Newbie

Hi all

Since I'm new at Engine driven craft I'd like som inputs on these thoughts
Facts

Got an 19 feets speedboad (Race type) with 24 degrees V hull originally suited for a Outboard in 150- 200Hp
Somewhere in history A geek ( no mee,This time) had the stern rebuilt and placed a 455 old engine with VP280 drive, and used this for couple of years.
I got hold of the boat as an payment for removing it from the seabed ,After a long Jump the boat had sinked ( No floating device at all) .
This was the history of wessel now to the present time:

Now i'd removed the transom, nearly al of the stern actually ( due to Alot of rotten wood) and was ready to rebuild it like stock ,WHEN
A Surface drive "Surfaced" for a resonable price ,Since I got a Ford 351W in the garage that suitable and a Powerglide that will fit , The old Idea of rebuilding to a OUTBoard boat Again faded away,Especially since I have to buy a new Outboard.
So Now to my Ques:
What should I think Of?
The engine wil give 390Hp at 5800RPM
the complete boat will not be over 2600LBS
Can I go With 1:1( = high gear ) on the PG
How much Prop should i Start with ?4 -5 -6 Blades

I 'm Thinking of making the boat 3 feet longer and saw a Notch in to the "original" boat to make a Step and a "Water ski" the last 5-6 feet of the boat

I Know there are a lot of knowledge here ,so Bring it on
Fair winds
Lars
Ps
Excuse my por English
SSDD
Finally I don't claim I'm insane,But..

 

Sounds like an interesting fun project, do you have any pics of the boat?
Did you buy a surface drive in the end?

 

Here is the drive ---
And boat it will live on ,as you se it has some "paintjob" to do, I'will add some extra feet and a "waterski" for +50 Mph handling

 

Hi SSDD,

Firstly..... if you're getting 390 hp out of a Ford 351, and intend to power that boat with it.... well, if it stays afloat, it'll get up and run like a scared cat.

At 6.7 lb/hp I would expect a top end of around 60 knots. With careful tuning you might be able to coax 75 knots out of it.

In other words, it would have the potential to outrun the car that tows it to the lake. That can get real scary, real fast. Invest in some top-quality, race grade safety gear for yourself and your crew.

If you're considering modifications that extensive, you're probably (no, almost certainly) better off to fix up the hull you have, sell it, and put the proceeds into buying a hull of the type you want. I'd suggest you either stick with fixing up the hull you have, or look for a different hull of the type you want. Such extensive modifications to an existing hull are likely going to be disappointing.

Sizing of surface drive propellers cannot be accomplished using the slip or Bp-delta methods used for submerged props. Pretty much the only way to accurately size them is to review the boat's design and key parameters with the prop supplier of choice, and they will help to identify which formulae are applicable to your particular case.

 

Thanks a lot for your input
Actually I just came back from the Dynorun of the "Sister" engine to mine and it pulled well over 440Hp at 6800Rpm the only thing that differs to my installation is the exhaust ,,This was with Car headers mine will be with normal watercoled manifolds ant a silencer made of 8 inch rubertubing filled with ol Go-cart tires ,
Anyway I'm useing an mild roller camshaft so there is room for improvment , the engine i set upp for E85 and it seem to work nice ,even at 12,5 :1 in compression
For being able to reverse I'm going to attach a Powerglide so i will have First gear at 1:76 and second to 1:1
This will be intressting to see, if ther is any gains here!
About the hull
For me, the Composite work is problem since I do rebuild Sailboats (trimarans) and use Epoxy especially with Vacuminjection , and gets good results
After consulting with local racers here ( they actually raced with these kind of hull allready 20 years ago , then with 90 hp outboards) they use to do the kind of rebuild i thougt, and race them with 200HP Merc with good results and as you said they reach 75-80 knots with fine tuned prop and the engine on a elevator bracket.

So I'l push on ( I mean I can always Retransplant the "power/drive"kit to a another hull)
This will be a good test rig and I'l learn a lot or...
Fair winds
LA

PS
I did tell , that the former ovner did have an old IRON old 455 with a vollvo280 sterndrive for serveral years ,, with good results..
Ds

 

Looks like a very good project, and it sounds like you know like you know what you are taking about.
Extending the hull and adding a planing pad, or ski is probably a good idea. What make is the hull? An old Frodee/Argo? Looks quite narrow.
How long is the power glide transmission?