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.

 

[Maynard Rupp]

Our crusader engined 36 has a sound that comes on occasionally in idle reverse. You would swear that someone was whistling to get your attention. I talked to a guy who is a highly respected Velvet Drive guy. He has never heard of a whistle coming from their trannys. We did have the reverse gear rattling. He said that is normal gear backlash, but also had me raise the idle rpm to 700 in gear. Carburated engines are impossible to get to an exact and consistent idle speed, but more is better. The higher idle also helps the boat maneuver as the 3 to 1 reduction makes the props crawl.

 

[krazy8]

My 36 has the 370 Cummins motors and i am also using a 22x22 4 blade wheel however my wheels were trimmed about 1/2" . If you have a fax number I could fax you a copy of my wheel specs and you could compare.

 

[Banshee36]

Ok, The noise is not a whine, It is more of a rumble. The cutless bearings are new, the aligment is dead on within 4000th of an inch, Mike Hastings is the bomb. It seem the STB side makes noise around 800 and the port makes noise around 1000. I had the props back-ground last year , noise still there.
What is the damper that was mentioned?
After talking to the prop man this week, the new thinking for propellers is a smaller diameter and more pitch. He also said cutting down the props can get expensive.
So the short of it is I am going to put my spare props on the boat HYTORQ's, in 22X22.5 and see if the noise goes away. If not Ralph, the prop man, is going to ride on the boat listen to the noise and go from there.
Thursday I am going to see if there is an erosion of bottom paint to see if the props need more clearance.

FYI, With the Austral's on my rig now , I get the wot of 2850rpm's and 33kts speed, gps.

I also am replacing the Starboard rudderport with a new on, broke one last year and replacing the rudders.
Thanks for the input, but please someone tell me waht a damper is/
Thanks, JW

 

[Genesis]

The damper is on the front of the engine.

 

[jim rosenthal]

You get 33kts? Where's the smilie for "jealous"?

 

[Banshee36]

Sure doesn't everybody, You cant stand up in the thing, everybody sits on the floor, the keel walking is horrible, but its still 33kts, though loaded down she only goes about 29 to 30, wot. the new QSB 425's would be down right scary, almost like my donzi with the stock propeller.

Ahh I see the damper is a harmonic balancer.
Thanks for that. i will update this spring when we trouble shoot.



Off to Cabo inthe Next week for a little R&R .
JW

 

[captddis]

I meant the damper plate for the trans.

 

[Fat Boy]

I, also, have Cummins 370 hp, and only get 27-28 knots, WOT. WOW!!!

 

[Mike36c]

Yep, my girl did 30kts on the first trial runs after the repower (no salon furniture, minimal gear, etc.) now its around 27 with two inches less of prop pitch.

 

[jim rosenthal]

I want to borrow your boat, JW. I will refill the tanks when I am done. I want to see if I can make Norfolk in six hours. Just kidding