Prop help

[yomamaho]

I have a 1997 Bayliner trophy 2352. I have a broken 48-832830-c1 prop which i think is 14 1/2 x 19. I would like to get better all around performance from the boat. To me it seems the boat could have the wrong prop since the day i bought it (hard to handle at higher speeds and top end is only 30 mph or so). i think the boat weighs near 4500 lbs and has 220 hp merc. I've been reading about props for 2 days now and my head is about to explode. I'm leaning toward a SS 3 blade or 4 for better performance. Anyone have this boat? Any help would be appreciated, thank you.

 

[hwsiii]

Re: Prop help

Yomamaho,welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information, and most other people who are trying to help you will need the same information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the exact prop you need for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM.

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
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
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Does it have a hydrafoil or trim tabs
11. Make, model, diameter, pitch and whether SS or aluminum prop
11. WOT RPM and speed from prop, how much gas and how many people in boat for test data

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

 

[yomamaho]

Re: Prop help

Hi hwsiii, thanks for responding. i will give you what i know (specs for my boat are hard to find)
1, 1998 bayliner trophy 2352 ( i wrongly put 97 previously)
2, 23 ft 5 in length, 4740 lbs dry weight, 2ft 10 in draft
3, 600- 700 lbs in people on most trips, 100 gallon tank i like to keep close to full
4, used for fishing in sandy hook to mudhole (nj)
5, deep vee, do not know deadrise
6, 98 mercruiser 5.0L, 220 HP with alpha 1
7, i do not know gear ratio
8, WOT is 4400 to 4800
9, hydrofoil and trim tabs are installed
the prop i have now is broke, its an aluminum 14 1/2 x 19. i do know i was running in WOT parameters last year with my fishing buddies on board. I would love to give you more test data but i need to get a new prop to do this. starting from the prop i have now i am thinking cupped SS at 14 1/2 X 18. i just think the boat could handle better than it does( at higher speeds i have to play with the trim tabs constantly to stop leaning left and right). it also loses traction at mid speeds. once again thank you for whatever you can do for me.

 

[hwsiii]

Re: Prop help

Yomamaho, get rid of the hydrafoil, that is the most likely cause for your problems of the boat leaning to the right and left and you having to continually use the trim tabs. A hydrafoil picks the boat up in the middle of the boat and that tends to make the boat able to fall either to the left or right depending on conditions of waves, steering or people moving in the boat. Think of it as a seesaw that kids get on, when the center of balance is the center of the boat it will very easily fall to the left or right with very little weight movement needed to make that happen and steering can even do it, especially on deeper vee boats. Trim tabs work on the outside edges of the boat so they help stop this type of behavior. It also will make the boat go slower at higher speeds because of the excess drag created, especially on inboard outboards because of how deep they are in the water. Take it off and you will see less need to use the tabs constantly and also you will see a top speed increase. After we get you propped better take the boat out and run it from 3,000 RPM up to WOT RPM and write down the speed and RPM for each 500 RPM increment to WOT RPM with the hydrafoil on it. Then pull the hydrafoil off and do the same thing again and you will see what I mean. Be sure to run in two 180 degree opposite directions and add the two numbers together and divide by two so we can account for any currents.
In the meantime lets try to get the right prop for your boat.

Hydrafoil versus Trim Tabs

H

 

[yomamaho]

Re: Prop help

Thanks for this advice, i will definitely try this when i get out. any idea on what prop i should go for. i was thinking the michigan ballistic ss 14 1/2x19.

 

[hwsiii]

Re: Prop help

I can't find the gear ratio for your outdrive. Look on the outdrive and see if you can find it, if not get the serial number for the outdrive and call your local mercruiser dealer and ask him what it is.

