First resto project boat, question about foaming and draining.

Hello iboaters,

I've been reading up on a lot of great resto threads and appreciate all of the information that has been shared. It's a bit overwhelming at first to come in and try to soak it all up, but I'm working on it.

Anyhow so I purchased my first boat and it seemed like a good enough deal, 85 Four Winns 170 Candia deck boat. My wife wanted a pontoon and I wanted a ski boat, so this was an in-between that seemed to fit the bill. The interior needed work and the paint was faded and heavily oxidized, but no cracks in the hull and the motor is strong so I purchased it well knowing that all had to be done and probably more, boy was I right.

We took it out for a spin on Mothers day and had a blast and decided that we would get the interior done as the first step. After the upholstery guy started ripping into it I got a call and he said he pulled up the carpet and that I should come in and take a look. Well under the port side console the deck was really soft, actually pushed a screwdriver right through it without any force. I told him to go ahead and chop the floor and maybe we could repair it. Needless to say I was back in the shop the next day and he said the foam was saturated and he found some more spots. I had already read up on replacing a deck on iboats and decided to take it home and do it myself. After pulling out most of the foam I see now that the stringers are rotten in spots, not all the way down to the hull, but it will probably require me to tear out the old and replace with new wood and glass, then add some urethane pour in flotation foam for stiffness. The thing that I thought was a bit odd is that there are some cross braces over the stringers instead of full bulkheads, not sure if this is normal and if it is should I just rebuild it that way or would it be better to extend it to the hull? Also I noticed at the base and other areas of the stringers the fiberglass is bulging out. Looks like it might be bad workmanship from the factory (see in the pics), but I guess it could just as well be that the wood had adsorbed water and swelled the glass?

Is it safe to do a deck replacement without removing the cap and leaving it on the trailer? I'm tight on space and don't have the equipment to pull it off of the trailer and create a cradle for it. I was thinking to replace stringers one at a time and to brace it by putting some boards across the cap and bolting them in where the cleats would be. This could give it more rigidity during the rebuilding.

Now the original expanding foam had no way to drain to the stern of the boat which is what may have lead to the wood rott. They just poured it between the stringers and from bow to stern no drainage. How do other people address the lack of draining to the bilge area? My thought was to put in a 1 to 2 inch pvc pipe that's coated with some type of release agent and then pour the foam in little sections and pull the pipe from each chamber as it hardens. I welcome any suggestions and experiences others have had luck with or even failure (what not to do). Also after reading other posts about foaming, I think that the foam in this boat was structural so I don't think that the pink or blue rigid foam would be a good substitute. I'm new to all of this so I could be wrong and it maybe a perfectly acceptable substitute for pour in.

Here are some pics, they make me cringe when I look at them.







Thank you for any feedback or assistance.

Happy boating all!

Re: First resto project boat, question about foaming and draining.

Oh yeah and there are these hollow boxes on each side of the hull just above the deck. The only thing that I can figure is that they are there to add rigidity. Any thoughts?

Re: First resto project boat, question about foaming and draining.

The bulges on the stringers look like poor/sloppy glassing.

Utilizing bulkheads instead of cross braces will be a stronger build.

You're right on the expanding foam instead of the sheet foam, sheet foam won't fill and support your deck and hull like the expanding will.

There's a couple principals on drainage:

1. Some boats are designed with a deck drain system instead of a bilge drain, this drains all of the water that gets into the boat off the deck before it can make it to the bilge. This design will have a solid foam filled bilge with no bilge drain plug, the plug will be the deck drain plug that should be pulled when the boat is out of the water and not in use to keep water from pooling in the boat and finding a way into the bilge.

2. An active draining bilge will have a drainway down the keel the length of the boat and a bilge plug that will empty the bilge when pulled. It will also have a through deck drain, usually a hole cut through the decking toward the aft of the boat with a grated cover. This will let any water that gets on deck drin into the bilge and either be pumped out by the bilge pump or drain when the bilge plug is pulled.

The folly of many boat owners and main cause of saturated foam is due to the owners not removing the deck or bilge plugs when the boat is out of the water and bieng stored uncovered and exposed to the elements. The deck or bilge fills with water and over an extended period of time of constant exposure the foam saturates.

Keeping your boat covered with the plug out when not in use will eliminate 99.99% of waterlogging and rot problems.

As for your boat, you didn't say which system you have... bilge or deck drain, but since you're doing a full resto you can build it either way.

