36ft Hat Related Question

[Jackman]

While I was checking on my Hat I met another fellow Hat owner. He had a mid to late 60's model that had a ton of work done on it. Looked awesome. He also had a set of 330b's installed this year as well. He's been having vibration problems. Said he had the props checked (3-bladed nibrals), the shafts balanced and the cutlass bearings are new. With the old engines he had no vibration problems. (He used the same shafts 1.5" aquamet 22 about 8ft.

What puzzled me is that the props are perfect as per his prop guy, the shafts are the same and balanced as well as straight....ect. The old engines even turned similar rpms according to him. He thinks the only thing he has left is to install a second strut between the current one and the shaft log. Anyone have to do this in a 36ft conversion? He thinks its because the shafts are borderline for the torque of the engines. I say if it worked at the same rpms as the older engine its the prop.

Any clues on this one? I know I gave you little info to work with but you guys are pros!

 

[the kuz]

We have the same set up and 3 blade Michigan nibrals, with no problems. Did they check/tweak the shaft alignment with the boat back in the water after the re-power? Did he get new engine beds? Checked/lapped he prop installation to make sure the key is not binding? I'd start with the alignment - think I remember a thread here describing how to check. Good Luck, and let us know what fixes it. Regards, Bob K

 

[Mike36c]

Jack, describe the vibration: Does it happen only at idle, in/out of gear? Is it worse underway? At specific RPM's? Is the lazarette hatch vibrating like crazy underway? Maybe just one engine?

 

[REBrueckner]

Good check: run first one engine then the other in gear at several RPM's to determine if one or both drive trains have vibration. Recently "balanced" props sometimes are worse than before the "fix". Not always easy to decide if engine alignment/shaft/struts or props are at fault....first step is to see if one or both drive trains are at fault....

 

[BUSTER]

Dittos to the above posts,but a couple of questions.Are the props a bigger diameter thanthey were? Are they pitched oversquare?

 

[Akyla]

The shafts are adequate for the 330b power. He is wasting effort to do an intermediate strut and I doubt it could be easy to do anyway.

If he is shaking then he needs to realign after a check the engine mounts for both solid connection to the stringers and watch them for excessive flex under load when running. Sometimes the threads in the plates in the stringers give it up and need a recoil to hold the mounts tight. If they can't be held tight to the stringer then all alignment efforts are wasted underway. Unless it is bent it isn't an issue of the shaft size.

 

[Jackman]

From what he's told me he says the vibration only happens at higher RPMs. I told him what Akyla has said about the shafts being adequate for 330b's and that I did not think he needed another strut. I forgot to ask if he has had it realigned since in the water. He has virtually the same setup as me with my 32er so I don't believe its the shaft or props (if they were redone properly by his propguy.)

I don't know for sure if they're pitched oversquare but they probably are after seeing them. 3-bladed pitched over square probably could cause shaking. The first thing I asked is if they were nibral because I know bronze blades flex from diesels torque but he said they're nibral.

Could it be fuel starvation underload at higher rpms?

By the way...I highly recommended this site to him and said that he could not go wrong posting any questions he may have. The boat was named "In Too Deep" out of Lewes Harbor Marina Lewes, DE. He may post...

 

[BUSTER]

Oversquared three blades will quickly vibrate,if alignment is not perfect.Too large a diameter prop will as well.The shafts are more than adequate,intermediate struts are not necessary for that length and ruining the cockpit to lift the tanks to install them?The sequence of diagnosis is to break the coupling first and check the shaft alignment,then work his way back to the props. good luck Tony

 

[SeaEric]

Just a thought- Is there a "too close for comfort" clearance issue between the diameter of the wheels and the bottom of the boat? This can cause vibtration at higher RPM's.

 

[captddis]

Eric beat me to it but I bet it is turbulence and not vibration. Measure the distance from the tip of the prop to the bottom.

 

[Jackman]

I'll have to check when I'm down checking on my boat. I know he does not have pockets like I do so he can't be too close but I'll measure it. The rule is no less than 10% the diameter of the prop from the tip of the prop to the hull at its closest point, right? I almost think it might be the "over square issue". Thanks for the help so far.

Funny thing was when I was talking to him he asked me how I knew so much about boats...I guess because I was much younger than him...I said since I had my first car none of my vehicles have ever been to the garage...except to get tires...the same goes for my boats..they've never been to the marina. Helps to be able to learn from a mechanically inclined Dad. Thanks Dad if you read this!

While we talked we touched on a lot...he wanted to get his bottom done and the yard guy mentioned his cousin's sand blasting business...Right away I said to not go with the sand, use soda blasting and explained why. Of course we walked back and took a look at my boat. He commented on how nice it looked and of course I said "it's a work in progress!"

Thanks for the pointers again. I'll pass them all along to him.

 

[Banshee36]

Is this boat , with the vibration Issues a 34 HATT in Lewes DE?
JW

 

[Jackman]

I never asked the exact model but its no less than 34 (bigger than my 32') and yes, its in Lewes, DE. I'm not good at estimating the exact length...only relative to my Hat is was bigger. Probably a 34....I misjudged it as a 36 most likely. Any insight Banshee?

 

[Mike36c]

Jack, He may have a 34 footer as my 36 came from the factory with two struts per side. In addition to all of the above look into what changed during the engine swap. New raw water intake wedges causing turbulence? Maybe a new transducer? I normally run 4 blades but when I run my spare 3 blades I notice considerably more vibration, the 3 blades have no cup. He must have changed wheels during the swap, compare prop diameter/pitch to the old wheels. Maybe throw the old wheels back on and see what happens.

 

[Banshee36]

The name of the boat is In reel Deep, Carl owns the boat. Really nice guy and did a spectacular job of redoing his 34 Hatt. If its the same guy. I have not seen his install job,but Have heard that the engine beds are agged to the stringers and all the lags are loose after running. I think He cut the stringers, not sure exactly what he did after that. But I am fairly certain it has to do with the engine beds.
He keeps his boat at my marina in OC, I just have not had the time to go over and check it out. I have my hands full with my new rig( non Hatteras but gbuilt in Harkers Island.

JW

 

[Trojan]

He needs to define the problem better. The type of vibration, when it occurs, the rpms, where he feels it. It could be any of the things suggested.

BILL