Volvo Penta 5.0 FL Prop

[mycirus]

I can only get about 41 mph (GPS) out of my 5.0 with an SX drive. I have a 20 pitch 4 blade prop. I would like a little more top end. What prop should I have? What do other people have on thier boat? My boat is a 95 Larson 19 bowrider. I think the previous owner changed the prop. I am not sure what prop I am supposed to have. Any ideas?

 

[ramster]

Re: Volvo Penta 5.0 FL Prop

What is your rpm at top speed? Are you trimming the drive up once under way? I think a 19 with a 5.0 should run close to 50 mph.

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

Im getting 4300-4400 out of it WOT. I was expecting around 50 too. Just had the heads rebuilt on it. When I bought it it was backfiring and had no compression in Cly 2. Its running mint now. I was just expecting a little more performance.

 

[ramster]

Re: Volvo Penta 5.0 FL Prop

Is your motor a 2 barrel carb? What was the problem with the heads? I'm thinking this is an engine issue not a prop issue. I have an 04 Glastron SX 195 W/a 220 HP 5.0 and I could spin a SS four blade 20" to 4700 RPM@ 52 MPH, now with a four barrel I get around 4900@ almost 55MPH. Unless it's a real agressive prop like a Stilletto, or Turbo you should be able to spin it faster, to me that say's your down on power.

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

The heads had a burnt valve and rebuilding them found a crack in the one with the burnt valve. I had new valves put in them and got them back in. I did some testing yesterday. Still cant get it about 40 MPH. At full throttle the RPM is about 4300, but if I trim it up I can get it up to 4700 but it just slips, doesnt make the boat go faster. Do I need a 3 blade prop? A SS one? Its a black 4 blade right now. Just trying to figure out what this boat came with from factory. Anyone have a Larson SEI 19 with a 5.0 FL?

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

Anyone?

 

[hwsiii]

Re: Volvo Penta 5.0 FL Prop

My, if you will fill this form out I 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 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 a c ross 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, 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
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

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

1. Year, make and model of boat 1995 Larson SEI 19
2. Length, width and base weight of boat, look for boat decal on back of boat 19 feet, 7.5 beam, weight??? Its night time right now
2a.What is the maximum recommended HP for your boat unknown
3. Number of people and gallons of gas normally on boat 3 to5 people 25 gallons
4. What do you use the boat for cruising, tubing, knee boarding
5. Is it a Deep Vee and if so how many degrees of deadrise bowrider, reg Vee I guess?
6. Year, make. manufacturer and model of motor 1995 Volvo Penta 5.0 FL
7. HP and gear ratio of motor IMPORTANT 190 HP
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape a c ross 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 4500 RPMs
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 no
11. Does it have a hydrafoil, dolefin or trim tabs has a fin, on back of outdrive
12. Make, model, diameter, pitch and whether SS or aluminum prop Alum, 20 pitch 4 blade
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 From GPS, 40 mph 4200 rpm, can trim up and get more rpm, but speed does not increase
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, 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 fresh tune up and heads rebuilt
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
17. Does the prop show any damage that you can see no
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 more top speed
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.2 people WOT 40.5 MPH, 5 people WOT, 38-39MPH, 3000 RPM is about 26 mph or so.....


Everyone loves pics...

 

[hwsiii]

Re: Volvo Penta 5.0 FL Prop

I am showing a 17% prop slip for your boat with a 1.66:1 gear ratio, and that has to be wrong, will you verify the gear ratio please.


H

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

Online I was able to narrow it down to these 2, 2.30:1; 1.95:1 Its raining cats and dogs right now.

 

[rodbolt]

Re: Volvo Penta 5.0 FL Prop

to find the ratio on the SX drive look for the tag on the port side about the middle of the drive. takes the guess work out of it.
the 1.6 ratio was widly used with v8 motors.

 

[ramster]

Re: Volvo Penta 5.0 FL Prop

20 or 21 should be the fine for that boat, a 5.0 should be more than 190 HP, is it a 2 barrel carb? You said discovered a crack doing the valve job, was the head replaced? I still think there is an issue with the motor. If it is an Aluminum prop 14X20" is most likely a Vortex, or Alpha Four, they are not very aggressive props, you should be able to rev either of those higher.

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

Thanks for telling me where to find the ratio, it is 1.66. The prop is a Quicksilver 4 blade and has the numbers J 14 X 20 P 2186P20 stamped on it. It is a 2 barrel carb, and yes, I bought a replacement head for it. When it was messed up it was backfiring like crazy at higher rpm, now its running mint, except that I cant get over 40 in it.

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

I am showing a 17% prop slip for your boat with a 1.66:1 gear ratio, and that has to be wrong, will you verify the gear ratio please.


H

So it is the 1.66, why does that have to be wrong? What needs fixing?

 

[hwsiii]

Re: Volvo Penta 5.0 FL Prop

The reason I said that was beause you are using a 4 blade prop and I didn't think that you should have that muh prop slip. But I see from the numbers you posted that you are using the QS Diamond 4 blade and they have very little blade surfae area, and that is why the prop slip is so high. You need to buy a Solas Amita 4 blade 18" pith prop to derease your prop slip and get your RPM very lose to maximum of 4,600 RPM. You might pik up 1 or 2 MPH but I am not positive. It is always best to be able to reah maximum RPM, and that way you don't lug the engine.
My numbers show you an't get over 44 MPH no matter what prop you put on it.

Prop hange

Prop Slip

H

 

[mycirus]

Re: Volvo Penta 5.0 FL Prop

Awesome, thanks.

 

[hwsiii]

Re: Volvo Penta 5.0 FL Prop

You are very welome My, and by the way you have a beautiful boat. Please ome bak and give me the WOT RPM and speed for my database.


H

 

[harojs]

I thought in general a 3 blade prop is better for top end. 4 blade gives better power and holeshot.

Is that not generally true?

I would be interested in submitting my specs for analysis as I am looking to re prop to improve my cruising range.

Is the doctor still around?

John