If you decide to go with a bilge drain there are some creative way you can form the foam to ensure positive drainage to keep your bilge dry when the plug is pulled or if you have an automatic bilge pump.

If you choose the deck drain system all you have to do is ensure that the bilge is filled solid with foam and with no voids for water to accumulate in. You'll also need to make sure your deck is properly glassed in and seal completely with no penetrations through the decking of protective fiberglass barrier.

Think about it and let us know which system you would prefer and we'll be glad to help.

Re: First resto project boat, question about foaming and draining.

Welcome to iboats . . .

About that glassing . . . it looks like "chopper guns" instead of chopped strand mat (CSM) or woven roving (WR). You can rebuild it better than new.

If you have not checked the transom for rot, now would be the time.

The pictures are great, looking forward to see the progress on this restoration.

Re: First resto project boat, question about foaming and draining.

Good morning everyone,

jigngrub said:

The bulges on the stringers look like poor/sloppy glassing.

Utilizing bulkheads instead of cross braces will be a stronger build.

As for your boat, you didn't say which system you have... bilge or deck drain, but since you're doing a full resto you can build it either way.

Click to expand...

Hello jigngrub and thank you for the info. Yeah I was thinking that it was a bad glass job, but I did not want to assume so. The tell tale signs for me was that foam was trapped under the glass there, like it made it's way under there when they poured the foam at the factory.

I think adding full deck to floor bulkheads between the stringers is going to be the way I go. Not that it was a horrible ride in the state it was in, but I like the idea of building something better than it was originally. I guess that's the machinist and craftsman in me.

Ahh yeah I didn't say which drain system it was, I wasn't even aware of the deck drain system. I've learned something new today, and I appreciate the info. I'm still new to boating, but everyone probably could tell including the guy that sold me the boat. I keep telling myself I bought a strong motor ha ha ha. Anyhow it has a bilge pump below the motor. There is no deck below the motor so the water can flow from the deck into the bilge cavity and out through the bilge pump or when docked through the drain plug in the bottom of the transom.

Since the boat was lacking a factory drainage channel or system below the foam is there a way to do this? For example using a perforated pipe wouldn't work because the expanding foam would penetrate this and block the perforation holes. My thought was to make some type of channel between the hull and foam that wold allow any water to drain down the foam into the channel and to the bilge area. After thinking about that though and reading what you said about sealing the deck up to the hull, I guess that wouldn't be needed?

My concern is the seat pedestals and other bench seats being bolted back into the deck and that becoming a place where water would penetrate the deck and get into the foam again and start the process over, unless there is a drainage channel below the foam leading to the bilge area. If anyone wants to comment or add some helpful advice I'm open to suggestions.

tpenfield said:

Welcome to iboats . . .

About that glassing . . . it looks like "chopper guns" instead of chopped strand mat (CSM) or woven roving (WR). You can rebuild it better than new.

If you have not checked the transom for rot, now would be the time.

The pictures are great, looking forward to see the progress on this restoration.

Click to expand...

Thank you for the welcome tpenfield. Yeah chopper gun, I saw a reference to that somewhere else and you confirmed it. Adding more glass over it is definitely in the immediate plans. I was reading on a few rebuilds and woodonglass has a great layup posted that I will be referencing as well as many other iboat members.

I did check the transom initially, but I will take a few core samples later. It actually looks in good shape and no sign of rott on the high end around the motor and outdrive, but I won't know until I pull the motor and pull up the last of the deck and see where the stringers and transom meet up. It could be rotted at the bottom, but I'm hopeful it is not because most of my stringers are dry toward the bottom half where they meet the hull. They are only messed up on the upper 1/4 to 1/2 of the stringer and the odd one where there was a hole in the deck for a table to be inserted. That area was destroyed by rot. The metal housing where the pole for the table would fit was deteriorated and it was wood below that. I don't think that the previous owner(s) kept it covered or inside so rain would get in quickly. Heck when I picked it up there was standing water in that hole for the table and if I had known then what I know now about standing water and wood and what that was, I would not have bought the boat.


Instead of using marine ply, what does everyone think about the Nida-Core H8PP boards? Looks like a lighter substitute for marine ply that would be a lot more rott resistant and add some dampening.

Thanks for the replies friends, hope y'all are having a great day. Post more pics of the bilge area in a while.

Re: First resto project boat, question about foaming and draining.

