Engine Mounting

I'm restoring a 1968 Luhrs.It originally had a Chrysler 360 with a 72C velvet drive and Walter V-drive. The original mount were two 4x6" hardwood blocks about 6' long, bolted to the stringers. The blocks were carved to fit the different heights of the v-drive and engine mounts. I don't believe the velvet drive was mounted, it just sat between the engine and v-drive. I would like to instead of using two big *** chuncks of wood, use angle iron or aluminum, to mount everything. That way I can mount the V-drive first, and then mount the engine to that. I figure that would be alot easier way to get the proper shaft alignment, and plus it's just easier as a whole.

Could I get some input as to what thickness I would need if I went with aluminum, or it with steel? BTW- I'm putting a Chrysler 440 in it now.

 

Hi Danny, I don't know much about inboards, only the ones in cars. It may well be that the original was standing loose, and it would be to allow for engine vibration - not a very good method, but they may not have had decent rubber mountings back then.

In your new installation, use proper rubber mountings that bolts on the engine and then to your frame, otherwise a lot of vibration will get carried over to the hull.

Allu can get cracked under stresses, which is why it's not used for trailers in general. Iron can take much more abuse. You will have to treat the iron against rust though. Don't know how heavy your motor is and how you plan to form the pieces and what angles you have where - maybe if you make a drawing ?

 

Fanie,
I was thinking about bolting some maybe 1/4" thick 3x3" pieces of 90 degree angle iron to the stringers, and then bolting the v-drive to one section, and the engine to another section. That way once I get the v-drive properly aligned, it's a simple matter of dropping the engine/velvet drive into place behind it. I could protect it by priming, painting, and maybe even a coat of epoxy.

 

You will have to use proper washers so the bolts heads won't want to pull through the stringers, and I would use 150mm long pieces, rather the overkill than under.

You will have to make sure the stringers are capable of the weight and forces, remember you are now point-loading the bolted areas. If you have ANY doubt whatsoever, you better strengthen the areas properly. A couple of bolts to the stringers would improve it some, but it is important that the setup must be strong enough. Rather be safe than sorry.

Do use decent rubber mountings, you really don't want the stringers to break loose ! They shouldn't even be expensive. What's the stringers made of ?

 

The current stringers are 1" plywood, glassed over with roven woving. Since some sections are rotted (not too bad, but not as strong as they should be) I plan on cutting out the rotted sections, replacing them, and THEN adding another 1/2" sheet of plywood to both sides with a good thick epoxy and milled fibers mix, THEN, I will glass over that. So I'll have doubled my stringer strength, and that will be more than sufficient to hold the block. I would figure the engine is about 800 pounds (363 kilos), with another 230 lbs (100 kilos) for the v-drive and velvet drive. Sorry, I don't know the proper metric measurements for the wood.

 

As long as you're sure it's not going to fall through the hull

You guys should switch over to the metric system now, it's much more accurate Even the English have switched... and everything fits for a change.

Besides, a yard is the thing you park the boat in. No two feet are the same size. An inch is something you do when you inch foreward to get in bed after a late night out and you better not wake the wife

Also, if you 1/4" it's going to be daylight before you're in bed ! And what kind of a size is 7/16th good grief ! No man, you US okes must come right now

 

My Engine/Velvet Drive is mounted to my 2 x 6 ash stringers with 4x6x3/8 thk steel angles. Engine is equipped with marine mounts utilizing rubber between the engine and the steel angles. In aluminum, I would use the same size angles except 1/2" thick.
Hope this helps, Jango

 

Thanks for the hard time Fannie LOL, but sorry, I'm good with the US measuring system.

Jango, that's what I was looking for, so I guess my idea will work. I'm sure you both can see how I like the idea of mounting the whole works to 2 separate angles, so it would be easier than trying to get everything to fit at one time.

 

Aligning the shaft with the trans, then hanging the engine will not work Danny. Unfortunately you have to align both as an assembled unit. The trans can hang in space as yours did originally, but mounting arrangements would have to account for the back half of the engine's weight (including the tranny). Most setups do support the tranny, which accounts for the rear of the engine support as well.

Also attaching to the stringers as you've described has me a bit concerned about he point loading at the ends of your repaired areas, with engine/trans combo (read half a ton) hanging there, which is why the 4" x 6" x 6' engine beds where there in the original setup. A steel or aluminum rep[placement for the beds is a good idea, but it's mount needs to be stout, which I don't feel 1" sheathed plywood, even with some 1/2" scabbed on is.

Do you have some pictures you can post? It would make things a lot easy.

 

propulsion

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Par,
I've included some pics below to show what I'm talking about. What I want to do is first install the shaft in a PSS, and then align the v-drive to the shaft and bolt it in. That I believe will take the major cause of vibration out if the equation. I feel it's easier than wrestling all three pieces (eng, velvet and v drive) in place at once. THEN all I have to do is take my pre-aligned and mounted engine-velvet drive package pictured below, and with the help of a gantry, measuring shims (I forgot what you call the damn things to measure gap) and a steady hand, I can bolt it to the v-drive and then bolt the aluminum angles to my stringers. As you can see, I may have over did it on drilling 1/2" bolts holes to mount it to the stringers, but I wanted to ensure I spread out the 1000 lbs of weight evenly. I was also wondering if big fender washers would suffice for back up of the stringer mount bolts, or should I use aluminum back up plates of about 2"x2"? Also- the angles I used are 4"x4"x3/8"

 

Danny, your arrangement looks to work fine. Aluminum is substantially weaker then steel, but more importantly doesn't like vibration much, suffering from fatigue pretty easily. I'd use steel, powder or truck bed liner coated to prevent corrosion. The washers will do fine on the through bolts into your beds. Feeler gauge is the term I think you were looking and put a fresh coat of paint on that old velvet drive.

 

Thanks for the advice Par- and I actully plan on tearing the velvet drive apart and rebuilding it, just to be on the safe side as I don't know it's history. Same with the seals on the v-drive.

 

Danny, I have a 1968 Luhrs, 32ft Flybridge, about 10 years ago, I was at where you are now... I have twin engines and Walters V Drives, When I got the boat, the VDrives were shaking all over the place under power, it was actually hard to belive they didnt fall out of the boat. I had decent stringers, it was just a poor design to bolt the V Drives straight down through the stringers. I had a steel shop make up two "L" shaped brackets out of 1/2 inch steel which I through bolted through the sides of the stringers, I then drilled 1/2 inch bolts through the steel and hard mounted the V Drives to the top of the steel plates, this enabled me to adjust the height with washers, the horizontial adjustment was via the brackets already on the vdrives. The plan has worked perfect, they have not moved out of alignment in 10 years...

 

Gotcha Mike- that's actually the same thing I'm doing.

However, I'm still wondering if the 3/8" aluminum I bought is strong enough to support a Chrysler 440 and Velvet drive together.....