Motor Reliablity

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Motor Reliablity

Postby Moritz » Sun Jul 17, 2016 5:27 pm

What make and who build a the most reliable motor in the 650 to 750 hp. One that will run 1000 hours with out failure

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Re: Motor Reliablity

Postby John Fenner » Sun Jul 17, 2016 5:57 pm

Two simple words,,,, Water Thunder!!!!
I never finish anyth,,,.

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Re: Motor Reliablity

Postby chuckitt@earthlink.net » Sun Jul 17, 2016 6:52 pm

If the Dyno says the engine developed 650 HP then what rpm was it turning when it showed 650 HP? If it was 7500 or more rpm then it want last 1000 hours if you keep the rpm up. Look and see what the HP is at 5200 rpm. More important is the Torque. Look for an engine that has high torque at low rpm's. Look at the torque curve of the LS376/480 Crate engine.

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Re: Motor Reliablity

Postby Olf Art » Sun Jul 17, 2016 8:32 pm

Reliability is as close as your right foot. Do you start an engine and then slam it to full throttle before it's had a chance to warm up? Do you use the best oil available and change it often? Are you more interested in WFO speed than you are about what your engine is turning at cruise? That, more than any one engine builder might have as much to do with reliability as any one other single factor. Just my thoughts. :)
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Re: Motor Reliablity

Postby Moritz » Sun Jul 17, 2016 11:57 pm

right foot is not heavy cruse 36 to 4200 change oil 25 hr and use top grade oil

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Re: Motor Reliablity

Postby CarMotorBarge » Mon Jul 18, 2016 6:16 am

So it sounds like you have a boat already. What type of hull, gearbox, and prop does it have? What motor was on the boat previously? What is your budget for the motor? What do you intend to do with the boat?
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Re: Motor Reliablity

Postby jeepinocala1111 » Mon Jul 18, 2016 6:46 am

Moritz wrote:What make and who build a the most reliable motor in the 650 to 750 hp. One that will run 1000 hours with out failure


There is a shop here in Gainesville Rollins automotive that build great engines. I have seen many 1000hp + engines come out of their shop and have never heard anyone claim anything bad about them.

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Re: Motor Reliablity

Postby SWAMPHUNTER45 » Mon Jul 18, 2016 6:51 am

What platform do you want?

LS, SBC, BBC, Cadillac, Ford, Buick, Olds ?

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Re: Motor Reliablity

Postby chuckitt@earthlink.net » Mon Jul 18, 2016 7:38 am

Cruse at 3600 rpm is like towing a camper with a half ton pickup at 55 miles per hour in second gear. Your engine want last a long time. Under a load, The LS engines will out last all the others. Why not use a higher gear ratio like a 2.38 to one or a 2.09 to one if your engine has a lot of torque. This will lower your cruse rpm's and will help your engine last longer and also save fuel.

Chuck

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Re: Motor Reliablity

Postby jeepinocala1111 » Mon Jul 18, 2016 8:11 am

chuckitt@earthlink.net wrote:Cruse at 3600 rpm is like towing a camper with a half ton pickup at 55 miles per hour in second gear. Your engine want last a long time. Under a load, The LS engines will out last all the others. Why not use a higher gear ratio like a 2.38 to one or a 2.09 to one if your engine has a lot of torque. This will lower your cruse rpm's and will help your engine last longer and also save fuel.

Chuck


Couldn't you just adjust the pitch of the prop instead of getting another gearbox?

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Re: Motor Reliablity

Postby SWAMPHUNTER45 » Mon Jul 18, 2016 9:42 am

Horsepower is good but torque is GREAT

Getting both is like finding out your wife's best friend is a Unicorn!

