1972 Cobia 15 ft restore

[madman960]

Already gutted. Forgot to take before pictures. Have not started removing floor or stringers or transom. Will take pics before going further. I will remove the floors and take samples of the stringers this weekend, weather permitting. I am certai the motor is to large for the boat, so I plan to sell the motor and get a proper size. The trim tag says it is rated for 70 hp and it came with a 135 hp. Not sure of SC law about over powering.

Bill

 

[GT1000000]

Re: 1972 Cobia 15 ft restore

Welcome to the drydock, madman960...

Check your PM {private message} box...

Make sure you not only take pictures, but take lots of notes and measurements...

Best Regards,
GT1M

 

[madman960]

Re: 1972 Cobia 15 ft restore



Finally got around to taking pictures. Did not get many. Started to rain. Still need to pull floor and sample stringers and transom.

Bill

 

[madman960]

Re: 1972 Cobia 15 ft restore

Hi all. Sorry it has been so long. We finally got back to short days at work and I also had spine surgery.

I pulled the center piece of the floor out today. Looks like PO replaced the 2x4s between the stringers. Looks like he did a good job of not ruining the fiberglass. He did not reglass the 2x4s down. He put screws into the old fiberglass matting. I will get pictures tomorrow.

I did find a plug in the bilge area when I cleaned the debris out. When I pick up the plywood to repair the floor, how much resin should I put on the bottom side? How long should it cure before I screw it down? It is about 32 in wide by 84 in long.

I still have the 135 hp Mercury. It needs a stator. I had it up for $200 but did not get any replies. If I were to replace the stator, would the 15 foot tri hull be able to handle it without any transom upgrades? I would not go full throttle. Trim tag says it is rated for 70 hp.

I live a mile from the boat launch so I can hardly wait to get it water ready. How do I choose a bilge pump? There is 1 installed but there is not a gph or other size rating on it. It does run if I wire it to the battery but it appears to be in bad shape. I really would not know as this is my first boat. I will be running all new switches and wires while it is torn apart.

Thank you for any help or thoughts on this project.

Bill

 

[jbcurt00]

Re: 1972 Cobia 15 ft restore

Lets break this down so it's easier to read, follow & answer:

I pulled the center piece of the floor out today. Looks like PO replaced the 2x4s between the stringers. Looks like he did a good job of not ruining the fiberglass. He did not reglass the 2x4s down. He put screws into the old fiberglass matting. I will get pictures tomorrow. I did find a plug in the bilge area when I cleaned the debris out.

W/out pix, it will only be speculation, but I'll give it a shot:
You removed 1 piece of the DECK (floor) plywood, that ran from gunwale to gunwale (boat sides) across the beam (width) of the boat, probably from about the helm (steering wheel/console) back towards the transom, roughly as it looks cut in this pix:

When I pick up the plywood to repair the floor, how much resin should I put on the bottom side? How long should it cure before I screw it down? It is about 32 in wide by 84 in long.

You should mix as much polyester resin as is necessary to coat the plywood once, allow it to tack off, and mix another slightly larger amount & reapply resin to the tacky surface of the coated plywood, and fully wet out a layer of CSM. Polyester resin w/ out the CSM is very brittle, and offers little substanative value against water & no strength.

This is a free downloadable, that gives rough estimates of poly resin usage w/ CSM & 1708

I still have the 135 hp Mercury. It needs a stator. I had it up for $200 but did not get any replies. If I were to replace the stator, would the 15 foot tri hull be able to handle it without any transom upgrades? I would not go full throttle. Trim tag says it is rated for 70 hp.

If you are asking if a 15' boat rated for a 70hp max is capable of handling a 135hp Merc, I think there is little left for me to suggest as a course of action, as it would seem your choice of user name is more then accurate.

Do you know what that Merc weighs, or the amount of thrust it's capable of, let alone what the gross overpower, by nearly 2X the rated hp, that motor provides? When it goes sideways, you can't just pull over & let the people unfortunate enough to be aboard, off at the nearest curb.

How do I choose a bilge pump? There is 1 installed but there is not a gph or other size rating on it. It does run if I wire it to the battery but it appears to be in bad shape. I really would not know as this is my first boat.

Try here for bilge pump info

 

[madman960]

Re: 1972 Cobia 15 ft restore

 

[madman960]

Re: 1972 Cobia 15 ft restore

 

[madman960]

Re: 1972 Cobia 15 ft restore

 

[jigngrub]

Re: 1972 Cobia 15 ft restore

You are going to rip out those stringers and put everything back right... aren't you?

 

[madman960]

Re: 1972 Cobia 15 ft restore

JB, you are correct. I pulled the piece that looked cut out. PO put it down and put carpet over it. Did a real hack job on the stringers too. Poly resin here at the local boat shop is $38 gal. Not sure if that is good. 50"x3 yards 1.5 oz matt is $33.

I figured the motor was to big for the boat but people around here said it would be fine. Lol.

Thank you for the insight.

Jig,

I plan to do my best at doing it the right way. There are some short pieces of 2x4 that create gaps in the stringer. I suppose that is incorrect. Or do those gaps act as baffles? ( like a muffler) Would I be wrong to use full length boards? If the gaps are intended to be baffles and I were to use full length boards; could I just cut mouse holes into the lower half of the boards?

Thanks for stopping by.

Bill

 

[jigngrub]

Re: 1972 Cobia 15 ft restore

Yes, the gaps in the stringers are incorrect.

