Insight in diesel Luhrs 28 re-power

MIA thanks for the info! Yes, I'm not going to change the shaft log but will put in a new shaft because I have no idea of the alloy of the old one and at 1-1/4" it will have to be the newest 22 grade to be able to apply 300 hp to it. The old engine stringers were 4x6's covered in roving, bolted to the 2x6 hull stringers (also glassed) they ran the length of the engine bay also providing a base (with wedges) for the V-drive. I'll do the same as they are at what seems to be a universal spacing apart for engine mounts, the height I'll probably work out with mockups just to be sure once I commit to an engine. Same with the shaft as I'll mock that up and then have it machined. The 17" four blade prop that was stock had only about 1.75" clearance to hull, a bit tight. So that's were that RPM variable fits in as higher cruising RPM allows smaller wheel. Ultimately, seems shaft dia. and shaft log angle are really driving engine choice. If I start over with a new log and strut It would allow much more options but not interested in opening up that can of worms.
7228Sedan, yes, it's weird I found some old Luhrs promo material that mentions in the early 70's you could get the boat in traditional wood topside construction or all fiberglass, guess it was a cost option. I love this boats low wide and simple design, (and the 3GPH I got, albeit at tugboat speeds) but if I knew how much rot I had when I started this project I would of hauled it to the dump. But hey, I have learned a lot and found it's a really juicy rationalization to buy more tools! I'm lucky that it's parked in front of my shop so basically the biggest cost so far has been time, and I've got that. In the end, I'm replacing almost everything and it will be way stronger and more durable than the original. The original Honduran mahogany T&G cabin sides are now 1" thick laminated marine ply w/4 coats of laminating epoxy and 4 of LPE on the interior mahogany finish 4 coats 2part epoxy/ LPE on the exterior. The sides where challenging as they are 14' long, requiring me to do some 8:1 scarfs on the 1" thick laminated 4'x8' sheets. Lots of time to build the bench and jigs to support it all. I'm keeping all the original cabin lines and it's been a challenge seeing as all the decks are curved and the cabin sides angled, lot's of mockups! Always interesting tearing into old carpentry and finding all sorts of boo boo's - Friday afternoon rushed construction details. I'm replacing all the wiring (which was non marine grade) plumbing and tanks. Tore out what is probably several owners worth of sub grade hack jobs. Thank god the hull is built like a tank! The Mercury Diesel options are a 2.0L four and a 3.0L V six that are VW TDI diesels and a 6.7L inline six (480-550hp) that is made by FPT, a Fiat subsidiary that my local diesel Cummins/Yanmar supply now carries and has good things to say about, he can get me a new FPT 280hp one for @30K. Funny thing with the Mercury line is that the dealers seem to know less than I do when it comes to the diesel line. And the price quotes I've been getting range wildly 28-50K for the 3.0L Some are also kinda leery about Mercery diesel as apparently they have changed suppliers a lot (Navistar was one) causing local mechanical support/training issues. Thanks for all your input! One of these days I'll sit down and organize an online site with all the photo's I've shot documenting the whole process.

 

I'm excited to follow along, I miss mine a lot... it no longer suited the family's need as I am looking to do some extended cruising/offshore fishing. Plus, I couldn't safely get my disabled son up the ladder to the bridge. Aside from the future dreams, she was perfect. A very efficient, stable ride. MIA, I'll be lurking in the depths, not going anywhere anytime soon Cheers all.

 

She's a beauty, I like the dark blue hull, is that original? If you don't mind, curious what you got for her. It is in the back of my head deciding on the re-power. I paid 25K 30 years ago for my diesel version. I don't expect to get back my labor cost for the cabin/decks rebuild, but would like to recoup the engine cost. Thanks!

 

Thank you, definitely a labor of love as you are well aware of . Originally she was same as yours with off white and powder blue stripe. I painted the hull, deck, and fly bridge myself using Interlux Perfection. Hull side is Mauritius Blue. Deck, bridge were bright white. I put down Interdeck in white in the cockpit. Here's some more pics from my listing when I let her go. I think I got around $7,500-$8000. With all of the sweat equity, and fresh motor, transmission, prop, shaft, electronic upgrades, rewiring, updated shore power AC/DC systems etc I certainly didn't make any money that's for sure. But that's not what this was about. I had her for 10 years, and turned her form a decrepit old scow into something relatively respectable. I learned a ton, and discovered all of these fine folks in this forum along the way. There are multiple lifetimes of experience from around the world in here. All of which came into the picture at one point or another. Please shoot me a message at any time if you'd like to chat. Sorry, didn't mean to hijack your thread ;-)

 

Quite late to the party, obviously, but wanted to put in my half-cents worth.
When my grandfather bought his '73 Luhrs Super 360 it had a pair of 185hp Perkins diesels in it. It was tough keeping her up on plane; one engine or the other would overheat. Despite all kinds of maintenance activity, those engines would not keep her up without overheating. So he repowered her with a pair of re-built 225hp(?) Cummins 6BTs. A great difference in performance!
My recommendation, if you haven't already done so, is to go ahead and install a diesel engine on yours. An added benefit is that fuel consumption is about half that compared to a comparable gasoline powered boat, plus less maintenance/parts to fail.
One thing to consider - install a larger hp engine than you think you need. Why do I say this? They built boats heavier than expected/estimated back then. I found out from a potential buyer that while my Luhrs 360 was estimated to 15,000 pounds, she weighed in closer to 21,000 pounds. A huge difference! But those Cummins 6BTs don't seem to be phased.

