Old 1960's speedboat

I am converting a f/glass 13ft speedboat into a fishing/pleasure boat.I am replacing the transom completely.At this stage I am contemplating changing the transom height,at the moment it is 16".Does it make much difference to change the height of it so that it will take a standard or longshaft outboard?
I believe a 25hp engine is suitable,if I increase the hp,which will of course increase the weight,will it be stern heavy and ride too low in the water?
It is an open boat,and I am fitting new stringers and a grp deck,and possibly a lightweight cuddy.
I haven't owned a boat before,but have been out on boats owned by friends.
I intend using the boat off the N Wales and Lancashire coast.
I am a pensioner wth a somewhat limited budget,so any tips as to where to buy strand f/glass and resin etc would be greatly appreciated.
Concerning the safety aspect,what would be the minimum sized engine I would need to cope with tides wind and currents,for instance in the Dee estuary.
Any advice will be gratefully recieved.

 

A 13' boat isn't going to tolerate much additional weight, so the "light weight" cuddy should be reconsidered, unless it's a fabric dodger over bent tubing (which works well).

Yes, you can increase the transom cutout dimensions, to suit a long shaft and it's all I recommend any more, as the 5" difference isn't significant enough to screw anything up, but the benefits of a taller transom can be huge in a following sea.

Set your cutout so the ventilation plate on the outboard, is even (same depth) with a straight edge off the bottom of the boat. A little deeper is okay (an inch), but shallower is likely to cause issues.

As to UK suppliers, I'll let those more familiar with them chime in.

As to the engine you can use: what is the exact length, max beam, width of the transom and general shape of the boat? Can you post a picture or two. 25 HP should get you up and scooting along well enough.

 

old speedboat

Thanks for the helpful reply-PAR
I was a bit concerned about a following sea,and adding 5" onto the transom height sounds a great idea.
The boat is exactly 13'long,the beam is 5' at the widest point.The transom is exactly 4'wide at the top,widening to 4'-3"at the base stringer level.
The stringers go from the stern to 4' from the bow.The bow is covered by f/glass sheet for the first 4'.
The overall shape is a sleek looking bow,which becomes an almost flat hull after the first 5'-6".
The boat stood for a while when the last owner had it,and though it was covered,all the timbers,except for the in the hull stringers needs replacing,which I intend to do.
I think I may have to get assistance to post a picture,so if I dont succeed this time,I will post one later.
I will have to go back to the drawing board about the cuddy,I definately need some sort of cover,the rain here in the uk seems to prevail 50% of the time.

 

You could get away with a 30 HP on that boat, but considering the shape of her bottom, you shouldn't use more then a 25. Using some basic math, you should be able to get over 30 MPH lightly loaded with a 25 HP outboard.

The partially cover hull ('glass) is a concern, as moisture can get in underneath the fabric and start rot. Remove the bow piece or continue it aft, to include the whole of the exterior.

 

Hi Par,thanks for the reply,I think I may not have explained the bow f/glass section properly.The piece that is on may have originally been made of ply,it has timber arch braces underneath to support it,with cross section supports in between these,and I should imagine it could be walked upon when dropping the bow anchor.There is provision underneath it to fix the anchor roller.It covers the top of the bow for the first
4' and makes a storage area in the bow.I intend to replace all the timber structure on the boat,including the arch supports and gunwhales thro'out.I would like to bob along at 30mph,but I was considering a 15hp-20hp for ease of handling and economy,if the boat will plane and handle wind and currents safely I think it would be my choice.I have to trailer the boat about 80miles to the sea,and when it is parked on my drive the engine will need to be removed and stored inside for security reasons,
When I re-deck the boat I intend to put pack up stringers onto the originals to enable me to fix a flat deck,at the moment the stringers follow the curve of the hull.I suppose it will be a bit mind boggling equalising the heights,if I cant make the measurements with a laser,I suppose it will come down to straight edges and string.To get the deck shape I intend to measure equally from side to side in increments of 6"-9"from the stern to the bow,then f/glass it in,I suppose keeping the deck as low as possible would keep the centre of gravity down and give more depth inside the boat.There are no seats in it at the moment,but because it will probably have a tiller I thought of side bench seats at the back,and one either side under the shelter/cuddy at the front,this would allow more deck space for fishing and moving about.
I hope I am not boring you to death,it's just very handy to speak to a pro.