Here's a good trihull restoration you can look at to get some idea of how your boat should go back together:

http://forums.iboats.com/boat-restoration-building-hull-repair/my-project-74-ebbtide-584261.html

 

[madman960]

Re: 1972 Cobia 15 ft restore

Thanks for the link. It was a great read.

Bill

 

[madman960]

Re: 1972 Cobia 15 ft restore

I am looking at taking the cap off and replacing the transom while I am replacing the deck and stringers. Are there any upgrades to the transom deck or stringers that would handle the 135 HP motor? If not, I will keep searching for a smaller motor. I figure the resto will take to at least July or August. I really won't need a motor until then.

Thanks;

Bill

 

[jbcurt00]

Re: 1972 Cobia 15 ft restore

I am looking at taking the cap off and replacing the transom while I am replacing the deck and stringers. Are there any upgrades to the transom deck or stringers that would handle the 135 HP motor? If not, I will keep searching for a smaller motor. I figure the resto will take to at least July or August. I really won't need a motor until then. Thanks; Bill

I stand by my earlier comments:

If you are asking if a 15' boat rated for a 70hp max is capable of handling a 135hp Merc, I think there is little left for me to suggest as a course of action, as it would seem your choice of user name is more then accurate.

Do you know what that Merc weighs, or the amount of thrust it's capable of, let alone what the gross overpower, by nearly 2X the rated hp, that motor provides? When it goes sideways, you can't just pull over & let the people unfortunate enough to be aboard, off at the nearest curb.

Bluntly: NO.........

Maybe this will help

From the 1st result found above, when I did a search:
5. Maximum Loading and Horsepower
The State of South Carolina does not have any maximum loading and horsepower
requirements that are in addition to federal regulations. To review federal regulations, refer to
the section on Capacity Plates included in Chapter 1 of this course.
The following information was approved by NASBLA and is included in Chapter 1 of the
Boater101 Course:
Capacity Plates
It is required for all mono-hull boats under 20 feet built on or after November 1, 1972 to have
a capacity plate approved by the USCG. In addition some manufacturers voluntarily install
capacity plates on boats larger than 20 feet. This plate must be visible from the operator’s
station. The capacity plate lists a safe motor size, the maximum number of persons to be
carried onboard, and the total weight the boat can carry including persons, motor, and gear.
When operating your boat be sure to adhere to the restrictions listed on the capacity plate.
Not only is it dangerous to overpower or overload a small boat, since they can swamp or
capsize more easily, but it is also illegal. In many states, there are fines and penalties for
exceeding capacity recommendations, including carrying more than the maximum number of
people.
On boats with no capacity information label, use the following formula to determine the
number of persons your vessel can safely carry in good weather conditions:
PERSONS (average 150 lbs. each) = Length (ft) x width (ft) divided by 15


Does that offer you an answer you will accept beyond my previous replies of NO ?

If you are interested in how or why the USCG makes those capacity plate ratings, you might try a google or iboats search for that, but a rough estimate can be determined by:
(Length in feet X width of beam in feet X 2)-90 round up to nearest 5 hp

So if your boat is 15' long, and has a beam of 7.5' (which is grossly overstated) you 'could' in theory run a 135hp motor, if the transom is built for a long shaft (20") motor. If it's a 15" transom, as is likely in a 1972 70hp rated boat, it should be a smaller motor on our theoretical 15' X 7.5' beam boat........

 

[jigngrub]

Re: 1972 Cobia 15 ft restore

Whut he said^^^^^

Sell the 135 this spring, but look for another motor now.


Overpowering a boat is a lot like drinking and driving, if nothing ever happens you can get away with it... but if an accident does happen, and it's not even your fault you will still be held liable. It's just not worth it.

Overpowering a boat will also void your insurance, and should anything happen you're on your own.

 

[madman960]

Re: 1972 Cobia 15 ft restore

Jbcurt00;

In my original post I asked " If I were to replace the stator, would the 15 foot tri hull be able to handle it without any transom upgrades? " I was pretty sure it would not. However; boaters around here said it would handle it just fine. That is why I asked on here. I read the SC overpowering laws when I first purchased the boat.

I asked if it would handle it with upgrades to structural supports. Cars are not made to handle 800+ HP but will with appropriate upgrades to the suspension frame and other areas. I figured I was rebuilding the boat so it would be worth asking if it would handle it with proper rebuilding. A simple no would have sufficed. I already said " If not, I will keep searching for a smaller motor. I figure the resto will take to at least July or August. I really won't need a motor until then."

Thank you for your advice.

Jigngrub;

The motor was on the boat when I got it. I have had it up for sale for awhile now. I will either part it out or put it in the shed.

Thanks.

Bill

 

[madman960]

Re: 1972 Cobia 15 ft restore

I did some work on taking out the stringers today. The center stringers rear portion will come out in 1 piece once I take the cap off. Tomorrow I will try to remove the 135 and the steering cable. Then I will start figuring out how to remove the cap. Here are some pics.

 

[madman960]

Re: 1972 Cobia 15 ft restore

 

[Woodonglass]

Re: 1972 Cobia 15 ft restore

To remove the cap you will need to remove the rubber insert from the Rub Rail and drill out the Hundreds of rivets holding it in place

 

[madman960]

Re: 1972 Cobia 15 ft restore

Woodonglass;

Sounds like I will be having a blast the nest few days.

Thanks;

Bill