Is this exhaust shutter noise?

[natemoore]

Hello, all. It's beautiful here in N.W. Florida, highs in the 70s. We're going camping in Niceville, FL, and we've decided to take the boat and get in some fishing on Choctawhatchee Bay.

I've been curious about this metallic clacking noise my engine makes at certain RPMs, and have always assumed it was the exhaust shutter rattling around. Today, I noticed that it got louder as I raised the outdrive, and quieter as I lower it. I've got an exhaust tube, not the exhaust bellows, and it's not closing around the tube, so that's not the reason for it getting louder or quieter.

All the u-joints and the gimbal bearing are about 3 years old.

 

[Grub54891]

Re: Is this exhaust shutter noise?

Can't tell from that video,to much other noise.

 

[natemoore]

Re: Is this exhaust shutter noise?

Can't tell from that video,to much other noise.

It's the metallic clank on the top end. I can hear it.

 

[Don S]

Re: Is this exhaust shutter noise?

No, and put the drive down some more. Typically you will only hear the shutters ligtly clicking at low idle rpm, not at higher rpm. The exhaust holds it open at those speeds.

 

[ktbarrentine]

Re: Is this exhaust shutter noise?

I noticed that it got louder as I raised the outdrive, and quieter as I lower it.

Just curious as to why you think you need to raise and lower the outdrive while on muffs. I always set the drive so there is the least amount of U-joint action (i.e. drive shaft level). I also don't run in gear on the muffs, either. I am thinking your noise is u-joints. When is the last time you inspected your bellows and lubed the u joints? "3 Years old" doesn't tell alot about the usage or annual inspections on a SW ran Alpha 1 drive... just sayin.

 

[EddiePetty]

Re: Is this exhaust shutter noise?

The noise that I'm hearing is the shift dogs skipping over the shift plate because the out drive is not fully in neutral. Note how comparatively slow the prop is turning in relation to apparent engine speed....just say in'.

 

[natemoore]

Re: Is this exhaust shutter noise?

Just curious as to why you think you need to raise and lower the outdrive while on muffs. I always set the drive so there is the least amount of U-joint action (i.e. drive shaft level). I also don't run in gear on the muffs, either. I am thinking your noise is u-joints. When is the last time you inspected your bellows and lubed the u joints? "3 Years old" doesn't tell alot about the usage or annual inspections on a SW ran Alpha 1 drive... just sayin.

Well, I'm doing a functional check of everything, so I raised and lowered the drive a little while I was letting the engine warm up. I can't really set the drive all the way down unless I get out a shovel and dig a hole. I remove, inspect, and lube the outdrive yearly. I also check the gimbal bearing alignment and replace the water pump impeller annually. Everything works and looks normal. I've done these procedures every year since I replaced the u-joints.

 

[natemoore]

Re: Is this exhaust shutter noise?

The noise that I'm hearing is the shift dogs skipping over the shift plate because the out drive is not fully in neutral. Note how comparatively slow the prop is turning in relation to apparent engine speed....just say in'.

The prop is turning because of hydraulic friction. A pinky finger will stop the prop. If you're saying its the same noise that you get when you shift into gear, I don't think it is. You'd have to hear it in person, I guess, but it doesn't sound like the same noise to me. I should be able to replicate it by shifting into gear really slowly. I know that sound and it's different from what I'm hearing here.

It seems to have a resonant frequency somewhere around 2500 rpm. At idle, it's absent, and at higher rpm.

It is an old, outdrive, though, so maybe you're right. It could be gears clacking.

 

[jze1212]

Re: Is this exhaust shutter noise?

Lower RPM's and throw in a misfire every now and then and you'll hear them flapping away. Bring the RPMS up and you should not hear any flappers..

 

[EddiePetty]

Re: Is this exhaust shutter noise?

. ......I noticed that it got louder as I raised the outdrive, and quieter as I lower it. I've got an exhaust tube, not the exhaust bellows, and it's not closing around the tube, so that's not the reason]

Upon further review.......

Watched your video several more times and am still not ready to totally dismiss the shift dog notion, however, I did notice the odd pattern of cooling water discharge and presence of steam (in sunny, warm Florida?) from your out drive, especially the idle ports.
Perhaps, just perhaps, a component of your now former exhaust shutter is rattling in either the transom or out drive passages. I'd pull the out drive just to see!