 

ELCADA, welcome to the forum I actually looked into repowering my 280 with a single 6BT for just that reason. The biggest factor aside from the associated costs, was the motor's height. I had to raise my deck with additional support to properly clear the 454. The Cummins was a few inches taller overall when compared to the 454. It would have been a much larger effort to maintain the flush deck. That being said, a fresh big block, worked prop and the trim tabs made her run like a runabout. Would hold plane at 10-11 knots with the tabs extended and a respectable top end just shy of 30mph. Cheers!

 

Been a couple of years but I thought I’d post an update for anyone interested. Took a year or so off for other priorities. I finally finished the cabin rebuild and got a finish coat on and installed the new side windows. I’ve ordered new front and aft windows as well to match. Quite a journey for me, learned a lot about woodworking on a boat, everything is curved or angled in that cabin, lots of templates to make all those cabin sides! Got pretty good at fabricating stepped plywood patches for the roof and deck rot damage. Built an 8:1 scarfing jig that got a lot of use repairing beams and fabricating 1” thick 14’ plywood panels for the cabin sides. Everything is coated with 4 coats inside and out of laminating epoxy and 4 coats of LPE with hardener. Made a few improvements to the design increasing the width of the roof side caps to keep water from creating black streaks down the cabin sides and added a groove underneath to accommodate an RGBW LED strip creating indirect lighting on the decks. Deck cabin joints are not just screwed and calked with a 1/4 round on the seam. Now everything is screwed with epoxy fillets with glass tape fitting into a shallow groove so everything is flush. Currently the aft is a clean slate, empty, no back cabin wall, no cockpit deck, no engine, trans, V-drive, wire, plumbing or tanks. It’s all going to be new. Looks like a Yanmar 8LV 320 will be the power plant. I’ll have to upgrade the shaft to 1 3/8” but can keep the current log and strut. The deck may need to be up an inch or two but I’m building a new deck anyway! Currently have Yanmar data models to place engine choices into a 3D hull that I’m creating to check any interference issues Still a long way to go, but the fussy curvey angled stuff is mostly over. Definitely a labor of love, looking back on the hundreds of photos I’ve taken of all the repairs, I’d never start If I knew what was ahead. I’m lucky it’s located just outside my shop and I can pick away at it. In the end, I’ll have a boat that I’ll know every square inch of. My wife has been helping and she has a great perspective of the whole project when people look cynical about it all. We’re basically building a cheap vacation cabin. Even with the engine cost, it’s cheaper than most motorhomes and way cheaper than any cabin we could afford, and it’s waterfront!

 

It's so nice to see the occasional follow-up when folks like you Luh28 ressurect these old girls. You might know that back almost 20 years ago I restored a 1973 Silverton 25.5 "Sportster". That's what they called her. Built by Silverton/Luhrs down in NJ. I knew when I bought her that she wouldn't plane. But she had a broken motor mount and the engine stringers were shot. I assumed once I addressed those issues that she'd be OK. Well, you know what they say about assuming, right?

Years later, we launched her and guess what? Still wouldn't come up on plane. Not even close. Just churned a lot of water and went nowhere. I don't mind traveling a 6 to 8 knots but I had this beautifully restored boat what just wouldn't move. So I started asking questions. Read Dave Gerr's "The Propeller Handbook". Called Michigan Wheel. Called Walter Gear. Called Olympic Propeller. Called Bennett Marine.
Walter Gear made the funniest observation. "Geez" they said. "We don't even keep records back that far but based on the serial number of the V-drive, it seems like it's original to the boat. But we can't figure out why they installed a 1.5:1 drive. That's a ski boat drive ratio. You have a cruiser. It's never going to work."

My boat was, and still is powered by a 302 Ford V8, rated at 220 HP.

A lot of calculations using Dave Gerr's formulas led me to change the propeller. But that also required a new V-drive as the gear ratio needed to spin the new prop was 2.05:1. Walter doesn't make my old gear box anymore. The new one is a little longer. The engine needed to go back about an inch and a half. But nothings simple on a boat. Going back also meant going down a bit. It worked but it was close. And it took a lot of time.

Here's a photo of the original prop next to the new Michigan Wheel DQ 486 that was needed. Notice the difference in the blade area. I learned this from Gerr's book. There's a lot more to prop selection than diameter and pitch.

