bravo's are 2.2 gear ratio.

I was around 3400 RPM on the sea trial (quick one) trimming I could have most likely got to 3600. (I have to master gauge these coils so I can be exact.)

I would settle on 4200 but not under that.

Here are the ways I was fooling around on the Mercury site.

Step one cruiser, ..... step 2 ....I chose mid range cruise... Step 3..... Engine info 2000 4.3 carbureted....on the pitch selection page I did the following:

Length... I used 28 Ft all the way to 30ft...... Result: 17.25 x 25 or 17.5 x 23

Method by weight: 7000 (says without engines and CANNOT put a weight in under 7000) 700 pounds for passengers and gear. Fuel 100... Result: 17.25 x 25
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Old 05-18-2017, 05:18 PM   #5
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First I would verify what props are on the boat as dealers are not always correct on what they say. You need to decrease pitch to get the rpms up. Not sure why the calculator is giving you that result but 25" pitch on 4.3's is a killer.
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Old 05-19-2017, 02:08 PM   #6
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Step #1: Cruiser
Step #2: Overall Good Performance (Altitude = No)
Step #3: Mercury; Sterndrive; 2000; 2 engines; V6; 4.3L; Bravo II (2.2)
Step #4:

PERFORMANCE:
Pitch: 19
WOT (RPM): 3500
Top Speed: 22
Results: 19.5 x 15

LENGTH:
Length: 30 (ft)
Results: 17.5 x 23 or 19.5 x 22.5

I'm not getting anywhere near a 25" pitch.

Is the bottom clean and smooth, or is the bottom paint cratered like the moon? Is the vessel overloaded with people or gear?
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Old 05-19-2017, 07:48 PM   #7
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Just so everyone knows........ Tachs were switched for 8 cylinder and not 6... All good.
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Old 05-19-2017, 09:54 PM   #8
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Quote:
Originally Posted by Bluebear View Post
Just so everyone knows........ Tachs were switched for 8 cylinder and not 6... All good.
Interesting, were they replaced?
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Old 05-20-2017, 01:37 AM   #9
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There is a switch on the back of the tach's to use them for 4, 6, and 8 cylinder engines.
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Old 05-20-2017, 04:21 AM   #10
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Quote:
Originally Posted by Bluebear View Post
There is a switch on the back of the tach's to use them for 4, 6, and 8 cylinder engines.
Yes I know that but I doubt there were set wrong from the factory so my question is how did they get changed. If the tachs were replaced the installer did not set them properly.
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