Re: How much would this effect performance?
3 or 4 or 5?? Just from what I've read here.
Props seem like photography. There a few variables that yield infinite combinations.
The prop that I got with the boat is chewed, so I'm looking to buy a new one as a starter.
I'll provide the most information I can at this time to complete your questionaire:
Iboats Boat and Motor Info
1. Year, make and model of boat
1990 Glastron Sierra 175
See...http://forums.iboats.com/showthread.php?t=365799
2. Length, width and base weight of boat, look for boat decal on back of boat
(the decal isn't readable) 17', I believe 2900 lbs
2a.What is the maximum recommended HP for your boat
Don't know recommended...it has a 4.3L, Alpha 1 outdrive
3. Number of people and gallons of gas normally on boat
50% - 2 adults and 1 child and lets say...15 gallons of gas (500-600lbs)
50% - 4 adults and 3 children and 15 gallons of gas (1000 lbs) (max capacity is 1050)
4. What do you use the boat for
Currently my son is 3 so we're not big into water sport just yet, but pull a tube and some skiing when friends visit.
50% - cruising, site seeing
50% - mostly tubing and some skiing
5. Is it a Deep Vee and if so how many degrees of Deadrise
No, not Deep Vee, more like a Mid Vee
6. Year, manufacturer and model of motor
1990 4.3 L, Mercruiser, Alpha 1 outdrive
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 flywheel 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
185 HP, Compression ratio is 9.3:1 (but I don't think that's what your looking for?)
The decal that states 'stern drive unit gear ratio' read: 184R (but that's not a ratio so I don't know what that represents exactly)
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
4400-4800 RPM
9. Anti-ventilation Plate height above the bottom of the transom of boat if it is an outboard in inches, use a straight edge or a board under the keel and sticking out to the anti ventilation plate for a reference, and take about 4 pictures for us to see.
10. Is it a bass boat or does it have a pad bottom
no
11. Does it have a hydrafoil, dolefin or trim tabs
no trim tabs, no hydrafoil...dolefin - not exactly sure what that is - there are fins on the outdrive, I call them "whale tail"...same thing?
12. Manufacturer, model, diameter, pitch, number of blades and whether SS or aluminum props.
IMPORTANT
Aluminum, Identifying numbers are 48-78120-19, diameter 13"
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 less than $ 50
RPM ___________ Speed (GPS)___________ No. of people ____________ Gal. Gas ________
unavailable
14. Are you at sea level or a higher elevation, give us the elevation in feet __________
sea level
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way by only using the control on the console, checked compression, looked at the plugs and checked spark, is the bottom of the boat clean and barnacle free, and have you checked the Tachometer against a mechanics tach, all of the foregoing could be the reason your prop is not attaining full RPM.
unavailable, lets assume it's running normally as we're not problem solving but looking for best recommendation at this time.
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop.
Came with boat, unknown history, damage to blades
17. Does the prop show any damage that you can see
yes
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
Unavailable. As a starter prop to do the actual performance tests I'm looking for a 'middle ground' prop. Aluminum, as it less expensive and may be replaced when the tests are done.
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.
1. 3000 RPM
2. 3500 RPM
3. 4000 RPM
4. 4500 RPM
5. 5000 RPM
6. 5500 RPM
7. 6000 RPM
Unavailable
I hope this information is sufficient. I'm not entirely sure on the gear ratio, can someone enlighten me if I'm correct?
Thanks for your time, truly informative!
