Rpm and Horsepower limits TRS?velvet Dr.
04-22-2003, 05:53 PM
#1
Guest
Posts: n/a
Rpm and Horsepower limits TRS?velvet Dr.
Hail fellow speed freaks!
I own a 30' Stuphen Oceanpacer and its getting the TOTAL package re-do. The Motors are new 468 4bolt, polished crank, rods, 575hp natural Merc spec cams, Merlin Grumpy Jenkins 310cc
square ports, Speed Pro 10:00-1 coated pistons, Crane Gold roll.ro., Chevy Marine High rise manifolds, 780 Holleys(worked...possibly 1100 dominators) complete MSD ign. Gill off-shore set-ups. All balanced and printed and built by Camco Racing Engines in Weymouth MA. Hp #s are 510-525hp with the Holleys and 525-550 with the Dominators...both at 5000-5200rpm.
My problem is this: the builder says these motors would make close to 600hp at 6500-7000 and will spin up there just fine for short stretches...the 5200rpm limit we gave ourselves is the agreed limit to the drives and trans. Is this right? If it is, thats fine, but if I can go to 6500 land, I'm buyin. Is there anything besides building the trans up that I can do to keep from going terminal? I'm a working slob so I REALLY can't afford to spin drive gears or trans housing pieces through the engine hatch.
I own a 30' Stuphen Oceanpacer and its getting the TOTAL package re-do. The Motors are new 468 4bolt, polished crank, rods, 575hp natural Merc spec cams, Merlin Grumpy Jenkins 310cc
square ports, Speed Pro 10:00-1 coated pistons, Crane Gold roll.ro., Chevy Marine High rise manifolds, 780 Holleys(worked...possibly 1100 dominators) complete MSD ign. Gill off-shore set-ups. All balanced and printed and built by Camco Racing Engines in Weymouth MA. Hp #s are 510-525hp with the Holleys and 525-550 with the Dominators...both at 5000-5200rpm.
My problem is this: the builder says these motors would make close to 600hp at 6500-7000 and will spin up there just fine for short stretches...the 5200rpm limit we gave ourselves is the agreed limit to the drives and trans. Is this right? If it is, thats fine, but if I can go to 6500 land, I'm buyin. Is there anything besides building the trans up that I can do to keep from going terminal? I'm a working slob so I REALLY can't afford to spin drive gears or trans housing pieces through the engine hatch.
04-22-2003, 06:01 PM
#2
Geronimo36
Gold Member
I know of a lot of guys who would run 6500 rpm limits on small blocks with your setup on a 30 ft Sutphen. It was the old Great Adventure boat. They had no real problems with the drives or trans from what I was told.
But from a longevity standpoint, I wouldn't run that high. When those springs get a little older you run a higher risk of valve float, also things get hairy turning that hight. I hope everything is balanced?
You may also loose a lot of cruise speed running that high RPM because you will be turning smaller wheels to achieve max hp. You may only cruise at 45 mph at 3500 rpms with that setup. Running 5200 rpms max with larger wheels may net you a 55 mph cruise. One question though? Why is your mechanic putting in a Cam that makes a lot of power in that RPM band? You may want to run a different cam if you plan on turning 5200 rpm?
Just my opinion
Panther
Good luck with the boat!
Panther
But from a longevity standpoint, I wouldn't run that high. When those springs get a little older you run a higher risk of valve float, also things get hairy turning that hight. I hope everything is balanced?
You may also loose a lot of cruise speed running that high RPM because you will be turning smaller wheels to achieve max hp. You may only cruise at 45 mph at 3500 rpms with that setup. Running 5200 rpms max with larger wheels may net you a 55 mph cruise. One question though? Why is your mechanic putting in a Cam that makes a lot of power in that RPM band? You may want to run a different cam if you plan on turning 5200 rpm?
Just my opinion
Panther
Good luck with the boat!
Panther
04-22-2003, 10:40 PM
#3
Guest
Posts: n/a
Panther
Thanx for your information...it will be very herlpful. The cam chosen was one of three that World products recommended to run with my displacement and cylinder head choices...the band was the most usuable with this grind, 2500rpm to 7000 with 1.7ratio rockers. The others piddled out at 4800 and the other end of the spectrum, 8000 rpm. He wanted the meat of the power to start in at about 3500 and still be strong at 5000-5200. This cam seemed by far the best compromise...barring my undisciplined throttle hand and OBSESSION with revs and power, it would function well with the right wheels.(My first REAl car had a 388sb chevy that routinely hit 9000 first to second and second to third...for two years.)Any how using sound advice from others as well as yourself, I'm going to prop for 5200-5500 with rev limiters at 5500(the wonders of technology!). That also decides my carb choice as the 780 Holley will be perfect for that range...not to mention fuel bill. Thanks again for the luck too. It seems like alot of people really think highly of these boats...makes me feel better.
Thanx for your information...it will be very herlpful. The cam chosen was one of three that World products recommended to run with my displacement and cylinder head choices...the band was the most usuable with this grind, 2500rpm to 7000 with 1.7ratio rockers. The others piddled out at 4800 and the other end of the spectrum, 8000 rpm. He wanted the meat of the power to start in at about 3500 and still be strong at 5000-5200. This cam seemed by far the best compromise...barring my undisciplined throttle hand and OBSESSION with revs and power, it would function well with the right wheels.(My first REAl car had a 388sb chevy that routinely hit 9000 first to second and second to third...for two years.)Any how using sound advice from others as well as yourself, I'm going to prop for 5200-5500 with rev limiters at 5500(the wonders of technology!). That also decides my carb choice as the 780 Holley will be perfect for that range...not to mention fuel bill. Thanks again for the luck too. It seems like alot of people really think highly of these boats...makes me feel better.
04-24-2003, 05:33 PM
#4
Geronimo36
Gold Member
Just remember one thing. The torque numbers are what you should really be concerned with. You may make 600 hp at 7000 rpms, but the torque drops off at 4800 rpms.
I would run your motors within the torque band of the cam. That has been my best success for overall performance. I have seen a lot of guys set up motors like they were running the drag strip, and set up for high rpm's. They always had to turn high rpms to make power, but the setup in a boat needs to push a lot more weigh, and torque is usually the best number to go by from my experience.
Let us know how you make out
I would run your motors within the torque band of the cam. That has been my best success for overall performance. I have seen a lot of guys set up motors like they were running the drag strip, and set up for high rpm's. They always had to turn high rpms to make power, but the setup in a boat needs to push a lot more weigh, and torque is usually the best number to go by from my experience.
Let us know how you make out
