big motor small boat......

[motard_mike]

gday guys, after days of searching the forums its time to ask the question....
i have a 14ft swiftcraft stilleto from the 80's or there abouts and a 140hp v4 johnson. now i know thats alot of motor for the boat but thats what i've got. any way i am getting a few cracks along the back edge of the outbord well where the top deck joins the transom. the transom is still solid and doesnt show any signs of rot so thats all good i just want to beef it up a bit. so here is the plan.....
22mm ply cut to the shape of the transom on the back of the outboard well and glassed in for the top mounts. then i will glass the top deck to the transom all the way around the back and make it water tight as im getting water in from over the transom but under the top deck this only occurs when people are geting in the boat. then i was thinking 6 mm alluminium plate about 600mm x 300mm for the bottom motor mounts on the inside and another alluminium plate on the outside between the motor and transom. i was thinking about 400mm x 600mm for that one again in 6mm thick. the idea was to spread the load as much as possible and tie the top deck into the transom. what do you think?

 

[F14CRAZY]

Re: big motor small boat......

I'm thinking that's simply too much motor...

 

[sschefer]

Re: big motor small boat......

I'll risk a little criticism. The point you need to strengthen is not the transom but the knee brace and the point where the transom meets the rail cap (assuming there is one). The rail cap actually takes the brunt of the stress and spreads it throughout the length of the boat on both sides.

I think if you beef up that connection you might lessen the problem. But, as was just stated, you're over powered. Either get a smaller motor or a bigger boat and live longer.

 

[motard_mike]

Re: big motor small boat......

yeah i take your point i just thought that spreading the load and tieing the top deck to the transom would be enough. adding another knee brace or beefing up the original is a little more work that i was trying to avoid. down grading the motor is not an option as the Johno i have now has a brand new power head installed at a cost of $6000 AUD by the last owner and i could never recover that cost selling the motor. it sits in the water very well and while it moves along very well it doesnt feel overpowered or unsafe.

 

[JaSla74]

Re: big motor small boat......

Looks fun, like a Mazda Miata with 350 small block stuffed in it.

 

[oops!]

Re: big motor small boat......

I'll risk a little criticism. The point you need to strengthen is not the transom but the knee brace and the point where the transom meets the rail cap (assuming there is one). The rail cap actually takes the brunt of the stress and spreads it throughout the length of the boat on both sides.

I think if you beef up that connection you might lessen the problem. But, as was just stated, you're over powered. Either get a smaller motor or a bigger boat and live longer.

nuthing wrong with this post sschefer.....you told him the right way how to do it then tryed to save his life by telling him hes crazzzzzzeeeeeee

 

[SuzukiChopper]

Re: big motor small boat......

Can you take me for a ride in that thing?! Looks like it'd be a blast!

Seriously though, if the last owner put the cash in to that motor, and assuming you absorbed a minimal amount of it when you bought the boat... I'd be looking to trade down that motor with someone who has an underpowered boat. I'd say either that or pull the cap and and start beefing up the structure to ward off the inevitable failures you're going to see. Not going to say that the motor can't stay but I will say that the factory most likely didn't build that boat for that size of motor. Would really hate to see a post from you in a year saying your transom got ripped off the back of your boat... or worse!

 

[oops!]

Re: big motor small boat......

actually......to be serious for a moment......you are way over powered. to beef up the boat is a lot of work.....but it can be done.
after re-reading your post......id really like to see the cracks you are talking about........they might be a lot more serious than you imagine.

to properly fix the boat to handle that kind of power.....tou will need to knee the transom to the hull and re tab it, but you will most likely looking at a total new transom.

if you search the hull ext thread, the index will take you to the appropreate pages........its not that tough to do .....but the top cap has to come off.

 

[SuzukiChopper]

Re: big motor small boat......

id really like to see the cracks you are talking about........they might be a lot more serious than you imagine.

This is key. The gelcoat on my boat, pretty much all of it, is crazed because the structure was so water logged and rotten that the boat flexed. A LOT! The first year I ran it I could feel the stupid thing flex. A crack is a sure fire sign of weakness.

Like oops! said, it's not like it can't be made better but it will take time and $$ to do it. There are plenty of people here that can make that boat safe with that motor. There really are only two options. Re-rig with a suitable motor or re-structure for that motor.

 

[motard_mike]

Re: big motor small boat......

thanks guys, its the middle of summer here (Australia) so im keen to get it back out on the water asap. to give you an idea of $$ situation i paid $1200 for the boat after it had been sitting in the yard unused for 12 months. so far the whole rig owes me about $3500. ill be pulling the motor off tonight after work with a mate and ill get some photos as i go. it has taken alot of abuse allready towing skiers, tubes and wake boarders with both 19p and 23p props and it has never done anything that worries me. any way ill get photos up and we can go from there.

thanks again.