H

 

[yomamaho]

Re: Prop help

I have found my serial number (OL192721). i have made a few calls and a few emails to no avail yet. One would think that mercruiser would list this information someplace on their web site, NOT. When i get an answer i will post it immediatley. thank you

 

[yomamaho]

Re: Prop help

Mercruiser got back to me with 1.62:1

 

[hwsiii]

Re: Prop help

Great, I will run some numbers for you.

H

 

[hwsiii]

Re: Prop help

Yamomaho, I am finding a problem with your RPM, speed and gear ratio. If I use the 1.62:1 gear ratio and you said the boat was running within recommended RPM which is a minimum of 4,400 RPM with a 19" pitch aluminum prop and it only runs about 30 MPH (I used 32 MPH) I am showing a prop slip of 35%, which is exceedingly high. If I use higher RPM it only increases the amount of prop slip.
Something is wrong, I don't know what it is but something is real wrong. Could you be remembering wrong data.

Real Prop Slip

H

 

[yomamaho]

Re: Prop help

Yes its very possible that my memory is wrong, I'm out there fishing thinking about fishing. the boat always ran good and got me from point a to point b. So i never really concerned myself with the statistics of the boat until now. whats your thoughts? maybe my speedometer is off, when i get out i can switch to GPS speedometer.

 

[junior1113]

Re: Prop help

Yes its very possible that my memory is wrong, I'm out there fishing thinking about fishing. the boat always ran good and got me from point a to point b. So i never really concerned myself with the statistics of the boat until now. whats your thoughts? maybe my speedometer is off, when i get out i can switch to GPS speedometer.

speedos can be off 10mph easy. gps is true speed. speedos can be adjusted in most cases

 

[yomamaho]

Re: Prop help

I still need to figure out a prop to start off with. Hopefully we come up with a good choice. when i get out i'll write down the data, post it and see if I need a different prop. I just hate to spend money and have to go buy a different prop. I do not really know anyone where i can just try different props.

 

[junior1113]

Re: Prop help

if i were in your shoes i'd buy a cheap alluminum 4 blade 17 pitch and see.might be the ticket or youll have a starting point and a good spare. get that foil off of there.

 

[hwsiii]

Re: Prop help

Yomamaho, lets go through what we KNOW.
1. You did have a 14.5 x 19" aluminum prop
2. Mercruiser says your drive is 1.62:1
3. Your boat weighs about 6,100 pounds with 75 galloons of gas and 4
people with some ice and gear
Under these guidelines my program says we need a 17" pitch prop and that the 19" was too high a pitch. Paul you are right.
If you have enough money for a spare prop that cost about $ 105 my recommendation is for the Solas Amita 4 in 17" pitch.
Iboats
Price: $103.99
You Save: $43.01
Compare: $147.00
Discount: 29.3% Off
Propeller Specifications:

SKU:#1513-145-17
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 14 - 1/2?
Pitch: 17?
Blades: 4
Rotation: Standard (Clockwise)
Then we can find a 4 blade SS to fine tune your speed and handling with the tests that we run with this.

Here are my numbers with the information that we know for right now. I am not saying you will reach 40 MPH because most heavier higher vee boats with smaller motors don't usually reach their full potential because of weight ratio and prop slip and you won't be at the maximum RPM, but you should reach at least 34 with the right prop.

Prop Picker

H

 

[yomamaho]

Re: Prop help

OK Kids, we"ll try this, go to the numbers and see what we come up with. sounds good to me. i'll report back with numbers.

 

[hwsiii]

Re: Prop help

I will be here. LOL

H

 

[yomamaho]

Re: Prop help

One more question? Why the 4 not a 3? doesn't the extra blade just cause drag?

 

[hwsiii]

Re: Prop help

Yes it does create more drag than a 3 blade but it also has more blade surface area than a 3 blade and with a 6,000 pound deep vee boat and almost a 30 pound power to weight ratio that is a major plus having the extra surface area to carry that load. That is the reason for my recommendation of a 4 blade prop.

H

 

[yomamaho]

Re: Prop help

OK thanks