After reading again what I posted just now it seems more like the water that caused the damage was seeping in from the top of the deck because the wood at the bottom of the stringers was ok when I drilled into them. The only thing is that when I pulled the foam it was wet in a lot of areas down to the hull. Man that stuff never dries out. Anyhow so the glass work at the bottom of the stingers and hull wasn't compromised and they hadn't rotted there. Hmm... will have to re-think the idea of adding drain channels through the foam as it may not be needed. Just sealing the deck properly and making sure that any holes drilled in for seats or motor mounts are properly sealed.

Re: First resto project boat, question about foaming and draining.

Here are some of the pics around the motor showing the bilge area. I think that I would just use this system instead of changing it up jigngrub.





below the motor there is a bilge pump, the image didn't turn out so great, but I think everyone gets the idea.

Re: First resto project boat, question about foaming and draining.

I also noticed after taking some of the foam out that there was a thin skin left behind, not sure if it's fiberglass or from the foam. Is this anything to be concerned about? It's not all over, just in some spots.

Re: First resto project boat, question about foaming and draining.

It's from the foam. Remove it and clean the hull as clean as you can get it.

Re: First resto project boat, question about foaming and draining.

Thank you Woodonglass. I'll be cleaning it as best as I can, I've read up on your threads and there is a lot of helpful info there. Thank you for sharing. Is that white coloration of the chopper gun type of glass normal?

Re: First resto project boat, question about foaming and draining.

Hello iboaters,

Okay after searching and searching, sometimes it's the key words you use to search that help and sometimes just dumb luck stumbling onto another thread and finding what you were looking for without looking, I've found answers to my original questions about drain channel and doing a resto with cap on.

My idea was to run the drain channel between the hull and the foam to the bilge, but I didn't know how. After reading another post I could do something similar by adding foam by the false deck method and then cutting a channel in the foam and sealing it with epoxy paint from the top. This would give a clear cut path for the water to travel if it were trapped between the deck. A 1/2 by 1/2 channel was suggested, but I may increase that to 1/2 by 1 deep instead to clear the stringer supports.

If anyone has any other thoughts (pros or cons) I'm open to hear them.

I also read that it's common to leave the cap on in a stern drive deck and potentially transom restore. This was explained because the transom doesn't traverse the entire beam of the boat. Can someone step in and confirm this, it would be the best news that I have heard so far other than not finding rot in my transom when I take the motor out.

I purchased a cherry picker the other day and I'm going to try to remove the outdrive and the engine by this weekend so I can tear the rest of the deck out and inspect the transom for rot. Cross my fingers that I'm lucky and there is none.

Back to reading...

Re: First resto project boat, question about foaming and draining.

Pouring the foam with the false deck method and cutting out a drainway will work, or you could simply blockout a drainway before you pour the foam. This way you won't have to cut and remove the foam from the drainway and you won't waste the foam you'd have to cut out. It's a lot like pouring concrete (what I do) except the material isn't nearly as heavy.

Re: First resto project boat, question about foaming and draining.

You can leave the entire middle channel void of foam if so desired to allow for drainage. You are totally correct in that for I/O boats the Cap is NOT normally removed.

Re: First resto project boat, question about foaming and draining.

Jigngrub and I discussed grooving the foam as you mention in my rebuild thread. I decided against it because for one thing, it added several more steps, and for another, I like that the foam exerts pressure on the hull and deck when you pour it under the already installed deck to stiffen everything up. That was why I decided not to, but I still do think it is an excellent idea and if ever I do it again I might give it a go.

If time is not an issue it sure would be less aggravating during certain parts of the build to remove the cap. I don't regret leaving mine on, but sometimes it would have been nice for it to be off. Not to mention that I've got a few resin fingerprints on it that may not clean off.

Re: First resto project boat, question about foaming and draining.

Thanks for the replies everyone.

or you could simply blockout a drainway before you pour the foam.

Click to expand...

Okay jigngrub, I'm open to this idea, how would I go about blocking it out? Is there a way to remove the blocking material or should I use something like rigid foam and just pour foam over it?

You can leave the entire middle channel void of foam if so desired to allow for drainage.

Click to expand...

I would consider this too woodonglass, the only thing that concerns me is that there is a stringer in the middle so I would be removing about 1/2 of the flotation foam out of it.

You are totally correct in that for I/O boats the Cap is NOT normally removed.

Click to expand...

I think it was something you said in another post I read.

