Building a '93 Caravelle 1750 Classic Bowrider

[Reserector_]

I found this to be a good read. Nice Deck!
https://www.yachtsurvey.com/fueltank.htm

That is the main article I went by. It was the clearest and most concise write-up I found.

I realize that this is a tired old topic, but as I read thread after thread of different boaters' drivel, I found that there were more mounting methods and opinions than there were types of tanks and places to put them. I had to call BS on much of it and start looking at manufacturers sites to see what they recommend. That's how I found the ABSC standard.

I think it's good to challenge opinions and workmanship. So know that I appreciate it. I was just about to accuse you guys of going too soft on me. LOL The main reason I joined this forum and started a build thread was to create accountability for my work with a group that could catch a blunder before it escalates.

I think I have it well supported to allow expansion. The plastic can flex if it needs to. I chose the support location because although they rest on the bottom, they are at the toe of the stringer tabbing, a few inches from the stringer. Should be plenty stiff there. The original tank was plastic and rested on two pieces of rub rail insert attached to the bottom center wood with one screw each. No other attachment. Just dropped in the hole and glassed in. It survived fine until it sat in the sun for 15 years. It might still be usable, but I wouldn't trust it.

Anywho, what I have now is more supportive than stock.

Factory tank and a view of the vinyl supports...

 

[kcassells]

You are just lucky! Lots of the tough guys are in hibernation. Udders are whimpy about this subject. They just hide and read.
Ahhhhhhhhhhh… see ya in a few mos.
Lookin good!

 

[kcassells]

I would still put a pc. of glass ply under it and get off the hull.

 

[Reserector_]

I haven't even finished and I've already made a hole in the deck.

 

[Reserector_]

Question, but bear with me while I set this up, please:
This is a stern drive boat which will have an enclosed engine like it did originally. I understand the need for a blower to draw air out of the engine compartment to eliminate fuel vapors.
Originally, from what I can tell, the tank compartment was sealed off from the bilge and the ski locker. I could be wrong about that.
I have noticed that photos of other Caravelle bow riders show a slotted locker cover with the brand logo on it. I figure it allows airflow to the wet items in the compartment.

I'm setting my boat up for air flow instead of a sealed bulkhead. Since my replacement tank is shallower, I am able to raise it off the hull and still have plenty of room. It is longer, so I will lose some ski locker volume, but I'm okay with that. I also left a gap under the center portion of the engine mount bulkhead to allow access to washers and nuts when I bolt the front engine mount in place.
With both the front and rear bulkheads open for airflow, my concern is fuel vapors building up in the entire bottom center section of the boat. My thought is that I need a ventilated locker cover to allow air flow back to the bilge to draw out vapers.
Is this sound logic?
Another thought I had was to add a vent to the bow to duct air into the very front of the ski locker and use a non ventilated cover to force air flow while the boat is moving. Not sure what kind of scoop I would use but it was just a thought.
Your thoughts?

 

[Chris51280]

never seen a scoop to air the ski locker.
You have 2 vents in the aft. 1 cover facing so air gets out and 1 so air can get in while under way. The hoses reach into the bilge area from both vents to make sure you circulate air. The blower is on the "out" vent side sucking air out of the boat. So it blows air out of the bilge

 

[Reserector_]

I get what you're saying, but this boat is not set up that way. All of the vents are in the rear behind the sun deck/engine hatch. Nothing on the side. It's weird.

Here's a picture, but not my actual boat.

 

[archbuilder]

picture didn't upload

 

[Chris51280]

it will work as a venturi principle. The air flow over the vents will create a negative pressure inside the engine cover and suck out air from the bottom through the hoses.

 

[Reserector_]

picture didn't upload

 

[Reserector_]

I was guessing that once started, the engine itself draws a considerable amount of air through the bilge area.

