loud SN

Art. that's a great idea. In fact, that's exactly what it sounds like to me.... a dry exhaust. I will definitely check that out as soon as it gets above freezing.
Buchanan Dam is in the Texas hill country about 50 miles from Austin. I'm 2 minutes from Lake LBJ, 5 minutes from Inks Lake and 10 minutes from Lake Buchanan. Can't ask for much better location than that unless you live on the lake. And around here that means a lot of cash for the home and taxes.
thanks a million for the advice. and thanks to everyone else for your help. i'll let you know what i find.

terminaldegree,
unfortunately you can't carry on a conversation in mine! I'm going to check out the water volume as Art suggested. I really think that is going to be the solution.

Hook 'em Horns! Are you living in Wisconsin? If so, no wonder you miss the Texas hill country! My first inboard was an '79 MasterCraft stars and stripes. I loved that boat but looking back I can say for sure it wasn't built like the Correct Crafts.

Before you do a flow test: It will be a lot easier to just open up the impeller and look at the insides. I am guessing that you'll see the problem immediately. If not, then you could do the flow tests.

I went to school in east Texas (Longview), but while in school got to see the state quite a bit. I miss the people in Texas, but that summer heat can be a bit much. Welcome to the site!

I wonder if you could get louder manifolds by putting the riser gasket in backwards?

Have you tried replacing the exhaust manifold gaskets?

The noise is normal in my boat. I've had two hullhuggers, one original and one replacement, and the same result when the boat is operating normally. To avoid pounding that bothers my family when the water is anything but flat, I need to drive the boat at plowing speed. There is a noise, maybe more tone than volume, that comes from the stern, I believe through the exhaust. It goes away when with more throttle and the boat on plane.

At the risk of sparking hackles from the loud pipes crowd, I would be open to the idea of adding another muffle if it made sense. Even with my otherwise quiet boat, my need to ski at 6:30 a.m. is often noted by my neighbors, even those who have no reservations about fire pits and tunes until early into the morning.

First, thanks to everyone for your responses to this issue. I really appreciate it and am proud to be a member of this group.

Now to answer some questions from previous posts:
1. The flapper on my single exhaust is in good shape.
2. The exhaust gaskets appear to be installed in the proper position although I couldn’t determine if they’re flipped front to back. I could not see the tab that Art   
    referred to. The stamped labels are on the outside so I would think if the gaskets were backwards the lettering would be toward the engine and not legible. It is
    worth noting that the previous owner replaced the exhaust manifolds. Not sure why unless they rusted out.
3. I replaced the hull hugger right after I bought the boat. The baffles in the old one were broken off possibly due to the lack of water in the exhaust. So maybe
    this problem has been going on for a while.
4. Yep, it’s hot here in Texas. But while a lot of people around the country have stored their boats for the winter we’re still on the lake. My wife and I and the mutt
    took three boat rides in February in 80° weather. The water was like glass. Great footin’ water!

Today I tested the amount of water getting through the engine as suggested by Art. Rather than let the water pressure from the faucet affect the results, I ran the hose into a large bucket and put the intake hose from the pump into the bucket. That way the pump is actually sucking the water instead of the hose forcing it in. Running at 1200 rpm the engine was pumping five gallons of water from the exhaust in sixty seconds and for what it’s worth the pump sucks five gallons of water from the bucket in sixty seconds (seems reasonable that in intake and exhaust are the same). From what Art says I should be getting about three times that amount of water from the exhaust so hopefully this is the problem and should be easy enough to resolve if I can determine what it is. The impellor is a Sherwin with some wear but it doesn’t look bad enough to prevent it from pumping properly. I assume that if it were installed backwards it would flip itself over as soon as the engine was cranked. Or would the “tabs” just break off? I checked the the thermostat it appears to be okay or at least it’s not stuck.
So there you have it. Not sure where to go from here.
Thanks again.

Oh-oh; I must not have been clear with my instructions. The object of the garden hose was to feed cooling water to the engine while performing the test. That way you can run it as long as you want without hurting anything. The garden hose goes in the hose that leads to the thermostat housing, not the one going to the pump. I was also assuming that the boat was floating in the water while doing this, but sucking from a bucket is fine as long as you're sure the end of your hose isn't sucked down against the bottom of the bucket.

60 seconds to fill a bucket is far too long. Something's wrong in your pump system. If you want to call me, PM me for my phone number!

Nah, T stat shouldn't have anything to do with it. Water bypasses that directly into the manifolds because they need cooling water all the time not just when the T stat is open.

Art, your instructions were clear but I thought if the pump was sucking the water I'd get a more accurate result. I had the water hose running in the bucket at the same time the pump was sucking water so there was never a time when the pump wasn't suckling water. I had the end of the pump hose attached to a piece of angle iron the keep it from touching the bottom of the bucket. I'd love to talk.
Derris Lanier
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crap! I meant Sherwood. Must've been thinking about paint!
I'll go check these gaskets. I was looking at the exhaust manifold gaskets at the engine not on the top.

Again, the amount of water out the exhaust will not change no matter what is going on with the thermostat.

water in = water out

Thermostat only tells the water to go through the block first or not. If cold water goes in the block hot water exits. If not, cold water goes right out.

You are not sucking enough water. Your system appears to be functioning at about 1/3 efficiency.

What are your operating temps?

Start with the easy stuff, with a nut driver follow the raw water intake from the pickup and tighten all hose clamps, check your strainer gasket and tighten.

The symptoms you are seeing are not indicative of an air leak. Impeller or pump. I'm surprised temps aren't creeping up while under load. Do you ever run the boat at sustained higher rpm?

Derris,
I agree with the new impeller idea. Someone mentioned the exhaust flappers on the tips and their influence of silencing the engine noise. That is NOT their purpose and do not quiet the exhaust.

antique boater wrote: TRBenj wrote: The symptoms you are seeing are not indicative of an air leak. Impeller or pump. I'm surprised temps aren't creeping up while under load. Do you ever run the boat at sustained higher rpm? Just a ski run now and then or an occasional haul ass to the smooth water on the other end of the lake. I've never noticed it going above 160°. But I'm not going to lie to you and say that I always keep an eye on the temp gauge. But I can usually smell the engine when it starts to overheat though.

That doesn't sound right when you say "I can usually smell the engine when it starts to overheat". which implies it overheats regularly.