|08-31-2012 08:13 AM|
From Sunday... we had more pulling power than we had barefooters, but here's a 5-man attempt.
|08-31-2012 07:32 AM|
OK, time to bring this thread full circle...
After mulling it over, this spring we decided to bite the bullet and go with a custom RH roller cam. We freshened up the heads as well, with new Ferrea valves (SS intake, their version of inconel on the exhaust). Cam specs are on the order of .604, both I/E. With our high-ish (cam builder came up with ~10.4:1) compression, he erred on the side of a larger cam, in hopes that the longer duration would keep cylinder pressures down. Something to consider on a marine engine that is always under load, he explained (this guy does solely marine engines). HP is estimated to be in the ~480hp range.
Got it all buttoned back up last week with new custom Manton pushrods, and it we did final assembly this weekend. We still need to play with props a bit (we're not hooking up great with the 3-blade 13x14), but it pulls strong all the way to 5700rpm and just over 62mph on the GPS (best of 62.8mph thus far). It pulls a decent number of guys out of the water pretty strong too- so it will serve its purpose. Feeling pretty good about having it back in the water at this point!
|03-05-2012 09:03 AM|
|airboat||Never-mind, re-read the whole post,|
|03-04-2012 09:01 PM|
Yeah, that's what I was thinking but had to check. and my I thought you could change the pump direction. http://www.velvetdrive.com/techinfo/V7172/V7172pg1.pdf
why don't you want to change the direction of your motor? Drivers seat on mine is on the right hand side.. Perhaps not ultimate but I don't think it's really noticeable.
|03-04-2012 08:52 PM|
No need to pull the numbers off the Velvet- all of them can be spun in either direction. You just need to index the pump correctly. Yours spins LH because its bolted up to a LH engine. Mine spins RH because its bolted to a RH engine. What it cant do is change the direction of rotation... so the prop rotation (which I am keeping RH) needs to match the engine rotation... thus, the RH engine.
58mph out of a ski boat is serious. HP is only part of the picture though- a fast hull will make up for lack of hp. I know of a 17' wooden inboard produced in the early 60's with a stepped hull that would run in the mid 50's with a stock 210hp y-block.
|03-04-2012 08:41 PM|
I have a Velvet drive on mine and it's standard rotation. I could get a number once the snow melts off the cover.
I put a Comp XS268s solid flat tappet in mine because It was laying around, At the same time I bolted a set of L29 Vortec heads on the stock bottom end after rings and bearings, some roller rockers and a performer intake.
I never did like the angle the carb sat at so I bought an angle spacer or tilt shim that Glen L sells, http://www.boatdesigns.com/Tilt-Shim...ctinfo/90-410/
While apart I also wondered how you could get the oil to the dipstick full line without the crank running in oil all the time, after confirming it wasn't possible I built a larger sump , kicked out and level with the bottom of the boat.
All I can say is WOW and no issues getting to 58 mph... My Eliminator might be a little lighter than your boat but not by much. It's amazing.. Love it! and not as nice an engine as yours.
|01-27-2012 03:54 PM|
Ok man I see what ur saying,the BW is what we call a Coaxial transmission rather than a drop down where the output is below the centerline of the crank by about 4 inches or so.
The damper you have in your BW trans,we call that a torsional coupling,on bigger transmissions it is either rubber or silicone.
But you probly dont need all this info,anyway good luck with your boat.
Its a nice one!
Most people dont realize just how much horsepower it takes to push a boat to 50MPH a 72 footer with a pair of 2000 series MTU engines is about 45 MPH at WOT at about 160 gallons an hour total fuel consumption.
ZF Marine bought my company out in 2000 n im long gone from there.
I still however work on go fast boats with big Diesels.
|01-27-2012 09:08 AM|
You can switch the direction of rotation on the velvet drives by indexing the pump. But you cant spin them full power in reverse. EI, the rotation of the engine (in fwd) has to match the direction of rotation of the prop. To turn a RH prop (required for proper performance with this hull), you need to turn a RH engine (with a BW), or find a trans that switches the direction of rotation (like a ZF Hurth or a PCM 1.23:1), allowing you to use a LH (standard rotation) motor.
Im not familar with your terminology (spring torsional coupling, centa, vulkan), but the transmission mates to the engine with a spring loaded damper plate, which we replaced with new last year. We do not use any dampers between the output coupling of the transmission and the driveshaft- these are not required on boats this size. When used in this application, its oftentimes a bandaid to cure the symptoms of a bad engine/trans damper or misaligned powertrain.
|01-27-2012 08:52 AM|
Ok well the 72c is a good trans. I see your point,you would defenetly have to shorten the shaft
Ive seen them behind 6V53 Detroits n they hold up.
Ok on sticking with what youve got,have you checked to see if you can change the BWs input rotation by just moving the thrust washers from front to rear or vice-versa,I know on big trans thats what we do.
Just for curiosity.Do u run the the spring torsional coupling on the 72C or a centa or vulkan?
|01-27-2012 07:06 AM|
|johnnyg||This guy knows 50 MPH on water is fast!!|
|01-27-2012 07:03 AM|
Thanks for the response.
Im familiar with ZF's being able to turn both ways under full power. For a future project, I may consider building a LH engine in front of such a tranny.
For this one, the motor is done, with all of the RH components already in place (save for the cam). They arent necessarily hard to find (if you know where to look), and with the exception of the cam, no more expensive. Ive heard good things about the ZF, but the BW 72c is tried and true, especially in front of a big block.