My front intake idea would draft some air through the entire bottom of the boat, keeping it dry (hopefully).
I will at least make a 3" vent hole in the bow part of the floor, under the front rear-facing seat for that purpose. Then, if I decide later to add a small scoop behind the bow light or something, it will be easy to route a hose to the hole in the floor.
Such a hole will be hard to cut once the cap is on, but easy to cover if I change my mind.

 

[Timr71]

Hi, nice work!

I'm joining this resto party for the rest of the way. You need to find some more pictures of your boat and/or get Chevy to share with you all the vent routes into the bilge. Many boats have front air collectors that route fresh air via hoses into the bilge so not only are the fumes ventilated, but so the engine has air to ingest. Typically, the air collectors are either in the nose of the boat, or around the wind shield, could be forward facing or on the sides. The blower motor moves air and fumes while the boat is stationary. Once underway, there should be a significant air flow created by the movement of the boat and the forced air flow.

My boat, has the collectors on the nose of the boat, and from there, two air pipes run down the port side and then into the floor where they empty into the bilge. I'll see what I can find for pictures.

 

[Timr71]

Here's a picture of a C1750 with a side air vent. Typically, that vent has a 3 inch hose that'll drop air into the bilge. The blower hose can be routed to one side if those are the only two air vents. Blower hoses usually go to one of the rear air vents if the design includes both side and rear vents (sides vents for intake and rear vents for air exit). On some boats, those side vents utilize louvers to better direct air into the hose(s).

 

[Timr71]

Example of side louvered vents for intake

 

[Reserector_]

I have amassed quite a library of photos of this model boat, but the hardest ones to find are the engine area, and under the bow. Those are like finding hens teeth.
If I can find a place to add a intake scoop and hose it to the very front of the ski locker through an opening in the floor, it will flow through the ski locker, under the tank, and into the bilge. From there it would have to exit up and to the rear through the factory openings. The center of my boat would do the job that your air pipes are doing, essentially.

I figure that in the end, it doesn't really matter how Caravelle did it as long as I end up with a sound airflow solution.

 

[chevymaher]

I got a vent like above on each side of the boat. One directs air in. One out. Out vent has the blower motor. Most boats use this set up.

 

[Reserector_]

Here's a picture of a C1750 with a side air vent. Typically, that vent has a 3 inch hose that'll drop air into the bilge. The blower hose can be routed to one side if those are the only two air vents. Blower hoses usually go to one of the rear air vents if the design includes both side and rear vents (sides vents for intake and rear vents for air exit). On some boats, those side vents utilize louvers to better direct air into the hose(s).

Interesting. That is a 1990 model and you are right. It had side vents. Looks like they have been removed in fact.

Mine has rear vents only. (My boat)

Which work like this. (Not my boat

Maybe I can use the blower up front as a pusher and flow air along the bottom center, under the deck, which is open all the way to the bottom of the bilge. From there, it can exit through the holes in the rear. That will allow me to have a sealed ski locker cover and not end up with a mold factory under the floor.

 

[archbuilder]

Chevy is correct, usually one facing forward and the opposite side facing aft. I have had a couple set up that way. Just be careful that in your design you address the gas vapors in the engine compartment / bilge. Mold is one thing, blowing up is another! Its easy to loose focus on the primary issue on boats, just make sure you get the engine area vented. Hopefully you can figure out a design to take care of both at the same time. Maybe have a bigger puller exhausting out the back and a smaller CFM pusher to help vent the ski locker.

 

[tpenfield]

My boat only has vents at the stern. Nothing along the sides. It could be a 1990’s thing, but I’d rather have the more traditional along the sides at least for the intake vent.

 

[Reserector_]

Each pair of holes that you see on the back of the Caravelle open into a box with a single opening to the engine compartment. So we can think of it as one in one out.

archbuilder I think I will definitely use a blower and hose in the rear to exhaust, as would be normal. I think it's required anyway. I really like your idea of additional blowers.

tpenfield It does seem to be a 90's thing. I just wish I knew how it worked. Maybe I will once I get it running. I have a small wind velocity meter that I could take some readings with to help me understand the science of it.

It will be something I can play around with on a rainy day.