'77 Luhrs 28 ft. diesel repower SPLASHED!

chriscraft254

Commander
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Jun 4, 2011
Messages
2,445
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Hey man, just read this thread all the way through. You did a good job getting that old beast on the water again. It amazes me how many people here didn't warn you that deisel wasn't going to push that heavy right! And the ones that say its fast enough obviously haven't had to outrun a storm in heavy seas. You need more HP, plain and simple.

To give you an idea of the 350 gasser performance, I am running a 350 with a 325 hp rating. My boat length is at 26'8" with out the bow pulpit or stern platform. It weighs in fully loaded with a couple people on board at about 8000 lbs. I see 42 to 43 mph tops. Of coarse mine is an I/O which is going to see more speed anyway. My point is, for your hull, (imo) you need to go back to the 360 or even better a 454. Yes you might have to change transmissions etc for the 454, but might be worth it in the end. Yes,it will burn more fuel than the 350 but not much because your boat would make that 350 or 360 work much harder than the 454 would. I don't think a 260 hp 350 gasser is going to gain you much. If you do go the 350 route, get a high HP motor. May cost you a bit more up front, but the extra Hp is needed here.


Like others have said though, re-proping and getting those rpms up will definately help with what you have. I wouldn't do that without mufflering that motor though. That thing is LOUD! Good luck with whatever you decide to do.;) Budd
 

Willyclay

Captain
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Sep 8, 2006
Messages
3,264
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

By the way I'm secretly lusting after a '79 Bertram 31 that's for sale in my marina. It has twin Cummins diesel V8's! They want $55K for it though, which is more than a little out of my price range.

They will take less for it!
 

Luhrs28

Chief Petty Officer
Joined
Jul 14, 2010
Messages
423
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

QC: Thanks for the cool graphs and well thought-out reasoning.

Let the arguing stop. The die has been cast: I'm going gasser. I was down at my boatyard today talking with their Mercruiser guru about the 5.7 and a question came up:

Should I go 2 barrel or 4 barrel carb? (and please don't tell me I should buy a fuel-injected engine. I like carbs. They're simple and I know how to fix them. About the first 15 cars I owned had carburetors)

I was going to post this question in the Mercruiser section but I know the mods like everything to stay in 1 thread.

Thanks guys, and I wish everyone a nice Sunday.

Bert
 

QC

Supreme Mariner
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Mar 22, 2005
Messages
22,783
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Sorry Bert, I guess it is still analogous, but sorry this is monopolizing your thread right now. Maybe this will help . . .

This is a horsepower, fuel and torque chart from a little 150 bhp Cummins marine engine. It compares a Propeller Load Curve, the power required, vs. what is available. The relatively straight lines on the bottom of each is what the prop requires, the curvy line above is what is available in hp, torque and then the associated fuel. Oh, oh, you can double or triple every number on the chart and be able to consider a 300 or 450 hp example. The differences are not even rounding errors in regards to this discussion.

attachment.php


This illustration is essentially the same for gasoline and diesel except the max available curves at low RPM are not as far apart. Yes, less torque. But here's the whole flippin' point. How are you going to use that additional available power? Upshift? No, can't do that. Go climb a hill? Well I guess there are lots of little ones that we call waves, but there is no place on the water to sustain a "lug" that would allow you to utilize that extra, reserve power. Just a reminder, we are talking boats here. One gear, and no hills.

The bottom lines leave out one thing, the higher load at the point of getting the boat up on plane, and of course that is different for every hull and why it is excluded. Regardless, I assert in the case of a displacement hull that does not come into play at all, and in the case of a semi-displacement hull (Bert's) it is minimal. So if the propeller only needs X amount to go, and the engine has more power than that is required (say at 2000 RPM) what do we get if we have more torque there? One thing . . . better acceleration. Has Bert mentioned acceleration as his concern? If I missed it sorry, but what I think he wants is more speed and less noise. For me that says turbocharger (natural muffler) or, has Bert has determined, a regular, smaller, lighter, every day, conservatively rated small block with twice as much power as he has now ;) Great choice.

I was going to post this question in the Mercruiser section but I know the mods like everything to stay in 1 thread.
I wouldn't say that, our deal is more one thread per topic. This is a different topic than your original restoration. I think you should put it non-repair I/O and IB.
 

QC

Supreme Mariner
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Mar 22, 2005
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22,783
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I moved most of the torque v.s horsepower deal here: http://forums.iboats.com/showthread.php?t=522746

Wasn't fair to Bert, but deserves further understanding. Left the graph stuff above as it may be helpful. Sorry for any disconnects in the discussion. I wasn't sure how to fix the continuity in either, but tried anyway . . .
 

g1sammons

Seaman Apprentice
Joined
Sep 3, 2011
Messages
44
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Question Bert
When you switch to the diesel was there also gear ratio change or prop change
ornr u tuning all the gear that came off the 360.
?
 

