friends rogers jetboat

« **on:** July 06, 2009, 01:12:56 PM »

A buddy of mine has a rogers jet with a 496bbc 10:1 roller cam and a set of the marine merlin heads. Single 1050 dominator and a berkley with a b cut imp. The boat ran a gps's 79mph at elsinore friday on the way back to the ramp. It pulled 5600 rpm. According to the charts he is not even making 500hp. I just dont buy it. Motor runs perfect, has a nice roller cam. And the jet is new. Are these charts full of shit?

« **Reply #1 on:** July 06, 2009, 01:26:58 PM »

Quote from: trmn8ter on July 06, 2009, 01:12:56 PM

A buddy of mine has a rogers jet with a 496bbc 10:1 roller cam and a set of the marine merlin heads. Single 1050 dominator and a berkley with a b cut imp. The boat ran a gps's 79mph at elsinore friday on the way back to the ramp. It pulled 5600 rpm. According to the charts he is not even making 500hp. I just dont buy it. Motor runs perfect, has a nice roller cam. And the jet is new. Are these charts full of shit?

Is that the Berk chart, or Extended RPM chart?

« **Reply #2 on:** July 06, 2009, 01:31:34 PM »

Also, 5600rpm is respectable with a B impeller. On a hot, humid day.... robs quite a bit of horsepower, and the motor is still making "realistic" numbers, not like the dyno numbers you hear that get tossed around alot with "correction factors". Wait til winter, on a very cool dry morning, at the salton sea, and then see what you get

« **Reply #3 on:** July 06, 2009, 01:44:18 PM »

berkley chart. I am not a chebby guy normally, but I can make 500 hp with a pump gas 347 small block ford with my eyes closed. I just cant get myself to believe a 496 bbc with a descent head only makes 1hp per cubic inch.

« **Reply #4 on:** July 06, 2009, 01:53:54 PM »

Quote from: trmn8ter on July 06, 2009, 01:44:18 PM

berkley chart. I am not a chebby guy normally, but I can make 500 hp with a pump gas 347 small block ford with my eyes closed. I just cant get myself to believe a 496 bbc with a descent head only makes 1hp per cubic inch.

First of all, show me this pump gas 347

Again, you're comparing a corrected dyno number, to a real world, shitty air, test.

« **Reply #5 on:** July 06, 2009, 02:24:05 PM »

I am in Rancho cucamonga, I can show you a 512hp to the rear wheels 347. Its for sale too. I have no dyno numbers on his boat but I drag racfe alot and when I go from here to vegas I only lose about 200 rpm at the most, and thats during the summer. That 200 rpm is about a 10th and a half.

« **Reply #6 on:** July 06, 2009, 02:42:09 PM »

Quote from: trmn8ter on July 06, 2009, 02:24:05 PM

I am in Rancho cucamonga, I can show you a 512hp to the rear wheels 347. Its for sale too. I have no dyno numbers on his boat but I drag racfe alot and when I go from here to vegas I only lose about 200 rpm at the most, and thats during the summer. That 200 rpm is about a 10th and a half.

Don't know what else can be going on, is it running good? And does the 347 have twin turbos to make that much to the wheels, I thought the blocks broke after 450hp

Sounds cool though, you should enter Engine Masters, that would be a first place for sure

« **Reply #7 on:** July 06, 2009, 02:58:43 PM »

no, would not even come close. Motor runs 10:30's here at fontana all motor. Like I said its for sale

Back to the boat, it runs great. Only had a needle and seat problem that was easily fixed. I just thought it would take more than 500hp to run that fast in a jet. But I am just learning about boats.

« **Reply #8 on:** July 06, 2009, 03:09:06 PM »

Quote from: trmn8ter on July 06, 2009, 02:58:43 PM

no, would not even come close. Motor runs 10:30's here at fontana all motor. Like I said its for sale

Back to the boat, it runs great. Only had a needle and seat problem that was easily fixed. I just thought it would take more than 500hp to run that fast in a jet. But I am just learning about boats.

Sure it would, Jon Kasse's motor made 1.2hp per cubic inch, and yours is making 1.65

Back to the boat. There's a TON of factors, and those horsepower charts aren't the Bible of horsepower tellings in a boat. Pump could be overloading, underloading, could have a bat thrust bearing, some parts might not be working in Harmony with each other. The RPM charts are just a estimate guess of what horsepower it could be making.... but if the motor is running good, best bet is just to start playing with set up on the pump and boat to try and fine tune it

« **Reply #9 on:** July 06, 2009, 03:43:52 PM »

There are rules to that competition, there are comp eliminator motors at 360 cid that make over 800.00 all motor. I got monies to back it up if there are any takers. 500hp 347cid is no big deal with the cylinder heads available today. my superstock 302 motor makes 440 to the crank. 8.8 to 1 compression stock block crank and rods. Stock heads with no porting, victor jr intake , stock carb from the factory (86 mustang in this case) roller cam. Ran it for 2 years and Im no genius. I just dont buy the acuracy of the charts is all. Are there any jet dynos out there? That would be cool. Im pretty sure 500 hp wont go 79mph in a jetboat with 2 big guys and 1 girl in it. Maybee it will I dont know.

