3.0 mercruiser alpha 1

[wid0wer]

okay not sure if i should post here or not,
question i have is what speed should i be going in my 1991 18' Thompson calae 175 mercruiser 3.0 with alpha 1
on water at WoT 4800rpm i go 30mph according to gps, i am not sure if this is all faster i should go or what , ( any help would be great thank you

 

[alldodge]

Should be in the prop section, a Mod will be along and move it later for ya

In order to know if your numbers are good we will need two more numbers, your drive ratio and the prop pitch

 

[wid0wer]

Only numbers on prop are Michigan 031024 I typed in numbers in google and found

• Part(s): #031024
• Manufacturer: Michigan Wheel
• Brand:Michigan Match
• Material: Aluminum
• Diameter: 14 - 1/2
• Pitch: 17
• Blades: 3
• Rotation: Standard (Clockwise)

, where do I find drive e ratio?
just a guess but since it is a 1991 (I am not currently home at the moment ) https://www.seilermarine.com/info/me...atio-chart.php but I am guessing 1.94 gear ratio

3 Liter

130

3.0/181

4

1.94

20-24

1991-2005

 

[thumpar]

The ratio show be 1.94/2.0. It might be stamped on the side of the drive. You could try a 19 pitch stainless prop but you will probably lose some holeshot.

 

[wid0wer]

thank you for your help but is that the speed my boat should go , reading other similar forms to mine people with similar boats and motors are running around 40 mph

 

[stonyloam]

At 4800 RPM, assuming 17 pitch prop, 12% slip, 35 mph.

 

[wid0wer]

At 4800 RPM, assuming 17 pitch prop, 12% slip, 35 mph.

so is there anything I should check at 4800 I am only doing 30 mph

 

[thumpar]

Are you trimming out?

 

[alldodge]

so is there anything I should check at 4800 I am only doing 30 mph

Things can cause you to loose speed are:
Hull is not clean
Prop is damaged (ding, dent, blades not true)
Improper trim
Hull is heavy (water soaked, or to much gear)

 

[wid0wer]

Things can cause you to loose speed are:
Hull is not clean
Prop is damaged (ding, dent, blades not true)
Improper trim
Hull is heavy (water soaked, or to much gear)

Yes I was at 28mph according to gps at 4800 t messed wit trim up and got to 30mph. The bottom has a slight bit of alge on it

 

[Starcraft5834]

If your running WOT at 4800, that would suggest your pitch is in the ballpark and correct... 18ft heavy boat perhaps water logged... I run a 1987 3.0 on my 20 ft cuddy, deepV,, it's heavy....with 4 blade.. 16p...I get that going just over 30 myself.... every boat is different... if your prop is bent, dinged up.. new one will get u a bit faster

 

[Bondo]

The bottom has a slight bit of alge on it

Ayuh,.... It takes very little sealife to seriously slow yer boat,.....

Zebra mussels are Bad this year, I'm down to 29/ 30 mph, from a normal 42/ 43 mph,....