 

[natemoore]

Re: Is this exhaust shutter noise?

Upon further review.......

Watched your video several more times and am still not ready to totally dismiss the shift dog notion, however, I did notice the odd pattern of cooling water discharge and presence of steam (in sunny, warm Florida?) from your out drive, especially the idle ports.
Perhaps, just perhaps, a component of your now former exhaust shutter is rattling in either the transom or out drive passages. I'd pull the out drive just to see!

It was chilly when I made the video, probably 40 degrees. Hot exhaust gases + water + chilly, dry air = steam, even in Florida. I'll be pulling the outdrive soon to replace the trim switches, so everything will get a check up. I smoked the exhaust shutter a year or two ago when the water hose between the outdrive and transom pulled loose. I've since made it a habit of checking the water discharge at the bottom of the transom assembly to make sure hot water is coming out. Keep in mind that I have an exhaust tube, not an exhaust bellows, so that may be the odd pattern you're seeing.

Is a rubber coated piece of sheet metal going to clang that loudly if its sitting inside the exhaust pipes or the lower unit?

I have a mechanic's stethoscope. Think I'll probe around to try to isolate the noise and report back.

Thanks.

 

[TilliamWe]

Re: Is this exhaust shutter noise?

I am not sure what that sound is, but that ain't shutters.

 

[EddiePetty]

Re: Is this exhaust shutter noise?

It was chilly when I made the video, probably 40 degrees

. Keep in mind that I have an exhaust tube, not an exhaust bellows, so that may be the odd pattern you're seeing.

Is a rubber coated piece of sheet metal going to clang that loudly if its sitting inside the exhaust pipes or the lower unit?

I have a mechanic's stethoscope. Think I'll probe around to try to isolate the noise and report back.

Thanks.

40 degrees in Florida?!?! I would have thought you would have hibernated by now !!

Remember, the internals of the shutters, the cross pin and mounting clips are metal....no telling what is left and where they went until the drive is removed.

So noted and considered on the exhaust tube.....though I would still expect more water from the idle ports.

Why not just pull the drive and eliminate half the noise sources?

Just sit tin' here think in' 'bout ya.

 

[natemoore]

Re: Is this exhaust shutter noise?

Before we left on our trip, I put the muffs on, lowered the unit all the way down pretty much, ran the engine at 2000 rpm in neutral and in forward, and listened with my mechanics stethoscope. There were no loud clattering noises this time, and no unusual noise coming from the transom unit or the upper half of the outdrive.

There was a ringing sound that I can only describe as one of those old Big Ben alarm clocks with the metal bells coming from the lower half of the outdrive. That ringing sound was there when it was in neutral and in gear. No difference in the sound.

We took the boat out on Saturday and Sunday for a few hours. Everything worked great. I've noticed now that I'm burning 100% gasoline, I may have to switch props for the second time (switched once after I rebuilt the engine) because at about 3/4 throttle, I'm at WOT rpm.

Off topic: So you get worse gas mileage with it. You get less horse power with it. It is harmful to some engines (especially small engines). It makes food prices go up world wide. Yet we're still having ethanol shoved down our throats?

 

[Don S]

Re: Is this exhaust shutter noise?

We took the boat out on Saturday and Sunday for a few hours. Everything worked great. I've noticed now that I'm burning 100% gasoline, I may have to switch props for the second time (switched once after I rebuilt the engine) because at about 3/4 throttle, I'm at WOT rpm.

If you were to get the boat propped correctly, you would get more speed, better mileage, and better overall performance.

With hitting WOT at 3/4 throttle, you are missing a lot.

 

[natemoore]

Re: Is this exhaust shutter noise?

If you were to get the boat propped correctly, you would get more speed, better mileage, and better overall performance.

With hitting WOT at 3/4 throttle, you are missing a lot.

That was only this trip with 100% gas. Before, I could firewall the throttle and stay at max WOT. What a difference the gas made.

 

[Don S]

Re: Is this exhaust shutter noise?

You must have some other issues with your engine. I've been around too many marine engines over the years, and have never seen that kind of differences in how they run compared to what gas they have.