After the new drive was installed and the prop was on it was time for some testing. I'm down at the lower helm and a friend of mine, who's a retired ASE master mechanic is watching from the rear cockpit. She still wouldn't get out of the hole! But he made another great comment I'll never forget. With the old prop I could spin the engine right up and past 4400 RPM. With this new prop the engine wouldn't rev past about 3200. "You should see this" He said. "It's not going to plane but you're pushing a mountain of water out of the back here! It's a huge difference."

Trim tabs were the final solution. 24x12's. That did the trick. Cruising speed about 15 knot's and top speed of 24 or so.

Don't assume anything. I'm just taking a little time to write this as a cautionary take. Sounds like you haven't done anything yet regarding the driveline. I learned that just because the boat was built in a factory, it doesn't mean that they made the right decisions. They clearly didn't. Do a lot of homework. Get it right the first time. I made a lot of extra work for myself by assuming that the boat was right from the factory and that fixing the motor mounts and stringers would solve the problem. Big mistake.

You might find this interesting. Click the link, then scroll to page 77.

Boating https://books.google.ca/books?id=yW-2GoXscmgC&pg=RA5-PA81&lpg=RA5-PA81&dq=boating+magazine+test+26+silverton&source=bl&ots=v-eRWRJ-pg&sig=ACfU3U3Me6tnlALBFbiMkoGtEf2qoaTadg&hl=en&sa=X&ved=2ahUKEwj4sbjEv6LnAhXOvJ4KHc_2DnwQ6AEwCXoECA0QAQ#v=onepage&q=boating%20magazine%20test%2026%20silverton&f=false

Here's my 52 year old Silverton today.

As you know these projects are a marathon, not a sprint. Keep going! Pace yourself.
Regards,
MIA

 

Nice to hear that the project is still moving along. You have me REALLY craving another myself... keep up the fantastic work, and the updates here!

 

MIA your experience with your prop sounds familiar. When I got the boat it would top out around 10 knots, (even with only the 120HP diesel Perkins) then a blade on the prop broke off due to corrosion (of course when it was blowing 20+ knots) The boat came with a spare and had it put on. Never got it over nine after that. Boat has tabs but they don't seem to help. Couple of years ago I found the old prop and compared it to the newer one and although same pitch and diameter, the old one had more surface area. Live and learn.
I scanned my hull in 3D and placed the Yanmar engine models into it for fitment. The 4LV 250 fits fine, (verified with actual measurements) the 8LV 320 just barely. For only 4K more I think I'm going to go for the 320 and have the headroom available. The 320 V8 is a the lowest of the 3 V8 power levels so not working as hard and runs at same 3800 RPM as 250 I4, it's also a Toyota. I'll probably raise the cockpit an inch or so.
Question: Originally the engine stringers were painted 4x4's bolted to the glassed 1 .75"x 5.5" stringers and sitting on the hull. They were rotted, and I tore them out. The engine suppliers are saying to not replace the 4x4's but to rebuild the glassed stringers and that they will bolt aluminum angle brackets to them to support the engine mounts. This because they say it allows more clearance around the base of the engine. Thoughts? see pics below of old mounts (the raised unused section was for the gas V8 option) you can see were the mounts were for the Perkins 6-354 I had. Best V drive gear for my 15 degree shaft seems to be the ZF 48IV, it's a lower profile and doesn't tilt the engine aft as the 12 degree v drives do.
Thanks for the support!

 

I would agree 100% with your engine installer. Paul Ricelli, who was a major contributor to this site (passed away in 2018) gave me some tips when I replaced my engine stringers.

I used a long Sawsall blade and bent it slightly to align with the angle of the hull. Drilled a hole in the stringer so I could get the blade in there. I was able to run the Sawszall along the inside of the hull and cut out the stringer. I'd suggest making a jig that straddles the existing stringers so that you can install the new ones in the same position as the old ones.

Make sure you understand how to make a nice radius where the stringer meets the hull and the floors or transverse bulkheads.

Believe it or not I used Owens Corning Foamular 250 (yep, right out of Home Depot) as the core material for the stringers. Placed wooden blocks, thoroughly epoxied, into the foam cores where the aluminum angle and backing plates for the engine beds are located. Some people can't get their head around this fact. A stringer core adds no strength at all to the structure. All of the loads are carried by the fiberglass that is draped over the core.

It's a messy job, but I donned a Tyvek suit and installed the new stringers using 1708 biaxle mat and epoxy. I laid up 5 layers of the 1708 and a couple of extra layers where the beds are located. I'm told that I may have overbuilt them but it's been about 17 years since they were installed and I've had absolutely no issues.

I have some pictures that are on an old laptop, if I can find them I'll post them for you.

BTW, you might want to consider replacing that cable steering while you have an empty space back there. Nothing lasts forever!

Have fun with it!

MIA

 

Thanks! Yes, Ill stick with their advise, also, because the V drive is 20º and my shaft is 15º the engine is tilted 5º at dock but will level off under way. Brackets will be easier to fit given the engine angles, (see above rendering) Think I'll just laminate them up to be thicker after cutting out all the rotten wood. Lots of epoxy fillets for fiberglass corner radius.