Finding the waterline while inside the boat

[ILikeRust]

So everything about exhaust systems and plumbing, etc. all depends on whether certain elements of your system is above or below the waterline and how far it is above the waterline.

Specifically, I'm looking at the ABYC standards that Neil posted:

http://www.moyermarine.com//forums/attachment.php?attachmentid=4344&d=1312054852

How the hell do I tell where the waterline is in relation to my exhaust manifold?

I'm guesstimating from inside the boat approximately where I *think* the waterline is, but I'm not sure.

Of course, it's easy to tell outside - just look at the boot stripe - and I know where the water hits the stripe, give or take an inch.

But how to I translate that when I'm down on my hands and knees on the inside of the hull and my head bent over the engine? I'm pretty sure it's below the waterline, or at least very close to it.

Based on the last drawing on page 10 of that attachment, I'm concluding I need to lower my waterlift muffler, but I don't know how I'm going to do it - I might simply not have the space to do it. Plus it's a real bitch to get at anyhow - it's in a tight spot, buried about as deep under the cockpit and gas tank as you can get.

But right now, the intake for the waterlift muffler is a little bit higher than the flange on the exhaust manifold.

And the hose leaving the waterlift muffler definitely does not do that big, tall loop shown in the drawing - it pretty much just angles upward and goes directly to the through-hull in the transom.

Then there's this one, which looks a little different:

http://www.moyermarine.com/forums/attachment.php?attachmentid=4351&d=1312185686

There, the waterlift muffler is slightly higher than the exhaust manifold, but there is a big riser between the engine and the muffler. I don't have that either.

SIGH... it never ends...

[Dave Neptune]

Water line

Bill, you can disconnect the intake from the pump and (you may need to add a bit of hose) and open the valve. If you are above the water line no water will come out but as you lower the hose the water inside the hose will be at the water line, when it runs out your low.

Dave Neptune

[ILikeRust]

How do I do it while the boat is on the hard?

HA!



I'm thinking what I'll do is measure down from the companionway hatch to the waterline on the outside of the boat, and then measure from that same point inside the boat.

I'll figure it out, one way or t'other...

[TomG]

Bill,

Just use a water level.

Get a piece of clear vinyl tubing, run it through any through-hull, tape the open end on the outside of the boat right at the waterline (or wherever you want to measure from) and then fill the tube with water. Whatever the water height is inside the boat should equal the height outside.

[Dave Neptune]

On the hard

Bill, can you bring a hose up from the bottom through a through hull? If so attach a clear hose to the bottom of a bucket and hang the bucket over the side with the water level at the W/L and the same principles will apply. Both ends of the water will be at the same "level" and you can see where it is through the clear hose. I have done both of these many times.

Dave Neptune

[ILikeRust]

Yeah, I actually thought of that yesterday, but I realized there's no way to get the hose through the hull. I no longer have any open through-hulls.

Well, maybe I might be able to get a small-diameter tube through the raw water intake through-hull.

I'll figger it out, I'm sure...

Thanks!

[Marian Claire]

Maybe use a Laser level. Set it up high and measure down to each part you want to check. Dan S/V Marian Claire

[ndutton]

Could you use a thru-hull as a benchmark? It is visible both inside and outside the hull. With a long level and a tape measure on the outside you could determine how far below the waterline the thru-hull is located and transfer that measurement to the inside of the hull, again using the same thru-hull as the measuring point.

Accuracy depends on how level the boat is blocked in the stands.

[ILikeRust]

Could you use a thru-hull as a benchmark? It is visible both inside and outside the hull. With a long level and a tape measure on the outside you could determine how far below the waterline the thru-hull is located and transfer that measurement to the inside of the hull, again using the same thru-hull as the measuring point.

Hey, that's a pretty neat idea.

I had envisioned laying a long board across the companionway hatch opening and measuring down from each end to the waterline on each side. Then I would drop a line down from the middle of the board, inside the hatch opening, to that same vertical drop.

Your method seems quicker and easier and likely sufficiently accurate.

I think I might need to grow an extra arm or two to do this, though...

[ndutton]

I think I might need to grow an extra arm or two to do this, though...

Nah, one hand for the level, the other for the tape measure.

[jhwelch]

Hmmm, how about if you had 2 strong magnets -- you could put one outside on the waterline and "find" it using the other one on the inside.

[ILikeRust]

Hey, now you guys are getting really creative.

I know!

How about if I drill a hole through the bootstripe on the outside, and then look for the drill bit poking through the hull on the inside!

[Marian Claire]

That's one of the nice things about a laser level, one person operation. Level,tape and some simple math and you can get the relative elevation of any point on the boat. Dan S/V Marian Claire

[domenic]

Rust, put a 2"x4" across the cockpit with one end over the side. Drop a plum down to the water line. Buy a $2.00 laser. If you can't find one just ask any kid, they know where to get them. Open the cabin doorway. Set the laser on, or under the 2x4. Shine the laser through the cabin. Mark the spot the little red light hits. Now run a thread from the 2x4 to the little red dot. To find the water line anywhere along the inside of the boat, drop a plum from the thread...go port, or starboard, and that is where it is.

Hope this helps.

Note: If you shine the laser at an aircraft, or police car...you will have a bad day.

[domenic]

I see Clare already suggested the same thing.