We get soaked on plane - Prop Problem??

[scrkw2000]

We've had an aluminum 1999 fisher deckboat for a few years now and love the boat, but only on very calm water. If there's even mild chop waves tend to splash over the bow when on plane and soak the occupants. I think its a hull design flaw, but I was told that perhaps its a prop problem. So I did some research and tried various pitch/blade combinations and although some improved performance, none seemed to have the desired effect which is to hold the bow higher out of the water while on plane. The boat does all we wanted it to do. It pulls hard and handles fine, but when on plane in mild chop (and worse) the people and stuff inside get soaked with spray from the bow plowing through waves.


The boat weighs 2500 +/- a couple 100. Powered by a 4.3 Mercruiser with an Alpha 1 with a drive ratio of 1.83. I've attached a pict of the hull and we generally run with a full tank 35 gal and 4-5 people on board. Once on plane, trim has little effect other than to eventually ventilate the prop.


I've tried 14.5 x 19 3 blade, 14 x 20 and 14 x 18 4 blade, and 14.5 x 21 SS 3 blade. All got the motor to (or very near) WOT with described load.

I've owned many boat over the years and never had this problem before 0 I'm at a loss. My question is is it time to sell the boat or buy a different Prop? Any help would be great.

Thanks
Scott

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

Scott, 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 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, and especially all the information that is in RED as I have a program I designed to find the right prop for any planning hull boat that needs this 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.
That picture doesn't seem to represent an aluminum deck boat, is that the correct boat.

Iboats Boat and Motor Info

H

 

[scrkw2000]

Re: We get soaked on plane - Prop Problem??

Thanks hwsiii - I'll get as much of that info as I can and then repost. Yes, that's the correct boat. I took the picture in my driveway this morning.

-Scott

 

[jerryjerry05]

Re: We get soaked on plane - Prop Problem??

This might seem silly.When under load do you use the trim function to raise the bow?I helped a customer one time and they had no idea the drive was adjustable.J

 

[scrkw2000]

Re: We get soaked on plane - Prop Problem??

I use the trim all the time hoping that something miraculous will happen as I trim it up. But, alas we still get soaked. There's just no appreciable effect while on plane and eventually I ventilate the prop. Same situation for all the props I've tried.

I've been checking websites to gather the info that hwsiii asked for and found that Fisher no longer makes the boat. I think maybe what I have is a hull design flaw.

scott

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

Scott, can you just get me this information.
Model of boat with length and width.
There should be a tag in the back of the boat with the weight of the boat.
I need the HP for the motor and factory reommended RPM range.
Do you have trim tabs or a stingray type of device for the AV plate.
Exactly what make and model of SS prop did you use.
What make and model and sizes of aluminum props.
Degree of Vee in hull.
What speed and RPM did you get out of the SS.
Picture from the stern of the boat down low with the outdrive at the normal running position.

We need a high rake with tip cup prop to get that bow up, get me this information and I will recommend a prop that hopefully will do this.

H

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

Scott, I called Nathan at Tracker Marine, who now owns Fisher. I told him about the problems you were having and he is having Jeff call me tomorrow to see if he can help. He says they recommend a 14.25 x 21" aluminum prop for the mercruiser option on this boat, assuming it is the Freedom 2010 model which is 21'. In my mind we need a High Rake with added tip cup for the boat to raise the bow as high as possible.

H

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

Double Post

 

[scrkw2000]

Re: We get soaked on plane - Prop Problem??

Thanks H - Here's what I got so far.

Props Tried -
Laser - 14.? x 19 - Worst one all round. Ventilated on hard exceleration or slightest turn.
Stilletto - 14 x 21 - fastest of those i tried but still - couldn't get to WOT with only 2 on board.
Michigan Wheel 14 x 19 - don't know model - big blades - this is what was on the boat when purchased. Works ok but ventilate on turns. Get to low side of WOT with this one.
Mercury Marine - Alpha 4 14 x 20 - rpm too low - had the prop guy bend it to 18 pitch - get low side of WOT (4400) now - this prop is currently on boat.

here's a what I can find of the rest (i'll attach pictures to help).
1. Fisher Freedom 2010 aluminum deck boat - it's 20' 8" long
2. Beam is 8' (92" at waterline)
3. Its a 4.3 mercruiser (190 hp) 6 cyl, 2 bbl,
4. Alpha 1 outdrive with 1.81 ratio
5. We ski & tube mostly.
6. I don't know the base weight but the tag says max is 2100 motor, persons, & gear - and I'll bet we're right at that if not slightly over.
7. WOT is 4400-4600
8. No trim tabs.
9. I have no idea about the degree of V but I'll attach a picture or 2.
10. The top of the drive is just below the water stain on boat.

