Prop Clearance?

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MauleOne

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Joined
Jan 22, 2011
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I had to change shafts and props on my 3870. Now the prop is only 1/2" away from my rudder.

*

No interfearence at any rudder angle there used to be more room.

I can move the engine and all ahead several inches. Is it worth it?
 
I think this is a 3870....a Bayliner 3870.
1942297_1.jpg
 
Shortening the shafts is a lot easier and less costly than moving the engine.*** Why where the shafts changed? Most shafts can be straighten?* We straighten thousand of shafts each year.* Do you still have the old shafts?* If there are yards around I would see how much distance is between the shaft and ruder of like boats. *When work is done on the Eagle I am there to make sure its done correctly and/or at least the same as it was.* If not I question it.
 
FlyWright wrote:
I think this is a 3870....a Bayliner 3870.
Sure looks like one to me!

*

This is a bayliner 3870.


-- Edited by SeaHorse II on Tuesday 21st of June 2011 01:32:52 PM
 

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MauleOne wrote:
I had to change shafts and props on my 3870. Now the prop is only 1/2" away from my rudder.

*

No interfearence at any rudder angle there used to be more room.

I can move the engine and all ahead several inches. Is it worth it?
*You didnt say what your original dimensions were....ie how close the shaft end was to the rudder, or what your original prop was.

Sounds like whoever did the job didnt pay attention to duplicating the original arrangement.

Here is a drawing I made of my own prop and rudder. Mine is close too but still 2 1/8" away from the rudder. In my case, I have to remove the rudder in order to pull the prop because of this. Turning the rudder hard over doesnt give me enough clearance.

R.
 

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"*In my case, I have to remove the rudder in order to pull the prop because of this. Turning the rudder hard over doesnt give me enough clearance"

Ooh that ain't good.
 
Yes, that is a 3870 just like mine.

I had to change the shafts when I changed the gears when one of the original gears failed and was o/h and failed again.

I went from the*dropped shaft Velvet Drive*to a ZF 280. The ZF is a much shorter gear.

The shaft diameter is 1 1/2".

I used to have enough clearance that I could remove prop with out removing rudder. Now I have to remove rudder.

I have been dealing with a high rpm vibration.

Now I am going to pull the shafts and have them shortened. You may ask why I didn't do that before, well it means I have to pull the shafts, drive 360 miles home. Have the shafts shortened and the couplings trued and drive 360 miles back to the boat.

On top of that it is a long story that has to do with the engines being changed from Chrysler-Mitsubishi 6 cyl 135 hp to 7.3L V8 International 200 hp diesels by the PO.

I will get it done.

(PS yes I still have the old shafts)



-- Edited by MauleOne on Friday 15th of July 2011 08:44:14 PM


-- Edited by MauleOne on Friday 15th of July 2011 08:54:48 PM
 
Shafts are out and with couplers went to a machinist for shortening and trueing.

During the removal it looked like the alignment was off.

taking the shafts out was a pain because the couplers would not come off the shafts. Had to use the old deal with the extra long bolts and a spacer between the chaft and the coupler. Very slow and awkward but it worked. Will put more anti sieze on them during installation.
 
Shafts and couplers are ready for pickup at machine shop.

Was told that shafts were ok (had them shortened) but couplers were way off and had to have surface cut to true them to shafts.

Also had keyway recut to make up for amount cut off shaft and alighment hole for set screw reinstalled.

Couplings were also too tight and had to be opened up some.

Sounds like part of the vibration problem had been identified.

I will install the shafts today and test run the boat Saturday when the yard can schedule me for lift back to the water.
 
Coupling was to tight? hmmm suppose to be an interference fit, remove, reinstall with heat
 
Coupling are still tight. The machinists knew what interference fit was correct and made the adjustment. Believe me, I had to pull them off with a gear puller.

Reinstalled shafts, props, rudders and splashed boat back in harbor.

Waited till the next day to perform shaft alighment. Alighment not very far off. Only minor adjustment required.

Performed a slow speed run in the Sound to adjust the stuffing boxs. Check their temperature with a remote gun.

Full throttle run next. Good and steady with no vibration.

It was hard work and cost about $1.5K total but now the boat feels good. As the commercial says "Priceless".

Unfortunately the repitching of the props knocked about 200 rpm off the top. Stilll I have a plan to deal with that. The new turbo chargers are sitting on my work bench right now. Just waiting to find time to fabricate some oil lines.

I still have a question about those stuffing boxes, what temperature should they run at?
 
The rule of thumb I've followed has been 20 to 30 degrees above ambient water temp.
 
That sounds about right.

water temp here is in the low 50's so I will look for 70 to 80 at the stuffing box.
 
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