Help I need a new prop

[nitrosteve]

Current setup:
1986 Mark Twain MTB175

3.0l 140hp Mercruiser
1.98 ratio I think

Current prop:
13 3/4 x 19 Aluminum 3-Blade
(I tried a 14.25x 19 but it just barely touched the tab when I spun the prop)

Dry Weight:
2200lbs

Speed/RPM @ WOT:
36mph/4500 (no GPS) me by myself.

Typical Load:
600# people and gear
15 gallons of fuel
w/ 700# of passengers and gear

I just want it to perform better all around without breaking the bank. I typically will never have less then the load listed. I pull tubers on occasion but just mainly cruise at 25-30 mph. I don't want to sacrifice any top end as I feel its alittle slow the way it is. I am expecting a miracle prop

Thanks for any insights
Happy Boating

 

[Rocky_Road]

Re: Help I need a new prop

Change the trim tab, and run that 14.25x19...you'll love it!

Happy boating!

 

[hwsiii]

Re: Help I need a new prop

SteveIboats 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 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 and turn the motor until the tape lines up with each other, 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
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. If you do not have a tach you can buy a Tiny Tach for $ 50
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

 

[nitrosteve]

Re: Help I need a new prop

I haven't forgot this I just had a sinking feeling my foam is all wet and what was the sense in getting all this info. I will wait till I get the deck replaced and the wet foam out before I take on a prop replacement.

 

[180shabah]

Re: Help I need a new prop

Pretty sure everyone will still be around when you're ready.

 

[nitrosteve]

Re: Help I need a new prop

Ok so I got rid of Mark twain but put the motor in this boat. Thanks for your help.
1. 1998 180 Monterey
2. 18ft,7ft 9 beam, dry weight 2100lbs
2a.190hp
3. 3 people, 20 gallons
4. Mainly cruising at 30 mph or faster.
5. I wouldnt consider it a deep-v but I don't know the dead rise
6. 1987 3.0 140hp Mercruiser I/O wrong year I know but it fit.....
7. 140hp Alpha one gen 2 2.0 ratio
8. 4400-4800
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. ?
11. no
12. 13.75 x 19 Aluminum not sure the maker
13. 4950 rpm 42.1 mph GPS 3 people 10 gallons
14. Sea Level
15. Motor is in perfect working order.
16. Prop has been on boat for 6 months
17.would like higher cruising speed at less rpm. I would also like to lower the wot rpms into the correct range. It has very little damage mostly cosmetic.
18. See 17
19. Hmmm not sure I will get a chance to do this. I can tell you 30 mph with 3 in the boat 10 gallons of fuel is about 3700-3800 rpm. 35 is right at 4200rpm.

On a side note I have a 14x17 vengence SS prop that seems to take alot more positive trim and raise the bow. My current prop planes out well but you cannot trim it up near as much without it washing out. Not sure why this is. Thanks for your help..