Over weight boat?

John,

You see where I got the 17mph. Where does the 22 mph come from? You have to have a theoretical speed before you can enter the rest of the numbers, right?

 

Bruce,
If you look at my last post, 22 is the theoretical speed. 16 (mph)should be the actual with proper constant. (might be getting knots and mph mixed up)

Also, as stated in my figures, I show a max speed of 13.8 knots (abt 16mph), probably 12 K cruise. Your first post indicated a cruise of 9 knots (not sure if this is with a fouled bottom). 3 knots improvement is 33%. And yes it could be more especially if weight is less and/or power is greater.

 

John,

The 9 knots was cruise 12.4 knots it what the owner says they got yesterday at 2850 RPM. Any improvement would be welcome and the knowledge gained in these discussions is very much appreciated. I plan on visiting this forum regularly. I enjoy all things that have to do with boating and want to learn all I can.

 

Bruce,

You are correct. The max is only 1.4 knots improvement. I missed that. I suspect the calculations may be conservative based on other owners expierences, but figures don't lie, and I believe the Prop recomendations are correct. It's possible, the diesel manf. ratings are consevative, which could allow for slight pitch increases and more speed.

 

John,

I thought I was getting done with my posting on this boat and topic but I just received some interesting data from the owner and broker. I'm attaching the info and would like your feedback. I'm adding more pictures on the next post.

 

More pictures. From the looks of the prop area it doesn't look like a person would be able to get a 28" prop. With the 32" area what would be the max you could get?

 

Bruce,
Since your prop is only turning a max of 1160 rpm, clearances can be minimal. In Lieu of the 28 x 20, My software Shows a 26 x 21, 4 Blade .66 D.A.R. Min. Slip should be down to 32% with max speed of 16.6 mph or 14.4 knots. Only slightly more than 13.8 K, previously provided, but more efficient than the present set - up.
2 knots (16%) better than current. I don't really see any more improvement posible.

 

Bruce, It looks like there is at least some slim build up on the bottom. A cleaning could get you a couple miles an hour gain. If that has been in the water for some time I would call that condition normal. If it were a year its probably got a high end bottom paint on it. My brother in law went from a small wheel 2 to 1 to at 28 x26 behind a 2.5 to 1and had a big speed improvement. His is presently the fastest BHM in the harbor. He just put a 26 X 28 wheel on it this june and it made no difference in speed from the 28 x 26.

 

Bruce. Was all that stuff on it when they did the speed run? It looks like there is a hard bottom inflatable on the overhead. The Anchor is up on the bow. I realize the stainless rails are perminatly affixed but I'd lose that weight too. I bet there is a ton of stuff that could be taken off that boat easy. Even moving the anchor off the bow could get you a 1/2 mph. Stick that kind of stuff aft as much as you can.

 

hemidodge,

How much clearance does your bro in law have for his prop? As you can see from the pictures I posted there is a 32 inch clearance on this boat. Does he have more than this?

John says the prop clearance should be 10%. So the clearance is the 32 inches minus the 3.2 from the top and bottom which leaves 25.6. I believe this is why John is now recommending a 26x21. Is this correct John?

 

Hemidodge,

Some of the stuff could be taken off but do you think this would really make much of a difference? One of the things I like about the boat is the railings. The hard bottom dingy could be changed to a less weight type but I like the the dingy feature. We do a lot of beach landings because the lack of docks so in our area some sort of dingy is important.

 

They are all the same hull so you can assume and be safe in doing so that the space between is 32 " also on bro inlaws boat. His boat hull was built extra heavy also. His boat sits higher though. After seeing the photo i think your speed might be at a factor do to weight mostly. I guess I should point out that if you are turning the 24X 24 correctly You should also swing a 26 x 22 easyer and you might turn the full 2900 rpm.

 

Bruce Do you have a link or adress to the 3208 spec sheet? tia

 

Hemidodge,

Here is the spec sheet.

 

Yo Bruce...Not to stick a thorn at you but.... Ya think the engine is getting a little old? I'm don't recall any mention of hours on it but even if it is very low. I would be concerned how long you will have before major work or a repower souly on its age.