To swap the rotation of this engine, Id be looking at a new timing set, starter, rear main seal, and transmission. Im also unsure of the ZF's length- we may need to pull our shaft and adjust the length too, if we swapped out the BW. All those items would cost well beyond the ~$500 premium for the RH roller cam (as compared to a regular LH roller)... not to mention, a lot more work. I think we'll stick with a righty for this project.
Just gotta make a decision on the cam!
|01-27-2012 06:52 AM|
Hey, I dont work on small boats,only big Diesels Vikings,Bertrams etc.
Why dont you go to SAE rotation n get rid of the Borg Warner n put a ZF trans in there you can run RH input rotation into these,of course the prop would have to be changed but I think most of ur problems trying to find parts will go away then.
Call ZF n find out if a trans is available for your app.
Im almost sure it is.
All modern twin engine boats have SAE rotation on both port n stb engines
the port trans is just put into rev to go fwd,but the input into the trans is the same.
Call ZF n Im sure they will help
If u want send me a private message n I can tell u who to talk to
|01-26-2012 02:56 PM|
Back from the dead!
It occurred to me that I never brought this thread full circle. Not that the story is *quite* complete yet, but I can at least bring it current...
We didnt finish the boat in time to get it in the water in 2010. The structural work took longer than expected, as did the final rigging of the engine, running gear, and other misc projects that we tackled "while we were in there".
So the motor sat largely finished until late spring, 2011- it looked like this:
We broke it in properly- used a generous amount of EOS (poured right into the valley), 30w Valvoline VR1, primed the oil pump, used only the outer valve springs, etc. Varied the RPM a little +/- 2500rpm for 25 min, then shut it down and changed the oil.
After reinstalling the valvesprings and rockers, we dropped it in the lake for the first time in 2 years. It ran great! The caveat: after 2 laps around the lake, we found water in the oil. Traced it back to the shiny aluminum exhaust manifolds (which I had bought used on good faith). We stuck the old cast iron manifolds back on, changed the oil several times until it looked clear (we started out with Mobil1 15w50 and ended up with VR1 20w50)... and all seemed well for a few weeks- the stock manifolds seemed to rob 200-300 RPM from the top end, but it otherwise performed great. I took it out to an annual owner's reunion where it came up just short of the "fastest boat" award (58.4 mph). Not bad!
Our glory was short lived, however... in a bonehead move, I overheated the engine after picking up some weeds and hydrolocked it. So I went home with my tail between my legs. Did a little bit of investigating over the next few weeks. Water kept finding its way into the cylinders after sitting for a while. Did a compression check and it came back fine. Pulled the intake, the valley looked clean (no trace of water). We are pretty confident in our diagnosis... the overheat cracked the stock exhaust manifolds. Tore the heads off too, just to be safe- and all looked fine. So we ordered new manifolds and started to reassemble everything... and just as we were about to close it up, I discovered this on cyl #7:
Upon closer inspection, the cam was beat up too. Dammit!
So that put an early end to our summer, major bummer.
So now the question is, what to put back in? Comp is now out of reverse rotation blanks- but we have 2 spares that we ordered 2 years ago. So we could go back with another flat tappet. Or... we're considering going roller. This isnt an inexpensive proposition, but we found someone who has invested in a small run of reverse rotation billet blanks, that can be used with our existing gear/gear timing set. We'd be looking at $750 for the cam, plus $525 for the lifters (the cam builder only uses Morel's "race" version), plus another $200 for new valve springs. So ~$1500 for the upgrade.
Its a big dollar upgrade on a project that is already overbudget by a long shot... but I REALLY dont want to tear this motor out again anytime soon. I suspect I know what the answer will be, but any input or advice would be appreciated!
|03-10-2010 12:18 PM|
No response necessary, I suppose- I confirmed that its a 4-bolt. Still getting my eyes calibrated on the BBC... first time tearing into the bottom end of a motor as well.
Question about valvetrain... Ive read a few threads on here that suggest the stock stamped rockers arent the best to use with aggressive cams. I dont think my XM278H (.555/.565) would be considered all that aggressive compared to some of the builds Ive seen here, but Im not sure exactly what the limitations are of the stock rockers. Should I be ok to run them? Im toying with the idea of upgrading to full rollers (I doubt I would bother at all with roller tips)... probably go with Crane or Scorpion. Anything else I should be aware of before pulling the trigger on a set? I'd be sticking with the stock 1.7 ratio. I figure a new set of taller valve covers will be in order as well.
Thanks in advance!
|03-08-2010 11:04 AM|
Ok, its been a month... quick update here.
I pulled the cam and sent it to Comp. The tech wanted to confirm the exact cam we had before he custom ground a new one. Turns out the blanks lined up perfectly... so the XM278H should be on its way soon. I also convinced him to sell me a RR blank, as there seem to be very few left. Should cover me for any future plans.
While it was there, I had them measure up my stock cam so I could do a delta on the desktop dyno. Looks like the experts here were right- the thing was tiny! .459/.478, 213/216, 112 LSA. Desktop dyno shows 368hp @ 4500 RPM... which would explain why we didnt go faster with a smaller prop (5200 vs. 4900 RPM). If the software is accurate, we'll lose 10-15hp below 3000 RPM (easily offset with the weight loss) and almost 90hp at the peak. The biggest delta will be at high RPM's- we're looking at picking up around 200hp at 5000 RPM's... yikes! It will be VERY interesting to see how the boat performs in a few months! Heres the preview:
We also pulled the pan to check out the bottom end... havent measured the clearances yet, but at a glance, I believe this may be a 4-bolt block. Am I correct?
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