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Re: Motor Reliablity

Postby Deano » Mon Jul 18, 2016 10:19 am

jeepinocala1111 wrote:
chuckitt@earthlink.net wrote:Cruse at 3600 rpm is like towing a camper with a half ton pickup at 55 miles per hour in second gear. Your engine want last a long time. Under a load, The LS engines will out last all the others. Why not use a higher gear ratio like a 2.38 to one or a 2.09 to one if your engine has a lot of torque. This will lower your cruse rpm's and will help your engine last longer and also save fuel.
Chuck
Couldn't you just adjust the pitch of the prop instead of getting another gearbox?
The intrinsic problem/complication/reality with using that approach is that more pitch will generate a larger load on the engine in order to bring down the rpms, which is inadvertently going to decrease longevity over time due to the excessive loading.

The other side effect is that as you pull the rpms down, you are likely moving the used rpm range lower and getting further from the optimum torque curve in the process. This to, will decrease longevity. Ideally (predisposed prop choice aside) the most efficient gearing would have the peak torque closer to cruise rpms in order to increase longevity. Remember that the cam profile and the gearing need to match in order to optimally spin the prop where it wants to work most effectively. Changing the pitch alone, subsequently creates a mismatch between the cam and gearing, creates more load on the engine, and decreases the efficiency of the prop.

This is part of why at the referenced power levels you usually see big blocks (with more torque) using < 2.4 where generally you see small blocks using > 2.4s. I agree with Chuck's premise that for longevity, looking at torque numbers is where it's at because when torque is available one need not spin the engine up as much, which increases the justifiable expectation of it living longer and generating less grief over time.

It should be noted this is all a somewhat generic response meant to address the question about adding pitch.
In regards to the OP's current question(s), we don't know exactly what he currently has (gear and prop), or if it is his intent to use what he has or replace it. Given the wording of the original question, I would guess he is starting from scratch, although that may not be the case.
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Re: Motor Reliablity

Postby Moritz » Tue Jul 19, 2016 11:06 pm

454 punched out to 496 ruling 2.68 have run both stinger and
ox box from Dan on 8 by 16 gto hull 4 super wide blade 530 hour since new. Pitch prop for 5200 max

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Re: Motor Reliablity

Postby SWAMPHUNTER45 » Wed Jul 20, 2016 7:02 am

Sounds like a great combo!

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Re: Motor Reliablity

Postby CarMotorBarge » Wed Jul 20, 2016 7:47 am

Agreed. What is the prop pitched at? Also when you are cruising over 3600, how many people and what is in the boat? What is your complaint about the setup?
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Re: Motor Reliablity

Postby Duece » Wed Jul 20, 2016 9:50 am

I have my cruise #'s in the 33-3600 range w/just me in the boat, 14x7.5 Diamondback w/ZZ4 350/355 hp SBC. WOT is right at 5100 RPM's. I've been told that's on the mark for what my boat should do, but according to one post on here sounds like my motor won't last long. What are the cruise numbers I should be looking for?! I like the way the boat performs, which is probably the #1 consideration to take into account and I'm pretty "gentle" on my motor. That being said I really don't want to put another one on it if I can help it! :o

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Re: Motor Reliablity

Postby Moritz » Wed Jul 20, 2016 10:14 am

Prop at 2 2 people 1/2 tank of gas

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Re: Motor Reliablity

Postby Waterthunder » Wed Jul 20, 2016 10:59 am

We have a. ton of motors out there with well over a 1,000 hours. I have a few commercial ones with over 3,000 hours. The main issue is primary use and the style of boat. If you have a boat that requires 4,000 RPM's to cruise you need a big HD BBC. Most of our motors fall in the 82'' 4 blade R prop range. Our current 418's typically turn a 4 blade R at the 3rd mark around 5,400. Our Current 550HP motors a 3 blade R is not enough prop. Cages and rigging will also effect this. However if you turn a 4 blade R on the 3rd mark 5,400 and you need more than 3,300RPM's to cruise you either have a very heavy boat or a hull that is not working well. We just had a 5 SEATER 16ft Hamant go out that cruised at 2,800RPM's hauling ass no doubt that was very impressive but I cant take all the credit the hull just ran AWESOME!