« **Reply #10 on:** July 06, 2009, 03:45:52 PM »

whats the deal with this overloading and underloading of the pump. Jim Guthrie did the pump in both our boats and they seem good. His does not have a inducer and mine does. Thats is the only difference there.

« **Reply #11 on:** July 06, 2009, 04:06:24 PM »

im running a 4.3 liter v6 in my boat 250 hp and getting 52 mph gps out of it so i think that it would be able to do that,but im no genius this is my first jet

« **Reply #12 on:** July 06, 2009, 04:08:19 PM »

Quote from: trmn8ter on July 06, 2009, 03:43:52 PM

There are rules to that competition, there are comp eliminator motors at 360 cid that make over 800.00 all motor. I got monies to back it up if there are any takers. 500hp 347cid is no big deal with the cylinder heads available today. my superstock 302 motor makes 440 to the crank. 8.8 to 1 compression stock block crank and rods. Stock heads with no porting, victor jr intake , stock carb from the factory (86 mustang in this case) roller cam. Ran it for 2 years and Im no genius. I just dont buy the acuracy of the charts is all. Are there any jet dynos out there? That would be cool. Im pretty sure 500 hp wont go 79mph in a jetboat with 2 big guys and 1 girl in it. Maybee it will I dont know.

If you try to make automotive practices work in a boat, you will not be successful, period end of story. you say 800 hp this and that, but at what rpm? If you make 800 HP at close to 7000 rpm, that would have to be one badass billet built pump to be able to put up with the abuse...

Don't get me wrong, but 500 HP on a BBC is pretty respectable given the same engine from the factory version of the same motor barely broke 300 HP. You cannot compare an automotive engine to a Jet boat engine, the load simply never lessons like in a car, the load increases until accelleration stops, that's it, no compromises.

For an engine to make a good jetboat motor, peak torque should be at a higher RPM than on a car, since torque is a major mathimatical component of HP, the WOT RPM will be lower to get them close (425ft/lb at 425 HP is the middle of the road).

There is no way a good running automotive type build will run well in a jet (build meaning cam, lifters, rockers, carburetion, ignition, compression yada yada...)

Also,just because a BBC has a roller cam don't make it a good motor, could very well be the wrong cam or even timed wrong or the tune up could be missing by a mile.....

There are some good threads here and the search feature works well, check out some of the threads on pump loaders and other setups, I think you will be suprised how complex it can be...not as cut and dried as you may think it is....

Welcome to our nasty habit

GT

« **Reply #13 on:** July 06, 2009, 04:24:27 PM »

Wow, I did not know marine stuff was so different from auto. I mean yah the camshafts but lifters and cars too? Im gunnu get a outboard f it. My southwind runs good enough for me, My buddy thought his would run better than it did is all, and when I saw the chart from berkly I was surprised at the numbers is all. I mean can a jetboat making 500 crankshaft hp run in the 80's in a older hull? I know you probably could in a race hull like a cp or something.

« **Reply #14 on:** July 06, 2009, 04:27:24 PM »

Quote from: trmn8ter on July 06, 2009, 04:24:27 PM

Wow, I did not know marine stuff was so different from auto. I mean yah the camshafts but lifters and cars too? Im gunnu get a outboard f it. My southwind runs good enough for me, My buddy thought his would run better than it did is all, and when I saw the chart from berkly I was surprised at the numbers is all. I mean can a jetboat making 500 crankshaft hp run in the 80's in a older hull? I know you probably could in a race hull like a cp or something.

The question is, is that 500 corrected horsepower or uncorrected

And yes they can, just takes trial and error. An honest 80mph river boat will beat 90% of boats on a weekend... just stay away from the races lol

« **Reply #15 on:** July 06, 2009, 04:43:13 PM »

Quote from: shallow running on July 06, 2009, 04:06:24 PM

im running a 4.3 liter v6 in my boat 250 hp and getting 52 mph gps out of it so i think that it would be able to do that,but im no genius this is my first jet

250 HP out of a 4.3? they came from the factory with only 205 HP. What's been done to it? I have a Kodiak Marine 4.3 Vortec I would love to build up.

GT

« **Reply #16 on:** July 07, 2009, 11:48:21 AM »

Quote from: GT Jets on July 06, 2009, 04:43:13 PM

250 HP out of a 4.3? they came from the factory with only 205 HP. What's been done to it? I have a Kodiak Marine 4.3 Vortec I would love to build up.

