Prop help

rdwsdw1

Cadet
Joined
Aug 4, 2009
Messages
6
I was hoping someone here could help me with a question on my prop. I am running a 1990 18' Nitro with a 1990 Johnson 150 HP motor. The prop that I bought it with is a SS 13 1/4 X 25PP prop, I dont know the brand.

The problem I am having is this...I am a fairly large guy. With my wife and the livewells full I have a lot of trouble getting this boat on plane. When I try to plane out it will not push more than 4000 RPMs. If she moves forward we can get it to plane out and run 5500 rpms and seems to run pretty good then.

I am not too interested in top end speed, I am much more interested in hole shot for when we take the kids tubing. Could this prop be part of my problem? What prop (size and pitch) would you recommend me replacing it with if it is?

Thanks
 

hwsiii

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

Rd, welcome to Iboats prop forum and we will try to help you as much as we can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can, if you would prefer to not go to this much trouble there are other people who will 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 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 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
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Prop help

Let's double check the prop size. Most 13 1/4" props are for a 4 1/4" gearcase not a (V6) 4 3/4" gearcase. If someone has rehubbed a V4 prop to work on your V6 that may be the main issue.

Most likely you'll end up with 2 props. One for normal running and one for water toys but you'll need a spare anyway.

Right now check the diameter of your existing prop. If it is indeed a V4 prop then we need to test a V6 prop to get a good baseline.
 

rdwsdw1

Cadet
Joined
Aug 4, 2009
Messages
6
Re: Prop help

H and Dhadley

Thank you both for responding. This is my first boat and I apologize for my ignorance as I am still learning. Dhadley I will answer you first (since its much shorter) and H I have answered as much of your questionarrie as possible and will post below.

I double checked the prop and I believe it is a shooter (only thing it says that refers to a make or model) it does say 13 1/4 which I verified with a tape measure. It also says 25 PP which I assume is the pitch. The motor is a V6 150 HP Johnson, whether it was rehubbed or not I cannot say but if there is a way to check Ill be happy to do so.

H the responses to your form are below -

1. Year, make and model of boat
- 1990 Tracker Nitro 185TF
2. Length, width and base weight of boat, look for boat decal on back of boat:
- Length 18'10" Beam 7' 3"
2a.What is the recommended HP for your boat
- 150hp to 185 hp
3. Number of people and gallons of gas normally on boat
- 2 adults (sometimes additional 2 teen girls) 20-30 gallons of fuel
4. What do you use the boat for
- Primarily fishing but occassionally to pull a tube.
5. Is it a Deep Vee and if so how many degrees of deadrise
- Bassboat
6. Year, make and model of motor
- 1990 Johnson 150HP model TJ150SLESB
7. HP and gear ratio of motor IMPORTANT
- 150 HP 1.85:1 (believed to be)
8. Manufacturer?s recommended Wide Open Throttle (WOT) range:
- 4500 - 5500
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
- excuse my ignorance but Im not sure what that is.
10. Is it a bass boat or does it have a pad bottom
- bass boat
11. Does it have a hydrafoil, dolefin or trim tabs
- Hydrofoil
12. Make, model, diameter, pitch and whether SS or aluminum prop
- On the prop itself it says - 13 1/4, 25PP, Shooter, and it is stainless steel
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
- Best RPMs I can get pre-planing is about 4000, if/once I get on plane it will hit around 5200. I do not yet know the speed but will test that tonight.
14. Are you at sea level or a higher elevation, give us the elevation in feet.
Roughly at sea level.
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
- I have replaced the fuel filter, fuel pump, fuel lines, spark plugs, and replaced the gas in the tank. I will be checking compression and spark this weekend and I plan to order the kits to rebuild the carbs soon (20 year old motor figure it wouldnt hurt). I have only owned the boat for 2 weeks so I cannot answer what was done prior to my obtaining it.
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
- I do not know how long the prop has been on the motor. A post I placed on another board about cleaning it indicated it may be the wrong prop for this boat/application.
17. Does the prop show any damage that you can see
- Other than a few scratchs and very minor nicks nothing major. I can post a picture if that helps.
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
- I am a fairly large guy but even with just me in the boat it can struggle to get on plane. I do not care so much about top end speed, I do care about getting it on plane as easy/quickly as possible. Partly for tubing but mostly because I dont like having a difficult time seeing whats in front of me while trying to get on plane.
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.
- I will be happy to do this.
 

hwsiii

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

Rd, would you take a closeup picture of the prop and where it enters the lower unit so we can see if it is in actuality a V4 hub and not a V6 hub. Like Dhadley said if it is a V4 hub that could definitely be the problem even though it has 4 blades, and I have found him to be right regularly.


H
 

rdwsdw1

Cadet
Joined
Aug 4, 2009
Messages
6
Re: Prop help

Are these what you are looking for? If you need even closer I can do that too.

2mqm454.jpg


15n3k05.jpg
 

hwsiii

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

Dhadley was right as usual, you have the wrong size for your gearcase and that is your problem. I am going to step out of this and let Dhadley get you setup right. He will be better at this than I am for top speed and performance with the right prop on your boat.
I am pretty sure he will see this tomorrow morning and get with you then.



H
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Prop help

Looks like someone went to a lot of trouble to get a V4 prop to fit on a V6. No problem, we just need to get a V6 prop on there to establish a good baseline so Hw can run & record the numbers. The Nitro is a pretty darn good design so picking a style is no big deal.

Based on your intended use specification I'd look real hard at something like a Turbo Ultima 4. That boat likes props with good lift which the U4 has a lot of. If we were going for top speed I'd look at the Lightning.

See if you can borrow a V6 prop in decent shape to test. Something in the 21 to 23 range if possible. At this point we're not worried about top speed but rather just good info. If you need help finding a V6 prop to test let me know. Maybe between a few of us here can come up with something to try.
 

rdwsdw1

Cadet
Joined
Aug 4, 2009
Messages
6
Re: Prop help

Sorry it has taken so long to respond, it was a long week at work. I took the boat out this weekend (same prop) and ran some numbers with the GPS. At 5000 RPMs I was hitting about 46 MPH trimmed out.

Does anyone know if a Marine dealer would usually have props to try out before you purchase? Otherwise I will have to wait a couple weeks before I can buy one of the suggested props.
 
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