36 Hatts with the 330 Cummins

[Banshee36]

I have a noise issue when trollingat about 900 rpm. I have the 330's whith 1.5:1 Twin disc gears. Swinging a 22X22.5 Austral 3 Bladed prop. I think I have too much prop on her, I only have about one and One half of an inch from the blade tip to the bottom of the boat. Boat runs awesome, just if i need to troll faster for the Tunas, she makes a horrible noise, Not a whine.What are you guys running? How's your speed and fuel consumption?

[captddis]

If it is a clattering noise it is the damper.

[Mike36c]

I have the same set-up using TD 5055a @1.5:1 6BTA 330hp. My props are 22X20 4 blades and I have no issues with noise at any speed. Could it be a loose rudder arm or bushing causing some kind of vibration and not the trannys?

[jim rosenthal]

JW, did you always have this noise or is it new....if it was always there, it may be cavitation or drumming from the small clearance. If new, I would more likely suspect a strut or sterntube bearing. Can you tell if it is one-sided or not...

[Genesis]

BTW my boat has ALWAYS done this in reverse. There is no problem with the cutless bearings or struts - its just an interaction between the wheels and the hull when in reverse at low speeds if the RPM and speed are just "right" - its some kind of resonance.

I've never had it happen in forward.....

[SeaEric]

I sea-trialed a Carver with the 330 Cummins in it a few years back. The engine that had the rotation reversed in the tranny made a noise at low RPM. The noise was from the transmission and was described as "normal" to the buyer, who didn't walk, he ran away from the boat.

[Genesis]

Yeah, that's not normal.

[Walter P]

Strange as it seems, I think you may have the same "problem" that I did on a previous Hatt. At about 850 -1000 rpm I had a very errie whine. (the boat not me). Using a stethoscope on the transmission and other areas, it was definitely in the drive system. After going nuts asking everyone whom I thought may have the answer, I finally got the correct answer from my prop shop. Apparently the props were the culprit. The edges needed to be filed just enough to break the sharpness. It worked, but it cost me a haul out.

By the way, I was told that it would not hurt anything if I left it alone until the next haul out, but it really is unnearving. Check it out it's an easy fix.

Walt

[dsharp]

Dear Banshee, I don't think the clearance is causing the noise. An inch and 1/2 is alright, I wouldn't want much less though. With respect to too much prop you need to be concerned with the engine being able to reach rec. rpm at full throttle, full of fuel, etc. You can't really go by speed for other boats since there are so many variables. As a ballpark figure a reduction of one inch of pitch will increase rpm 200-300 rpm. I haven't run your particular set-up but there seems to be others on this sight that could get you in the ballpark. A 4-blade prop will generally run smoother than a 3-blade. It's not unusual to knock an inch of pitch out as the owner adds more weight. It would help to know your max. rpm. Gears will often make a backlash noise at very low rpm. Alot off times idle gets set too low to make the boat shift smoother. I wouldn't think 900 would be too low, though. Sounds kind of like a chain rattling. Velvet drives are worse about the noise than twin disc gears as a general rule.

[REBrueckner]

"horrible noise" isn't likely to get you the specific answer you seek. An analogy often helps such as " loud beat like a drum"....Did this just start...a new and different noise??
Is this high pitch,low pitch,steady, varying, intermittent (clunking), on one engine or each engine?? ANYTHING you can describe will aid analysis from a distance. Any potential problem will large diameter or incorrect pitch is not likely to be present at low speed...those issues would manifest themselves at high RPM and speed, not trolling speeds. Any other description you can provide??
Absent any other descriptive information I'd guess a damper is the cause also.