GT

it is a 4.3 mpi running corsa performance thru hull rated at 225 hp on a volvo prop drive so im just guessamating but gaining the 10% loss going thru the gears that would add 22.5 hp at the crank making it 247.5 hp i rounded it off to 250 hp

« **Reply #17 on:** July 07, 2009, 12:05:10 PM »

I read somewheres that a jet pump sucks up somewhere around 30% of crank horsepower. Example - 100hp=70hp. Maybe that could be an answer as to why a well built engine isnt quite what everyone expected.

« **Reply #18 on:** July 07, 2009, 02:39:06 PM »

Quote from: trmn8ter on July 06, 2009, 01:12:56 PM

A buddy of mine has a rogers jet with a 496bbc 10:1 roller cam and a set of the marine merlin heads. Single 1050 dominator and a berkley with a b cut imp. The boat ran a gps's 79mph at elsinore friday on the way back to the ramp. It pulled 5600 rpm. According to the charts he is not even making 500hp. I just dont buy it. Motor runs perfect, has a nice roller cam. And the jet is new. Are these charts full of shit?

I don't know much about this stuff, but here's what i'm running.
19' Rogers with a 427bbc, 30 over, 12:1, solid lifter cam(actual total lift 600), old closed chambered heads, Holley marine 850 carb, and a fresh c-cut ss impeller with an inducer. Best its done is 80.6 at Parker running 5800 - 5900 rpm's

« **Reply #19 on:** July 07, 2009, 02:55:09 PM »

They Probably run very simular, except the cid difference and you have more compression. The cid probably explains the rpm difference.

« **Reply #20 on:** July 07, 2009, 03:43:50 PM »

Quote from: trmn8ter on July 07, 2009, 02:55:09 PM

They Probably run very simular, except the cid difference and you have more compression. The cid probably explains the rpm difference.

I figured I would post up my specs to show that your friends boat sounds about right.

« **Reply #21 on:** July 07, 2009, 04:15:40 PM »

My Southwind runs a little better, only diff is I have a inducer and a tunnel ram. Same cylinder heads compression almost the same I have 10:2 Mine turns 5700. I am going to change the cam but I decided to wait till the off season. Im having to much fun with it the way it is...

« **Reply #22 on:** July 07, 2009, 07:45:07 PM »

MY-my what an intersting thread... Motors alone don't make speed in jets. Of coure it's important but not the end all. Bottoms, pump hardware, elbo grease, trial and error, accurate equipment. 1978 my Eliminator Daytona ski-jet II(+.030 454. 750 holly, drake log exhaust, AFR Heads, Roller cam, etc.) with Berkley not to far from stock, ride plate, taper shoe and loader took a timing slip at the APBA Kilo's of 93 MPH missed the record, went to a Rodgers. What ever "Chart" you have ignore it. Have fun and keep up reading the forum.

« **Reply #23 on:** July 07, 2009, 08:17:52 PM »

Quote

If you try to make automotive practices work in a boat, you will not be successful, period end of story.

Quote

MY-my what an intersting thread... Motors alone don't make speed in jets.

Very good info, Just in those quotes! I'm from a hot rodding background on this too and really just getting a grip on all this. Those 'charts" you refer too are really just guidelines based on generalities. I think the idea is to aim the peak HP rating and RPM it hits that number at the chart and select your impeller from there. I think this is a bad practice, myself. While maybe a good STARTING point, you'll still have to experiment going up and down impellers to best match your engine/pump combination IMHO. (The Moo I got pretty lucky, but still plan to test a B AND an AA over the winter in her).

And They're right, much more to it than just the engine/impeller. Cav plates, loaders, how tight or fresh the pump is, how it's mounted, even down to what paint is on the bottom of the hull and how it is applied and it's texture.

76MPH is easy for me to beleive as the Moo can do that at will. Blind squirrels find acorns once in a while! Just don't bank on the charts saying this isn't possible. The end goal is total efficency of the entire system, and in a Jet Boat, not an easy thing to tweak sometimes. (Ask Jeff, he has his hands full tweaking his former drag boat).

HP ratings and what we get from a dyno to real world applications is a different matter. And to my opinion, it doesn't really matter, as long as the engine is solid and can reliably drive the intended drivetrain and connected vehicle to the desired results consistently and not break, I'm down with it!

Just my .02

Ray

I say this as I'm building something totally INSANE that was supposed to be a cruiser, lol.

« **Reply #24 on:** July 08, 2009, 09:26:35 AM »

I buy it. Max MPH and max RPM are a reflection of hull weight and how it's riding, hardware setup, hydrodynamic design of the hull, pump efficiency, etc etc. My 18' Marlin with an AB impeller GPSed 79 @ 5400RPM last season and is now at 77 with an A impeller turning 5200-5300 RPM. That's with no shoe or rideplate.

Also from what I've read, Rogers boats have very good bottom designs so it's totally doable.

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