Luhrs 28 with single 454 V-drive

[7228sedan]

I recently took ownership of a 1972 28' Luhrs sedan bridge. The boat was repowered a while back with a Mercruiser 454 coupled to a Velvetdrive 72 V drive. It has the 1.5:1 ratio in it. I have not run the boat yet as the transmission needs a rebuild due to bad bearings in the V drive. I am concerned that the ratio is not correct for this size boat. Does anyone have any experience with a similar combination?

[gonzo]

The ratio looks OK. What diameter prop do you have?

[7228sedan]

I have'nt checked out the prop yet. The boat is being hauled to my yard on 11/17. I have alot of experience with sterndrive boats, this is my 1st inboard. What size would you expect to be on there?

[gonzo]

On a sterndrive with that engine and a 1.5 ratio the diameter would be about 15". It should be similar.

[7228sedan]

I'm going to take a ride to the yard where she's on blocks to take a look this weekend. I assume that the pitch & diameter should be marked into the prop?

[gonzo]

It is usually stamped on the face of the prop. Diameter is easy to measure with a tape from the center to the tip of the blade.

[7228sedan]

I'll check it out this weekend & get back to you. Thanks for the information!

[mongo75]

On my 440 powered 25' Luhrs, the prop guy told me I would need a 16x16 cupped prop. I too am new to inboard formerly being an I/O guy, and for the engine size I thought the prop is a bit small, but it's a good starting point I guess. Your best bet would be to find a prop shop that'll let you test different props, but it's a pain in the ass when you're not on a trailer, having to dive every time you want to change props.

[7228sedan]

I finaly got around to cleaning up the prop this weekend; it is a Michigan Wheel 17 RH 16. I assume that it is a 17 diam. 16 pitch. Any comments?

[baeckmo]

Stick to that prop. Provided the engine is ok, this is what is needed!

[7228sedan]

I finaly got around to pulling the bad trans & V drive out. Come to find out, it is a 71 series Velvet Drive, not a 72 as I was told. I have a fresh 72 series ready to drop in but I have 2 concerns.
1. the 72 series bolted to the V Drive puts the output shaft coupling about an inch further forward (away) from the propeler shaft. Will I need a spacer for this, or is there a way for me to push the whole shaft inwards to take up the extra space?
2. What is the best way to beef up the mounting beds for the transmission? I saw a post by mongo75 where he had a similar problem. When I removed the transmission, the port trans mount pulled right out of the wood that is through bolted to the stringer. Can I cut out the rotted wood & replace with new? If so what species of wood dould be recommended?

Thanks all

[TollyWally]

I can't help but wonder if a rotted mounting member had anything to do with the bearings going bad in the first place. You may need to do a little bit more than splice in a bit of new.

[Jango]

Since the 72C Trans is about an inch longer than the 71C, in addition to repairing the wood problem, you will need to RAISE the motor/ trans slightly to properly align with the drive shaft - probably less than a 1/4 inch depending on shaft angle.

Shaft length problem can be taken care of by moving engine/trans Aft, about an inch,OR installing a longer shaft or if you're lucky and have more than inch clearance between prop and strut, just pull the shaft/prop forward to match couplings.

[gonzo]

You may need to cut the shaft if the distance from the face of the prop to the cutlass is too long or if it touches the rudder. Otherwise, it will line up the same. The 72 is a bit over an inch longer.

[7228sedan]

I have not yet installed the new transmission, however the shaft does slide in & out of the hull fairly easy. It will easilly make up the difference in transmission length; my question now is, should the shaft slide in & out of the hull? It's not like it goes with gravity, but I was able to push on the prop with my hands & slide it forward.

[TollyWally]

That is a good thing. If you don't feel "wiggle" things are looking up. Good luck with your rot issues etc. You are doing this work at the perfect time of year.

[7228sedan]

Thanks for all the input. I'll post an update when I get the transmission mounted.

[mongo75]

I'm glad that ou guys posted the 72c is an inch longer, because on my 25' Luhrs, I may have to perform some kinda magic to get my 440 & 72c to fit in the same space a 360 & (I'm guessing) 71c was in previously. I'm considering a propshaft spacer and sliding the v-drive back about 6 inches. BTW sedan man- I wound up completely cutting out the old 3/4" stringer, al 15' of it, and replacing it with 2 3/4" sheets epoxied together. If you mount areas are bad, and you don't want to do what I ended up doing, I would neatly cut out the bad part, put new wood in it's place, then put a longer piece on the outside of the stringer, and if possible on the inside to to sandwich it, then glass with epoxy the whole repair.

[Marco1]

I have not yet installed the new transmission, however the shaft does slide in & out of the hull fairly easy. It will easilly make up the difference in transmission length; my question now is, should the shaft slide in & out of the hull? It's not like it goes with gravity, but I was able to push on the prop with my hands & slide it forward.

The shaft is free to slide along it's axle, only the stuffing box hitting the coupling would stop it from coming out
http://www.boatweb.com.au/images/pssdiagram.gif

If your gearbox is longer, the V drive will go forward yet when you push the shaft forward it will go forward and UP and will not meet the coupling in the new position. It seems you will probably need to rise the eninge a bit.

[7228sedan]

That's what I was hoping the case was. I will need to raise the transmission for the geometry to line up, but I'm not concerned with that. I'm installing all new mounts for the motor & transmission. I'm pretty sure the whole problem with the current transmission was a missalignment. The wooden timber that the port trans mount was bolted to was completely deteriorated and crumbled when I removed the transmission. It actually appears that a battery leaked or exploded at one time. The wood looked like it was soaking in acid. If I understand correctly, I need not finish aligning the motor until the boat goes back into the water?

[Marco1]

I the engine mounts are not solid, the whole thing is disaster in the waiting.
From what I know...that is not much...I think that the engine/gearbox/Vdrive can be aligned with the shaft whilst on blocks and of course after all the wood has been replaced/repaired. I don't know why you would wait for it to be in the water unless there is some flex in the hull when it is on land that will change when on water? Could be I suppose depending on the type of hull... Someone else on this?