Thanks for your help
Scott

 

[APPALOOSA2]

Re: We get soaked on plane - Prop Problem??

I think its the hull design, looks pretty low with not much deadrise more like a flat bottom.

I would add a spray rail and be dry with all props !

 

[scrkw2000]

Re: We get soaked on plane - Prop Problem??

What's a spray rail???

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

Sorry I took so long Scott, I was working on another one and it was mainly the hydrafoil problem and high speed. I am sure you can guess that Jeff didn't call LOL. I did find the weight to be 2,700 pounds with the motor.
I ran my program and it shows you need a 19" Pitch prop for full RPM, right now it appears you are using a large blade surface area prop with the Alpha 4 prop. I haven't figured out the right prop yet, because by the way the Laser did for you it is obvious that you need more blade surface area than it has. A High 5 from Mercury in a 19" pitch might work as it has 24 degrees of rake for high bow lift and a lot of blade surface area, but they are expensive and I am not sure it will do the job and I don't want you to waste your money. Since I don't have any speed and RPM numbers I am not positive the 19" pitch would be correct. Let's wait until monday and I will call Jeff myself and see what he says. It definitely needs bow lift, I am just not sure anything can develop enough to raise the bow to where it needs to be. If it is a hull problem apaloosa is right about adding spray rails on the bow to deflect the water back down. I will call Jeff monday and not wait on him to call me back.
You can check the last 5 feet of the hull close to the transom and run a STEEL 36" ruler across the bottom of the hull pointing to the bow and stern and then move it sideways and look for a depression in the hull that would indicate a hook. A hook is a large concave area on the bottom of the hull near the stern, that acts like a trim tab and raises the transom and lowering the bow and increasing the wetted surface area and preventing the bow from rising with the correct high rake prop. You can also try a string starting at the stern going to the bow and see if there is any concavity in the stern area, it should be very obvious if it is, it doesn't take much to cause this.
Here are the numbers. And bu the way it is a modified vee hull not a deep vee.


Boat and Motor

Prop Picker

H

 

[hwsiii]

Re: We get soaked on plane - Prop Problem??

A spray rail is an appendage to the outside of the hull that deflects the water that would come over the bow or sides of the boat back down into the water instead of letting it rise over the bow or sides and creating spray. I will post a Picture for you and you will recognize it you probably just didn't know what it was called.

Sorry I was posting as you wrote the question. LOL


H

 

[APPALOOSA2]

Re: We get soaked on plane - Prop Problem??

90% of aluminum boats have them,hwsii is correct the water that goes up the side of the hull hits it and is directed back down.

 

[dingbat]

Re: We get soaked on plane - Prop Problem??

A "wet" boat is usally caused by a poor bad hull design. Here is a very good explaination of how the hull design makes for a wet or dry boat.

http://books.google.com/books?id=-3..._WnAQ&sa=X&oi=book_result&ct=result&resnum=10

 

[APPALOOSA2]

Re: We get soaked on plane - Prop Problem??

When it comes to aluminum hulls you won't find a deep vee. I don't know why but I ASSume it has to do with the shaping of aluminum on a smaller hull.
If you look at most non planning hulls they all hay spray rails, most wooden boats also had them.

I would see if a aluminum boat builder would sell you just the spray rails. That way you have aluminum on aluminum and you can pop rivet it on.

You will need to have the boat in calm water and level and mark the hull where it meets the water at the chine on the side, at the bow you will want it to flare up.

You can google a ton of pictures of Starcrafts or Crestliners and see where the spray rails are attached and how they work.

This is not a hard fix and you can find tons of help on the boat restoration pages here at Iboats.