'77 Luhrs 28 ft. diesel repower SPLASHED!

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Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

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SSSSSWWWWWWWEEEEEEEETTTTTTTTTT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[QC]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

She's going to absolutely fly now. I am guessing near 20 MPH. Weight savings and double the power, probably more than double since she couldn't reach rated RPM before. BTW, MUCH more important to have her propped/geared correctly this time around. Extended lugging will eat the gas engine.

 

[7228sedan]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Luhrs I can't wait to hear how she runs!. I have a 72 28 footer with a 330 HP 454 1.5:1 72 velvet V-Drive. The motor is a gen IV industrial block. I just overhauled the top end last year. I cruiser her as close to 3000 RPM as possible conditions permitting. I'll get from 13-15 MPH at those RPM's. With the 4bbl Quadrajet I only burn 10 gal/hr. I'd assume that I'll do around 20-23 mph @WOT but I haven't tried (no need @4.00/gallon). One question, does you boat run at it's best speed with the bow down (tabs extended)?

 

[Luhrs28]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Wayne: Thanks!

QC: I'm currently looking for a 17" X 16" or 17" X 17" prop. Last year I had a 16" X 16". I'm sort of guessing here but I think with the extra HP it'll be able to turn the bigger prop.

7228: The HP of the 6.2 diesel was so pathetic last year I really never even tried the trim tabs, other than to test them before launching. It just seemed like any position but level would've just induced drag, which I didn't have the HP to overcome.

Thanks for the continued interest guys! When I get to dropping the motor in I'll snap some more photos for you.

Bert

 

[Willyclay]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I might have to eat cat food all winter to have a high-powered gasser in my boat by April.

It's better with gravy on it. Don't ask me how I know! The new motor sounds like a great package for your classic cruiser. Good luck!

 

[QC]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I really never even tried the trim tabs, other than to test them before launching. It just seemed like any position but level would've just induced drag, which I didn't have the HP to overcome.

One thing to do at any speed with tabs. Set the throttle, and then play with the tabs. I know you don't have GPS to measure speed, but if RPM goes down = bad, if RPM goes up = good. General rule, and of course a combination that introduced ventilation would be obvious. But generally speaking this works very well, and you may be very surprised that some points with tabs down may be more efficient i.e. faster for the same throttle setting . . .

 

[YZ165]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Great job on that boat sir. I had a great time this afternoon reading and watching all the videos! Cant wait to follow along with the
continued evolution of this vessel.

 

[springer59]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

OK Bert,That just changed my mind again.Dang,I had already located 6.5 and most of what I needed to do the swap on mine.Now I have settled on going with gas 360 instead of 318.Thats a beautiful motor,if that wont do it,well, we all know it will!! Did it come with water pump ect. already on it? All I can say is WOWWWWWW!!! When do you think you can start on it?

 

[MADONN]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Burt, I have the same size and weight boat you have and I had eastern propeller work up the prop for me. My engine is a 350 chevy 315 hp and my prop is a 16x16 with a large cup. the engine W.O.T. should be set at 4400 to 4800 according to manfu. and mine is at 4400 exactly. I hope this info will help you. Also I am repowering my boat to a 6.2 and I need to purchase a heat exchanger manifolds and risors. Any info would be a big help! Thanks Mike

 

[MADONN]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Also, my speed is 25 mph. Now if thats not fast enough down the road you may want to turn the motor and put an outdrive on it then you may be looking at the 30-35 mph neighborhood at W.O.T. I have a 24 ft. boat second project I am putting my 350 in with an outdrive I'll let you know how it turns out.

 

[Luhrs28]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

QC: thanks for the suggestion on the trim tabs. That's a clever way to find out an efficient setting for them. I didn't know that. I'll definitely play around with them this year.

Springer: Yeah go gasser man! I learned the hard way. A man needs knots! To answer your question yes the Indmar engine came with everything you see in the photos. Starter, Alt, carb, raw water pump, manifolds, fuel pump, etc. I haven't touched it yet.

I'm currently studying the wiring to see what all I have to do for electrical connections. I won't drop it in until March, mostly cause I'm a total wimp about working out in the cold.

Madonn (Mike): Thanks for the info on the prop. Maybe I'll leave my 16" X 16" on then, at least til I run it a couple of weeks.

I got my manifolds for the 6.2 diesel from OSCO. I don't think anybody else still makes them. I think a heat exchanger from any 5.7 or larger gasser motor would work fine for the 6.2

 

[7228sedan]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I planned on going diesel when the time to repower comes along. The torque out put of the new 4 & 6 cyl diesels is impressive. I have a friend who repowered a 31 Bertram from twin 330HP 454's to twin 4 cyl 240HP Yanmars. Half the fuel consumption, higher top end & cruise speeds. The power to weight ratio is impressive on those motors. I couldn't justify that kind on money into my boat, but I'd look at a reman motor.

 

[QC]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Really important to understand that if horsepower goes down, the only way that speed increases is weight reduction. This assumes that the props are optimized in both cases.

 

[7228sedan]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

QC You bring up a great comment that I believe is not comprehended by most, HP vs Torque. The torque output of the little 4 cyl Yanmars was 50% higher than the big block gas motors despite the HP being lower by 110hp. In marine applications as is the same for towing applications torque is more the issue than the advertised hp numbers. Yes top end speed is the work of pure HP; however mid range cruising speed is more about higher torque at a lower RPM. The reason why most diesel upgrades require heavier shafts & struts (by the book) is the increased twisting force "torque" that the diesels put out. Luhrs's new 310 HP gas motor will probably put out similar torque numbers to the 6.2 diesel, if not a bit more as the 6.2 was naturally asperated.

 

[Friscoboater]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Very nice. I cannot wait to see how it comes out. That engine will still be pretty loud.

 

[Luhrs28]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Jay: Yes quietness was one of my goals with this swap but I'm not so sure now. I'm going to install in-line mufflers (the plastic/fiberglass type) but they don't seem to reduce the noise all that much. Oh well. Fast and loud is still better than slow and loud which is what I had to live with last summer.

Bert

 

[bear_69cuda]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Happy for ya brutha Bert!

That engine will put a smile on your face!

 

[pole position]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Best way to quiet the exhaust is to go to a single large pipe and muffler instead of 2 smaller ones.Those old Luhrs and Silvertons were pretty loud and even with new mufflers,they don't do much.

 

[MADONN]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Burt, you will be shocked how quiet your boat will be compared to the diesel. I have the 350 in mine and you can hardly here it running at an idle. It has duel fiberglass mufflers on it.

 

[7228sedan]

Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I've got the 454 in mine with 4" exhaust with the fiberglass mufflers; she's pretty loud even with the swim platform... Like you said though fast & loud is just fine!