Prop help

GalaxyBR

Cadet
Joined
Sep 11, 2009
Messages
8
I believe my boat is under proped boat was up powered by PO from 3.0I4 to 4.3v6 out drive was replaced with a 165 alpha1. makes 35mph@4300rpm with 2 adults on board. I feel this boat should run faster i know its a large heavy boat but don't know. any insight would be helpfull

1) Performance issue you are trying to correct. what is stock/OEM size
2) Current prop manufacturer, model, aluminum or stainless and as a minimum. currently has stainless manufacture unknown
3) Current prop diameter and pitch (required). currently 14x19
4) Wide open throttle RPM and speed with an average load (very helpful) at 4300rpm with 2 adults makes 35mph
5) Engine/drive make, model, year, and HP mercruiser 4.3v6 w/mercruiser 165 1.84r ratio SN 0B754513
6) Boat make model, year, length and weight 87 Galaxy BR 18.5ft weight unknown
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Prop help

Galaxy, you are currently showing a prop slip of 17% and that is very high for a good SS prop. You are running close to manufacturers recommended RPM range which is probably about 4,600 RPM at WOT.
If you will fill out this form I will try to help you.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing then do the same thing on the motor and turn the motor until the tape lines up with each other on the prop, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for $ 50
RPM ___________ Speed ___________ No. of people ____________ Gas ________
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.


H
 
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