 

[keepNitreel]

Re: big motor small boat......

thanks guys, its the middle of summer here (Australia) so im keen to get it back out on the water asap. to give you an idea of $$ situation i paid $1200 for the boat after it had been sitting in the yard unused for 12 months. so far the whole rig owes me about $3500. ill be pulling the motor off tonight after work with a mate and ill get some photos as i go. it has taken alot of abuse allready towing skiers, tubes and wake boarders with both 19p and 23p props and it has never done anything that worries me. any way ill get photos up and we can go from there.

thanks again.

Middle of summer Today here in Petersburg , Virginia was a little above 0. Personally I think the motor looks hanging on the back. BTW how fast have does she go without leaving the runway

 

[Bob_VT]

Re: big motor small boat......

To fix it the right way and even obtain more strength in the ski tower the cap has to come off. Consider what you have recently invested and if you want it to last do the repairs right.

Once the motor is off..... 2 people can have the top of the boat off in less than 1 hour.

 

[motard_mike]

Re: big motor small boat......

ok guys,

so several beers later and i got the motor off and had a good look in there. to my surprise teh side that i thought was cracked was actualy pretty good and the reason that it was uuder extra stress was that the other side of the deck was not attached to the transom at all..... i cut away the top deck where it was cracked to reveal a wet but not rotted transom.. i mean it was damp to touch but not wet or soft. any way ill keep digging tomorrow and see what i come up with... what do you guys think so far? am i looking at major work or can i salvage this.....

 

[motard_mike]

Re: big motor small boat......

 

[motard_mike]

Re: big motor small boat......

 

[motard_mike]

Re: big motor small boat......

sorry for all the photos but at least you can see where im up too....

 

[oops!]

Re: big motor small boat......

thanks for the detailed pics mike.....it really helps us help you.

ok......there was some de-lamination in the outer areas of the splashewll where the well joined the cap.....a major structural area. as well.....the transom it self is showing signs of delaminating. this is the first signs of imminent failure.
id say you pulled it off at exactally the right time.

so......what do you want to do.......patch it and go? or do you really want to fix it correctly. now it the time for that decision.

there is however one variable......the actual transom wood.....you will need to take core samples......drill into the transom with a 3/16 th bit......(wrap a peice of tape around the bit 3/4 of an inch from the tip of the bit as a stopping guide)......take a look at the wood shavings.....wet is not good.

(you will eventually need to fiberglass the transom in (to hold the big motor) and resin wont adhere to a moist surface).

here is a quick over view of the steps to fix it.

1. pull cap off
2. dry and treat or replace transom
3. fix and reinforce the cap by fiberglassing it.
4. add 2 extra "knees" (pic number 8)
5. tab and re wrap the interior of the transom.
6. reinforce the tower.
7. replace cap.
8. fair, finish sand and paint.

now......here is the snag.....if the transom is wet.....rot has started.....you will need to dry it totally.....then treat with git-rot. and re-dry.
you can just replace it with ext grade ply.....but even that comes wet from the store....so it will need to dry for at least a week with a fan and a heater blowing on it......if your area has high humididity....you will need to take the humdity out of the air while its drying.

if you can find some dry marine grade plywood from the local lumber yards....they will sell it to you with varying degrees of dryness....get as dry as you can.

there is a composite product called penski board that is avalable that you can use immeadately because its dry....a little more expencive...but it can save you a week drying time.

the job is approximately 75 man hours.....2 guys = 1 week and 7 x 24 beer.
a pro could do this job in under 30 hrs. the cost for you and your mate to do it is $250 (not including beer)

if you are unsure of how to knee the transom....or tab it....or for that fact even fiberglass it.......just search here.....read the hull extension in progress thread....it has detailed pictures and procedures of how to do what you are going to do.

if you are too lazy to do this or too drunk.....just p.m me and send me a plane ticket.......ill do it for ya !

cheers
oops

 

[motard_mike]

Re: big motor small boat......

ok guys time for todays update...
i was up at 8am today and on the tools. i have ground out all the gelcoat from the areas i want to put fresh glass and ground out all the cracked glass ready for the new stuff. i have also cut the ply to fit the back of the well and have acheived a nice fit there. during my lunch break i went to my lical fibreglass suplier and got the resen, matting and flo coat oh and most importantly some friendly advice.
i also cut an inspection port in the back floor as i wantted to have alook as i\the very back of the floor was soft. i found that all the ply has rotted of that section of teh floor... its only teh back corner and the rest of the floor has been replaced and is still very solid so im just going to clean out the wet ply and do up the cap...... i checked teh stringers and knee and they all look great.
pictures will be up again guys so let me know how you think im going.
im off to the beach for a quick cool down then i can get photos up and start glassing. oh yeah and beers soon too as all the work with power tools is done for the day.

and oops, it realy sounds like you know ypour stuff im just not convinced that the boat is worth the effort or if it really needs that much done... let me know what you think of the work today when i get it up

cheers and thanks again guys.

 

[motard_mike]

Re: big motor small boat......

 

[motard_mike]

Re: big motor small boat......