 

Most warped bottom 13' boats don't do well in the "sea". They are typically best suited in the protected waters of rivers, lakes and small bays.

Curved structural elements, such as the deck are much stronger and lighter then flat elements, which is one reason they are employed. Another reason is to shed water, which flat surfaces don't do very well. You'd be best advised not to make substantial changes to the design's structure. 13' boats can't tolerate much shifting in weights or the CG can move to an undesirable location. The same is true of additional weight. A 13' boat just doesn't have much capacity, unless it's unusually shaped (fat). Something as simple as adding a deck or "beefing" 'er up, can ruin the abilities of the boat (can't plane off or worse).

Post some pictures so we can see what you're trying to do.

 

Hi,I will have to wait until weekend to post some pics,my brother will put them on for me.My boat is in my back garden under a gazeebo,and the weather here in Manchester is foul at the moment.I have removed the transom completely,but left the gunwhales intact so that I can maintain the measurements and rigidity of the hull.This boat had no deck when I got it,just flimsy duckboards between the stringers,which rested upon the f/glass hull itself.I can scan in a drawing and send it at weekend.

 

Will watch for your pics.
Watching other people work on their boats helps when I have to work in the office to pay for my next

 

old speedboat

stanfred@live.co.uk

Cant figure out what my URL is which is required by Boat Design,I can email pics direct if you are ok with that.:?:

 

Stan, just use the "Manage Attachments" button in the "Advanced" portion of the reply section (not the Quick reply box). This button will let you upload images from your machine to this thread. It might be helpful if you looked over the FAQ section on this forum, which will cover uploading images.

 

Hi Par,I intend having a try at posting pics.
I have another query,is it possible to use constuction site expanding foam to fill in gaps around the edge of a new deck before f'glassing it in? I use this foam around window and door frames and it seems to "solid" everything in,and weathers well when painted.

 

boat pics

Hope these pics get posted:

 

Hi,the boat project is a bit more advanced than these pics,I have removed the transom completely,apart from the last 2" on each corner to enable me to maintain the shape and rigidity,there is no timber left in the transom.I have removed the stringers that are on top of the basic design stringers.I intend balancing the heights of the new ones to enable me to fit a flat deck.

 

Hi PAR,
not sure if you got these pics,pc's are not quite my Forte as of yet.

If you dont respond,I will post them on a new thread to make sure you get them.:

 

The pictures are fine Valvebounce. That hull is what we call a warped bottom. It's a classic style of this configuration and basically a nearly flat bottom hull form aft, with a "V" shaped entry. This set of shapes, is very well suited for protected waters use (lakes, calm rivers and bays) where they can scoot across flat water. The hull form is very efficient and gets up on plane fast, using little fuel in the process if not over powered. The bad thing about this type of hull is they don't do well in chop or steep seas. They also don't like beam seas either. They pound unmercifully in anything more then small waves and if over driven, they launch themselves off every other wave and crash back down with considerable force. In short, not a boat well suited for deep water work.

You'd be best advised to use a 20" shaft engine and seal up most (if not all) of the transom cutout, when you rebuild this area. A splash well is necessary too, especially if you insist on taking her into deep water. Most boats of this size, swamp with water coming over one of the transom corners, typically while someone is standing there doing something. A splash well can help in this regard, though will cut into the cockpit space a little.

The photos show a little distortion in the hull bottom. The trailer is probably pushing up and the broken/mushy stringers not holding the bottom straight like they use to. It's important you get the aft sections of the bottom right, or she'll do weird stuff on you underway.

A 20 - 25 HP long shaft outboard will push this little puppy just fine at the speeds you'd like. A 30 HP will drive her into the range where these hulls get "fidgety", though in glass smooth water, fast and fun, in slightly rough water scary.

That trailer is really the first thing you need to address. It's distorting the hull bottom which will make the boat run like crap. The bottom of your boat need to be dead straight in the last 1/2. If you put a straight edge on the bottom, parallel to the centerline, you'll see the distortions. Move the straight edge around, maintaining it's parallel relationship with the centerline, you'll find a hollow area, right where the trailer braces are. These need to be filled/fixed so the hull is again straight.

You can brace the hull bottom down (from inside) and hope the new stringers will maintain the new shape, but experience tells me the 'glass has retained this shape over time and you'll need to do some filing to fix it. With the hull "faired" back to what it needs to be, you can reinstall the stringers, sole and transom.