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View Full Version : 22c w/ volvo duoprop listing badly



d1mbu1b
11-20-2006, 07:43 AM
I just got my boat together for the winter boating season in Florida.
There are several bugs to work out but the most obvious is that it leans
badly over to the starboard

It ran true for the first 5 miles or so and shut down with no problems.

I went back out an hour or so later and the boat sounded like it
was "whomping" and it leand badly to the starboard...
I thought I messed up one of the props.
Got the boat out of the water and both props are present and in good condition.

I have no idea what would cause the boat to start leaning like that when
it was running straight an hour prior.

The engine runs fine out of gear.
I have not yet run it in gear out of the water.
both tabs were always out of the water.
I never needed the tabs for a listing problem before the build.

Here is what is new:
motor: mag350 to 383; so far seems to run strong
drive coupler: purchased used
outdrive: Volvo DPS, bought used w/ a slight bend in the skeg
props:
....larger front prop was damaged on all three blades requiring welding,
....both have been cupped,
....the smaller rear prop was re-hubbed since it was racked out of center.

Are both duoprops in gear all the time or are they setup like a limited slip
differential transfering torque away from the prop that is slipping?
Can a prop slipping on its hub cause listing?

Please advise of any suggestions or ideas, all are welcome.

Morgan's Cloud
11-20-2006, 08:07 AM
I don't want to make anyone sound stupid here , but was there a good crosswind blowing on your second run ?
I really can't see in that short period of time a sudden deflection developing in your bottom or a mysterious compartment in the hull filling up with water.
If your tabs are remaining clear of the bottom you should be otherwise OK.
The duoprop drive rotates both props at the same rpm's all the time .... no slip or anything else ...

d1mbu1b
11-20-2006, 08:29 AM
I don't want to make anyone sound stupid here , but was there a good crosswind blowing on your second run ? ...

Dont worry about making me sound stupid.
I do that well enough on my own.

I suppose it is posible that it was the wind, but it was relativley calm out.
Great idea though, I hope you are correct.

What about the "whomping" ?

Morgan's Cloud
11-20-2006, 09:56 AM
What about the "whomping" ?
I forgot to mention that in my reply ......
Can you describe it in any more detail ?
Where it sounds like it might be originating ... is it an engine noise or is it the hull pounding etc ?

d1mbu1b
11-20-2006, 10:10 AM
When it happenned it sounded like it was coming from the
outdrive and not in the engine compartment. That is why
I thought I lost a blade or something. To me, at the time,
it sounded and felt like something seriously out of balance.

I suppose, like you said, if the boat was listing due to wind,
and there was a chop hitting the hull, it could have sounded
like a "whomping", but the chop on the hull (to me) sounds
like a "thumping" :)

Maybe I was draging a manatee.

I fired her up this morning, run it in gear, w/out the props and
it reved up fine.then I run it in gear with the props and it also
reved up fine, but with a slight added vibration.

Drive oil looks brand new.

Hopefullly, I was overwhelmed with all of the posibilities and
misses the obvious.

One more posibility. The motor is currently seriously retarded.
The builder wants it there until he can get in it on the water
and set the advance.

Maybe a retarded motor under load can cause some of these
symptoms.

Woodsy
11-20-2006, 10:15 AM
Counter-rotating propellers pretty much cancel out any prop torque. If they are mis-timed there will be a serious vibration, but that would have been present right from the start.

Check your trim tabs.... more than likely you "accidentally" dropped a tab...

Woodsy

MOP
11-20-2006, 10:43 AM
You say you had the reap prop re hubbed, possibly it was not the correct one and it is slipping or may have gone completely which would let the props go out of time. I would pull the back prop and look to see if there is signs of rubber peeling/burning where it contacts the prop it's self. Incidentally the prop timing is identical to the BIII & BH drives, I have a diagram & explanation I can email you if you need it.

Phil

d1mbu1b
11-20-2006, 10:58 AM
You say you had the reap prop re hubbed, possibly it was not the correct one and it is slipping or may have gone completely which would let the props go out of time. I would pull the back prop and look to see if there is signs of rubber peeling/burning where it contacts the prop it's self. Incidentally the prop timing is identical to the BIII & BH drives, I have a diagram & explanation I can email you if you need it.
Phil


No signs of burn or torn rubber, but that is
exacly what the old smaller rear prop looked
like prior to re-hubbing.


What is prop timing?
I have been taking the props off and putting the props on willy nilly.

Yes, please do send the diagram and explanation.

What would the symptoms of bad prop timing be?