Luhrs28

Chief Petty Officer
Joined
Jul 14, 2010
Messages
423
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

G1sammons: I had to change everything 'cause the tranny that came with the boat was blown beyond repair also. (plus the V-drive case was cracked from ice in the jacket) So I bought a used Paragon transmission and 1.5:1 ratio V-drive. I think the original V-drive was also 1.5 but I'm not 100% sure of that.

I also changed the prop to a 16" x 16". I still have the original prop...............I think it was a 16" x 15".

By the way the tranny worked perfectly all summer. I'm very happy with it.
 

g1sammons

Seaman Apprentice
Joined
Sep 3, 2011
Messages
44
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

If you going to use a carb would only consider. 4 bbl
Thou I would try to steer you to fuel injection
You don't need to buy a fuel injected eng rather there are several aftermarket bolt on that dont cost much more than a new carb
Holley make some nice stuff and they are simple to work on
Why ? Much more efficient and less problems in the long run
You will run better longer and save fuel in the process
You can find them around most performance stuff

Are you going to build or buy a engine?
 

sdowney717

Petty Officer 1st Class
Joined
Jul 16, 2011
Messages
225
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I would use a quadrajet.
Mainly because I know them well.
They are easy enough to tune. the hardest thing is putting the primary rods back into the jets which I use a strong light to see in there.

http://www.corvette-restoration.com/resources/technical_papers/Q-Jet_Carb_Tuning.pdf

The M4M and 4MV series are different, M4M take larger jets and rods. M4M jet to 75 and primary rod 50 and drill out the idle tubes and it works well.
One advantage of a quad is the small primaries and variable jet size with the rod dont waste fuel as when your idlle around or go slow but open up big when you need it to. I remember my brother's 4 barrel double pumper Holley's were always leaking fuel and serious gas hogs. Todays fuel also wants to ruin rubber gaskets and seals, the quadrajets have small float bowls and no rubber seals gaskets that can fail and leak the fuel out of the float bowl.

I set up some of these and here are a lot of links to look threw.
http://www.binderplanet.com/forums/archive/index.php?t-98160.html
 

parrisw

Ensign
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Jun 8, 2009
Messages
985
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I've never had a problem sealing up a Holley, you just need to use the right gaskets, its not rocket surgery.
 

sdowney717

Petty Officer 1st Class
Joined
Jul 16, 2011
Messages
225
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I am not the only one to notice todays gas eating up the holley parts.
I have also read on the Binder planet that the Holley power valve is not E10 compatible.

Just a quick look brings up this thread about the Holley leaking out on the intake manifold which brings back bad memories to me
http://www.dfwstangs.net/forums/showthread.php?p=6383625

http://www.binderplanet.com/forums/showthread.php?t=103689&highlight=power+valve+ethanol
http://www.binderplanet.com/forums/showthread.php?t=101353&highlight=power+valve+ethanol
 

g1sammons

Seaman Apprentice
Joined
Sep 3, 2011
Messages
44
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Hmmm
Have run them for years never herd of that but then we've always run race fuel
 

Alwhite00

Master Chief Petty Officer
Joined
Apr 14, 2011
Messages
885
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

Nice project, Keep it up.

LK
 

QC

Supreme Mariner
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Mar 22, 2005
Messages
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Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

That is cool.

I will say one thing, and this is simply math. There is no way that a heavier pair (the Volvos) with a lower advertised hp "rating" (225 vs. 245) is faster. One of their ratings is either conservative or aggressive, or they are not setup right.
 

Luhrs28

Chief Petty Officer
Joined
Jul 14, 2010
Messages
423
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

I was just talking with the engine guy at my boatworks, who's been checking with Mercruiser and some other suppliers. I really just wanted a plain-jane 5.7 with 250HP. Do you know what their minimum HP is with a new 5.7 nowadays? 310HP!!!!

They also have 383 strokers with 340HP. Yowwwiiieee!

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

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

A new engine from anyone will require Catalytic converters too. And I assume all are EFI, so not sure those fit your requirements. You need to be working with a rebuilder IMHO. Or buying something used.
 

Luhrs28

Chief Petty Officer
Joined
Jul 14, 2010
Messages
423
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

QC: I could swear my supplier said carbed, but I'll check again. I'll also ask him if cats are required.

And yes I'm also checking around for a rebuilt engine. Lots of guys have long blocks fairly cheap but I really don't want to have to forage around for every little bracket and pulley to make it a complete engine.

Thanks as always for your input.

Bert
 

parrisw

Ensign
Joined
Jun 8, 2009
Messages
985
Re: '77 Luhrs 28 ft. diesel repower SPLASHED!

That is cool.

I will say one thing, and this is simply math. There is no way that a heavier pair (the Volvos) with a lower advertised hp "rating" (225 vs. 245) is faster. One of their ratings is either conservative or aggressive, or they are not setup right.

ha ha ha, still can't let it go eh? They said the diesel was faster!! case closed! LOL
 
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