Sorry got side tracked anyway the boat size and weight and cruise RPMs effect lifespan more than anything else. I also cut off a few hundred hours if you run a 2to1 ratio. 2.38 is better and 2.68 is the easiest on the motor.
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Re: Motor Reliablity

Postby CarMotorBarge » Wed Jul 20, 2016 12:11 pm

Moritz wrote:Prop at 2 2 people 1/2 tank of gas


Lowering Max RPM by putting more pitch in the prop will lower cruise RPMs. So you have a GTO hull. Is there a poly wedge in the back between the hull and the poly? GTO does this to eliminate porpoising, but it puts the boat on its nose. The boat riding on its nose will cause higher cruise RPMs.
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Re: Motor Reliablity

Postby jeepinocala1111 » Wed Jul 20, 2016 12:20 pm

CarMotorBarge wrote:
Moritz wrote:Prop at 2 2 people 1/2 tank of gas


Lowering Max RPM by putting more pitch in the prop will lower cruise RPMs. So you have a GTO hull. Is there a poly wedge in the back between the hull and the poly? GTO does this to eliminate porpoising, but it puts the boat on its nose. The boat riding on its nose will cause higher cruise RPMs.


I have seen that wedge without it putting the nose down like you are saying.

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Re: Motor Reliablity

Postby CarMotorBarge » Wed Jul 20, 2016 12:30 pm

jeepinocala1111 wrote:
CarMotorBarge wrote:
Moritz wrote:Prop at 2 2 people 1/2 tank of gas


Lowering Max RPM by putting more pitch in the prop will lower cruise RPMs. So you have a GTO hull. Is there a poly wedge in the back between the hull and the poly? GTO does this to eliminate porpoising, but it puts the boat on its nose. The boat riding on its nose will cause higher cruise RPMs.


I have seen that wedge without it putting the nose down like you are saying.


We need to do an experiment. Are you willing to put the poly wedge on your current boat and report to everybody how it affected your cruise RPMs and max speed?
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.88 Ox Box swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer

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Re: Motor Reliablity

Postby 462kwells » Wed Jul 20, 2016 12:32 pm

No doubt there are a lot of good engine builders out there, however Dave at WaterThunder applies his knowledge to Airboat engines I believe he must live inside an engine block because he knows what hurts and what helps and engine, just can't beat hard testing and experience

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Re: Motor Reliablity

Postby Moritz » Wed Jul 20, 2016 4:01 pm

I have the wed installed and the boat will porous with just two people but not 4

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Re: Motor Reliablity

Postby Olf Art » Wed Jul 20, 2016 7:55 pm

The Ford Motor Company built the B-24 Liberator bombers ( yes they did, at the Willow Run plant) before the start of WWII. The engines were Wright Cyclones that could operate at 2.600 rpm. cruise for hours at a time over the Pacific Basin, with more range and bomb load ability than anything else in our inventory at the time.

Turning a prop isn't about horsepower or rpm. It's all about torque and reliability.
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Re: Motor Reliablity

Postby OneBFC » Wed Jul 20, 2016 9:32 pm

This has been beat to death so many times. I sure hope I don't regret posting what I'm about to say. There are MANY simplifications taken for granted here, please don’t beat this up on semantics, OK? Also, not trying to “start” anything here. If you think I am wrong, please show me. If you want to just say “you’re wrong” and not back it up, you are only going to embarrass yourself. IF I am wrong and you can prove it, I’ll be the first to admit my error and concede to your superior mind :)

Turning a prop isn't about horsepower or rpm. It's all about torque


The above quoted statement is, unfortunately, wrong. It's easy to fall into this line of thinking too, so quite understandable. In the spirit of truly understanding however, here's the real answer to "what matters" when it comes to "Turning a prop".

Any given propeller will require a certain amount of propeller shaft Torque in order to spin at a given RPM. For a hypothetical example, Propeller "A" is designed to require 600 lb-ft of Torque in order to turn 3000 RPM. Intuitively, this same propeller requires less torque to turn 1000 RPM. I don't think anyone will argue that point.