I like that the foam exerts pressure on the hull and deck when you pour it under the already installed deck to stiffen everything up.

Click to expand...

Good point mwe and I don't necessarily want to add more steps at this point.

If time is not an issue it sure would be less aggravating during certain parts of the build to remove the cap.

Click to expand...

Ahh I'm sort of in the same boat, so to speak, as you with your build. The family wants it back in the water now. We've only used it one time before I discovered all of this fun.


I have a lot to consider and more to read, thank you for the helpful information everyone.

G'night.

Re: First resto project boat, question about foaming and draining.

psykosteel said:

Thanks for the replies everyone.

Okay jigngrub, I'm open to this idea, how would I go about blocking it out? Is there a way to remove the blocking material or should I use something like rigid foam and just pour foam over it?... There's a few ways to do this.

The rigid foam is an option, but it would be harder to hold in place when pouring the expanding foam and may not be as durable.

Building a form that would be removed after the foam has been poured would be my option. You could use a cheap material like $13 a sheet OSB and it would be economical.

Another option would be to f'glass in a permanant structure to pour the foam against. It would be like an extra couple of stringers that would block out for the drainway.



I would consider this too woodonglass, the only thing that concerns me is that there is a stringer in the middle so I would be removing about 1/2 of the flotation foam out of it.... I would want the maximum amount of foam I could get in my boat while still providing positive drainage






Good point mwe and I don't necessarily want to add more steps at this point.... adding a step can have it's rewards in quality and durability.



Ahh I'm sort of in the same boat, so to speak, as you with your build. The family wants it back in the water now. We've only used it one time before I discovered all of this fun.


I have a lot to consider and more to read, thank you for the helpful information everyone.

G'night.

Click to expand...

The thing that really puts me off about pouring the foam after the decking has been installed is that installing foam like this isn't exact and after the foam has been poured you don't really know how good of a job you've gotten and you sure can't see it.

Pouring foam "blind" leaves/creates voids in the foam that can/will trap and retain water should intrusion occur and there's no way to drain these voids. The water just sits there until it eventually saturates the foam.

Take this tinny for an example:

Maybe this is an especially crappy foam job but it illustrates what I'm talking about.

We see these voids in all through deck foam installations, both fiberglass and aluminum.

When you use the false deck method of pouring foam you get to see what kind of job you did after removing the decking and any voids can be patched/filled for a complete and solid installation that won't trap and retain water.

Re: First resto project boat, question about foaming and draining.

Hi psykosteel welcome to the dry dock! Check out my Four Winns rebuild in my signature......you might get some tips on doing yours

Re: First resto project boat, question about foaming and draining.

Hi and welcome to the dry dock, "psykosteel"...
Here is a link to foaming using a "False/Mock Deck" method...http://forums.iboats.com/boat-resto...sion-progress-pics-234392-15.html#post3205843
It is quite involved, but will achieve the ultimate results...
Have Fun!
GT1M

Re: First resto project boat, question about foaming and draining.

jigngrub said:

The thing that really puts me off about pouring the foam after the decking has been installed is that installing foam like this isn't exact and after the foam has been poured you don't really know how good of a job you've gotten and you sure can't see it.

Pouring foam "blind" leaves/creates voids in the foam that can/will trap and retain water should intrusion occur and there's no way to drain these voids. The water just sits there until it eventually saturates the foam.

Take this tinny for an example:

Maybe this is an especially crappy foam job but it illustrates what I'm talking about.

We see these voids in all through deck foam installations, both fiberglass and aluminum.

When you use the false deck method of pouring foam you get to see what kind of job you did after removing the decking and any voids can be patched/filled for a complete and solid installation that won't trap and retain water.

Click to expand...

This is definitely true. The first time I removed the deck of a boat there were voids underneath the plywood with little tiny puddles in them. Granted that deck had been rotted all the way through for some time. I guess there is a trade off whichever way you do it.

Re: First resto project boat, question about foaming and draining.

rickryder said:

Hi psykosteel welcome to the dry dock! Check out my Four Winns rebuild in my signature......you might get some tips on doing yours

Click to expand...

Yep, RR did his Glass Boat with Sheet foam and did one of the best job's I've seen here on the forum. Packed every Nook and Cranny with the stuff, On Edge, and at a height that would support his deck just like the Poured in Foam. Excellent job, (RR, Don't go gettin the BIG HEAD now!!!)