Thank you

Morgan's Cloud
11-20-2006, 11:38 AM
You say in your original post that after repairs you had the props cupped ..
Do you mean you had them RE-cupped after repairs or you cupped a pair of props that were NOT originally cupped ?
I have'nt seen a pair of DP-S props recently enough to remember if Volvo cups them or not ,
As far as prop timing goes ..... This weekend I spent some quality time with my new Volvo owner's manual for my engine/drive package.
This thing is a tome by comparison with what you get when you buy a black engine and EVERY base is covered . On the prop installation section I clearly recall that there is NO mention of timing the props on the DP-S drive.
I can assure you , that this manual is so comprehensive , that if it was required , it would be mentioned.
Nonetheless , I believe in timing all twin prop units .... Can't really hurt .. besides , the B/H needs it :biggrin:

MOP
11-20-2006, 12:00 PM
Oh Steve:kyle:

Any who back to timing, I ran a BH on my 22 if the props were two or three splines off you could feel it. Kind of stands to reason if one drive needs why would not another. PM me your email and I will shoot you the one for the BH.

Ooops later its on my home machine!

Phil

d1mbu1b
11-20-2006, 12:03 PM
They were cupped for the first time.

Although, it lookes more like a lip than a cup.

d1mbu1b
11-20-2006, 12:09 PM
PM me your email and I will shoot you the one for the BH.
Ooops later its on my home machine!
Phil

Is this it?
http://www.donzi.net/forums/attachment.php?attachmentid=1304&d=1079845190

It is off of one of your old threads.

Morgan's Cloud
11-20-2006, 12:21 PM
Phil ,

I'm not sure I understand your post , can you clarify ?

Thanks/Steve

Forrest
11-20-2006, 04:03 PM
My guess is that you have a "spun" hub on one of your props. The prop hub in question may feel tight by hand and spin just fine with no load while on the hose, but once you put a load on her, the hub just slips. That would explain the listing problem while underway since just one prop is doing all the work. Volvo Duo-Props aren't very sensitive to timing like Blackhawk props are, and besides, a prop timing problem would give you vibration, not a list.

Tony
11-20-2006, 05:13 PM
Forrest has it nailed...as usual!

Regarding the timing of duo-props, the way I've got it figured is that the blades "line up" with each other 3 times per revolution, and the only thing you change with a different installation is exactly where you want the blades to "line up" with each other. I've experimented with my Volvo DPX and have not yet noticed any difference, as Forrest mentioned. Is the BH sensitive because it is a surface piercing setup?


:beer:

d1mbu1b
11-21-2006, 10:37 AM
Thanks guys

I'll line the props up per the suggested installation process and run it, then check to see if its still lined up.

If the prop is slipping, odds are it won't line up.

Is it posible something in the outdrive could be slipping instead of the hub?
The prop's hub gasket thingy looks fine and there are no obvious signs of slippage.

Donziweasel
11-21-2006, 05:25 PM
I am with Forrest. Sounds like a prop might be slipping. The torque of the prop that is not slipping might lean your boat over. Whumping noise could be one of the props starting to slip.

d1mbu1b
12-03-2006, 05:24 PM
I don't want to make anyone sound stupid here , but was there a good crosswind blowing on your second run ?
I really can't see in that short period of time a sudden deflection developing in your bottom or a mysterious compartment in the hull filling up with water.
...

You were correct on both counts.
I am stupid, and a mysterious compartment suddenly filled up with water.

Since the listing, I washed the boat on the trailer and jumped down into the engne compartment to do some re-wireing. Sure enough, there was a mysterious compartment holding several gallons of water.

As for the whomping, that turned out to be a flooding carburetor that won't open the vacuum secondaries. It got flooded out fouled some plugs, and ran rough enough to sound like a whomping. It looked like a scene from Mr. Magoo.

So with out secondaries, the boat cant breath well enough for more than somewhere around 3500 RPM. (the tach isn't working correctly yet either)
I hit 55 GPS !!!!
6 grand later (3 in the motor and 3 for the outdrive) I'm doing 5 mph slower than before I started.

Morgan's Cloud
12-04-2006, 06:40 AM
Boy , just wish I could figure out my own problems as easily :D
I really could'nt see it being anything major as it happened in a very short period of time between two runs.
I looked a bit more closely at my Volvo owner's manual this weekend and it seems as though they only cup the rear prop on the DP-s unit.
Not that it means anything in your case , but possibly usefull to know down the road.
Let us know how well you run when you have everything back up to spec with the engine .
Steve