Now, if you have an engine that you want to use with Propeller A and you want the propeller to turn 3000 RPM, you will need the engine to produce 600 lb-ft of torque, at the prop shaft, when the propeller shaft is turning 3000 RPM. This is most likely pretty obvious still and I can hear the "no sh*t..." from here even before you think it :)

Now, let's say you have two engines to choose from to use. Engine #1 produces 600 lb-ft of torque at a convenient 3000 RPM. Engine #2 produces 300 lb-ft of torque at a lofty 6000 RPM.

Which one can turn Propeller A 3000 RPM?

Clearly, Engine #1 can. No argument there, it’s obvious! What about Engine #2? Well, since it produces only half the torque that is needed at two times the RPM desired, it won’t turn the propeller 3000 RPM unless you use something to reduce the speed of the engine. Commonly people use Gear boxes, belt drives, etc to do this. Of course this is more “No Sh*t”, just hang in there.

Engine #2 combined with a 2:1 reduction will produce 2 X 300 lb-ft = 600 lb-ft of prop shaft torque at 6000 RPM / 2 = 3000 RPM. So, Engine #2 also can turn Propeller A 3000 RPM with this additional propeller speed reduction device (also known as PSRU).

All of this is likely well known and understood by everyone here, but….reading posts like the one quoted above that I post here again makes me wonder,

Turning a prop isn't about horsepower or rpm. It's all about torque


Clearly this can’t be a true statement, right? Is it not obvious?

Engine #1 produces 600 lb-ft of torque at 3000 RPM. This means it is making approximately 343 hp. The mathematical formula used here to determine this is:

Torque = (5252 X hp) / RPM


Engine #2 produces 300 lb-ft of torque at 6000 RPM. This means it is making approximately 343 hp.

Wait, that is exactly the same hp for each engine!

The reason for this is that in “reality”, hp (Horsepower) is what does “work”. Without “work” nothing happens. Just put a case of beer at a job site at 9AM sometime and see how much “work” gets done :) I joke...sorry.

Anyway, so Torque by itself actually means NOTHING. It is not what matters and in fact Turning a prop is all about Horsepower….

Last example to make it indisputable….

Engine #3 produces 1200 lb-ft of torque at 1500 RPM (hey, that's 343 hp!)
Engine #4 produces 150 lb-ft of torque at 12000 RPM (343 hp here too!)

Will either of these engines turn the propeller 3000 RPM?

Engine #3 will...IF you use a device to double the propeller shaft speed….use a 0.5:1 gear box or belt drive to do this and the propeller will then have half the torque, so 1200/2 = 600 lb-ft and double the RPM, 1500 x 2 = 3000 RPM. Voila! Just what the propeller needs to turn it’s magic 3000 RPM….

Engine #4 will….IF you use a 4:1 reduction drive to multiple the torque by 4 and divide the engine speed by 4….you can do the math here.

So, hopefully, this pretty clearly demonstrates that Horsepower is definitely what matters and NOT torque. An engine could produce 1 lb-ft of torque and as long as it could turn enough RPM and still maintain that same 1 lb-ft of torque, you could spin Propeller A with it.

Horsepower is simply a measure of Torque at a given RPM

ALL of this aside, when talking about longevity, low RPM, high Torque engines/motors are very good choices. If you can achieve the required propeller shaft torque with an engine at low RPM with no propeller shaft speed reduction or increasing devices (gear boxes), even better. This is really how people get stuck on direct drive engines. They are less complex and can be very reliable due to their low operating speeds as compared to other higher operating speed choices that do require propeller shaft speed changes.

The gotcha is, low RPM engines are difficult to make and still produce a lot of Horsepower without the engine weight becoming prohibitive.

Here’s some calculation I played around with in the past in a spreadsheet. It’s got some questionable propeller ideas in it that I had at the time, but the engine calculations are spot on. Feel free to make a copy and poke around with it. I made this crude spreadsheet when I was building the boat in my signature.

https://docs.google.com/spreadsheets/d/18zKUR8Vktr0bDQn8GpMpJZP8oANNzUDQhQKNPBAil9w/edit?usp=sharing

Hopefully I get to build a few more boats in the near future.

Good luck with your project!
-Russ
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