Linning up prop shaft with velvet drive

[larryeddington]

Holy crap you are scaring the bejezzus out of me. I a fisint to pull both engines and replace with fresh 318s in my F28. As it is on the hard my intention is to mark all attachment points in the boat and bolt the mounts as currently addjusted back to engine and transmissions. They should be close to where they are now (assuming they are currently correct) however I am going to have a mech check when I wet er down.

I am going to check it after reinstall just to see how close it will be, Engines pretty much have bolt holes put in the same place.


Larry

[prowlersfish]

Doing this in the water will make it harder to align properly as there are easy things you can do on the hard.

I understood that doing the alignment in water was the preferred method as blocking often does not support the hull and gear in the same attitude as water. Am I incorrect in this view

Doing a full alignment in the water is fine, if you have a trained mechanic down in the bilge while underway.
On a new install I like to start the alignment on the hard because its a lot easier to check it by the prop shaft and the prop itself. Mis-alignment shows up much better at the prop since its farthest away from the tranny. .030 at the flange shows up almost to the naked eye at the prop. I do fine tuning in the water, both in the slip and under load at 1500 rpm.

Ron

WHAT ?? its checked at the flange with a feeler Gage in the water of course is best , and not right after launch

[jav]

I understood that doing the alignment in water was the preferred method as blocking often does not support the hull and gear in the same attitude as water. Am I incorrect in this view

Doing a full alignment in the water is fine, if you have a trained mechanic down in the bilge while underway.
On a new install I like to start the alignment on the hard because its a lot easier to check it by the prop shaft and the prop itself. Mis-alignment shows up much better at the prop since its farthest away from the tranny. .030 at the flange shows up almost to the naked eye at the prop. I do fine tuning in the water, both in the slip and under load at 1500 rpm.

Ron

WHAT ?? its checked at the flange with a feeler Gage in the water of course is best , and not right after launch

Paul,

this would be funny if there wasn't so much misinformation. Even Pascoe makes some rather reckless statements about shaft alignment and all it does is confuse the issue.

[prowlersfish]

I know . funny I just read Pascoe's coments

[guglielmo6160]

wow,, I tend to agree, with the water method, being thats where it is going to operate doing its thing. and to be clear, the only thing that was replaced was the engine and drive, the shaft as far as I can see is the original and dont see why it would not be in its correct postion,
however I will check being that a new gland, stuffing box etc was replaced
one more thing I need to add, the boat has been in the water, for a while and there is some growth on the shaft, and of course it was pushed down towards the rudder assy. before I even attempt to slide it back, I already made arrangements with a diver to get under there and clean it up before I slid it back up into position
I do know a little something about mechanics guys, just not marine,
just want to be sure Im not missing something . I understand about not putting stresses on shafts and bearings etc, but wasnt completely sure about setting this stuff up,
whats also important Im assuming is that the shaft itself is true and not damaged in any way
I also assume the cutlass is not roller, ball or any other type of bearing of that sort, is that correct? as I have never had one out
what material is used to create a bearing surface for the shaft?

[Big D]

Some good points here. I start on the hard. Don't know what the vessel has been through in the past so need to check strut bearing to tube alignment as mentioned. Do initial coupler alignment on the hard, splash, let sit for a day or two, then final alignment. Rotate coupler 90 deg. at a time and read.Then do same with tranny flange. If there are differences in the readings, one of them are warped. Don't allow more than .003 out. One thing not mentioned that I think is important is that if there is no intermediate strut, the shaft's wieght will make it drop a bit at the tube, so find the center by noting where it rests on the bottom of the tube then lift 'till it hits the top. The middle of the two positions is where it should rest when aligned. Finally, don't rush the process, don't say "good enough" if it's not in spec because you don't want to bolt it up and have to do it all over again after a bad sea trial.

[Big D]

Bearing is stationary and made of a hard rubber in a brass sleeve.

[guglielmo6160]

thanks again for all the advice[img][img]http://i362.photobucket.com/albums/oo63 ... 3_1885.jpg[/img][/img]

[jav]

Guglielmo-

I appreciate anyone looking to better understand the hows and why's of anything so let me give you my .02c.

You are correct that if only the engine and gear have been changed, the shaft and strut locations should be fine with a few exceptions- 1) the shaft and flange must be in good shape ie- not bent with the flange true to the shaft. 2) the Flange needs to end up very close to where it was with old engine to maintain both alignment with the strut and correct prop overhang. I shoot for overhang to be equal to 1 shaft diameter but even 1.5 times the shaft diameter works but avoid going more. 3) the shaft should start and remain close to the shaft logs natural unloaded center (the stress free position).

From there- your job is to align the engine and gear to where the shaft needs to remain by moving the engine and gear as a unit. The easiest approach (using feeler gauges) has been described but if anything doesn't make sense- ask -don't guess.

[Big D]

I probably don't have to tell you but for the benefit of others, the mating surfaces should be cleaned up, I see rust on them. Should of course be done without taking off any material but the rust.

[guglielmo6160]

believe it or not, all those items are new, its just surface rust from geting wet,
and yes thats important,
Im a little nervous about the growth on the shaft, I have a feeling , Im going to have to pull it to make sure its clean, right now I wont dare try to pull the shaft closer to the velvet drive flange , I have an underwater camera and the diver is reputabable and says he has done this before,
so I will see how that goes, but if the shaft is badly grown over I will do a short haul to service all of that running gear

[rossjo]

Can you borrow a trailer ?

[Big D]

Ditto, you have to dissipate the heat.

OOOps, meant for your other post re tranny oil cooler.

[guglielmo6160]

I really dont know anyone here, so I would probably opt for a haul at a local marina if I need to, but I have plenty of other stuff to do prior to that
Im hoping it will go smoothly, I mean after all, Im not flying to outer space, it is a drive shaft on a boat,
compared to what I do everyday, I think I should be ok,
(that sounds so conceded dosent it?)

[rbcool]

Of Course using feeler gauges is the best way
Maybe I should have written a 2 page description about exactly what we go through when we replace drivetrains

I wish I knew where that Stargate was

Ron