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Carp,
I agree with Jim, you could get the boat to run 90-100+ MPH but today most of your set-up is not for top speed. To get significantly more speed, it will take major changes that are not in the engine compartment. My 1987 Scarab will run over 100 MPH but I could buy a new 39' Outerlimits with twin 1075's for less than I have spend over the last 20 years clawing up the wall. Ben |
Originally Posted by bcarpman
(Post 2633539)
Just thought I'd post some details on just how bad my hull must be (I say "must be" because we can't think of anything else that could be at fault).
The boat came with a stock 330hp 454. I would run 53gps on a good day with a light load. If you put 5400 lbs, 300pshp into: http://www.go-fast.com/boat_speed_predictions.htm and you get a hull constant of 223 which would seem about right for a conventional V of this vintage. So then I drop a "330 on Roids" in that dynoed at 460hp and the boat barely hits 59or60 gps (Speed calculator says it should hit 63). Oil pump goes south on that engine after about 20 hours with the predicted consequenses. (still no idea what happened) Drop a Tyler Crocket built 502 with 540hp and the boat still feels like it's bouncing off a wall at 60mph (speed calc says it should hit 69mph). The last 30% of throttle yields no speed increase. No amount of drive trim will loosen up the bow. Stock boat used a 21p 3 blade. Newest motor can't even turn a 24p 4 blade despite an extra 210hp. If I run a 25p 3 blade, it blows out before WOT. I really do love this boat for everything other than top speed (It's a really spacious boat for it's size), and everyone commments on how nice it is both outside and in. So I'm not sure what I'd buy that would be as nice. Can't stand the baja's and you have to step up to a 30plus fountain/formula with twins to get a cabin/cockpit that's as roomy and as of now I can't afford that (business has been slow this year). Compromises! Oh well, just rambling now. I bet my hull is similar to yours i seem to have a 60 mph wall 23 ft rinker 3900lbs , 502 carb. best gps 59.x with a couple people in the boat. I went out and looked at the "pad on my boat it is about 2 inches wide only. |
Originally Posted by bcarpman
(Post 2631561)
Anyone know of a Velocity that is sitting out of the water anywhere around me? I'm not looking to buy anything right now, just more looking to learn. The engineer in me is never going to just "use" the boat to go boating. That much I know of myself.
He's got a 30 sitting inside that he used to race, he can give you all the info you want and then some on Velocity. Google the number as I don't have it handy. My 280 Velocity was a fantastic boat, you need to get back on the throttles right before you land to soften the landings, once you learn to throttle it right you're gonig to love it. The 280's corner like a go-kart, non-stepped hull. |
Originally Posted by cass236
(Post 2634098)
I bet my hull is similar to yours i seem to have a 60 mph wall 23 ft rinker 3900lbs , 502 carb. best gps 59.x with a couple people in the boat. I went out and looked at the "pad on my boat it is about 2 inches wide only.
60MPH GPS You should be going faster. My boat used to porpoise a lot. If I still had it I would go to 4-5 blade prop with more cupping to control the nose and get the weight from the motor up. That boat is very transom heavy from the motor and a heavy built transom. If you can get the back up you will pick up speed. A very heavy (in comparison) Wellcraft Nova 23' with a 454 used to go 60 with a 24* deadrise and no pad. I think that boat is better off with a lighter 350 CI Engine Whippled. My .02 |
Originally Posted by Hydrocruiser
(Post 2634180)
I had the same boat with a (330 HP) 454 Mag...21P Merc Mirage prop.
60MPH GPS You should be going faster. My boat used to porpoise a lot. If I still had it I would go to 4-5 blade prop with more cupping to control the nose and get the weight from the motor up. That boat is very transom heavy from the motor and a heavy built transom. If you can get the back up you will pick up speed. A very heavy (in comparison) Wellcraft Nova 23' with a 454 used to go 60 with a 24* deadrise and no pad. I think that boat is better off with a lighter 350 CI Engine Whippled. My .02 Yeah it seems to need a lot of trim. Do trim tabs help? |
Originally Posted by bcarpman
(Post 2633539)
Just thought I'd post some details on just how bad my hull must be (I say "must be" because we can't think of anything else that could be at fault).
The boat came with a stock 330hp 454. I would run 53gps on a good day with a light load. If you put 5400 lbs, 300pshp into: http://www.go-fast.com/boat_speed_predictions.htm and you get a hull constant of 223 which would seem about right for a conventional V of this vintage. So then I drop a "330 on Roids" in that dynoed at 460hp and the boat barely hits 59or60 gps (Speed calculator says it should hit 63). Oil pump goes south on that engine after about 20 hours with the predicted consequenses. (still no idea what happened) Drop a Tyler Crocket built 502 with 540hp and the boat still feels like it's bouncing off a wall at 60mph (speed calc says it should hit 69mph). The last 30% of throttle yields no speed increase. No amount of drive trim will loosen up the bow. Stock boat used a 21p 3 blade. Newest motor can't even turn a 24p 4 blade despite an extra 210hp. If I run a 25p 3 blade, it blows out before WOT. I really do love this boat for everything other than top speed (It's a really spacious boat for it's size), and everyone commments on how nice it is both outside and in. So I'm not sure what I'd buy that would be as nice. Can't stand the baja's and you have to step up to a 30plus fountain/formula with twins to get a cabin/cockpit that's as roomy and as of now I can't afford that (business has been slow this year). Compromises! Oh well, just rambling now. Something doesn't add up. You should definitely be running faster than that. |
Originally Posted by cass236
(Post 2634217)
Yeah it seems to need a lot of trim. Do trim tabs help?
I always ran with my tabs all the way extended downward (when in chop) to keep the nose from bouncing up and down. I gave up and sold it. However, in calm waters I used to have a blast doing donuts around a 4-5 mile imaginary circle course. If I still had it I would most likely contact a custom prop shop and explain the problem(s) and see what they could do. I think the prop needs a lot of blade surface to get the back end up and out and to keep it level. It felt like a 4,000 pound boat with 3,000 lbs in the mid to back section. A balance act is required to get it running right. Work on getting the right custom prop. |
Originally Posted by BenPerfected
(Post 2634040)
Carp,
I agree with Jim, you could get the boat to run 90-100+ MPH but today most of your set-up is not for top speed. To get significantly more speed, it will take major changes that are not in the engine compartment. My 1987 Scarab will run over 100 MPH but I could buy a new 39' Outerlimits with twin 1075's for less than I have spend over the last 20 years clawing up the wall. Ben |
Carp,
If you want some good advice and honest perspective, there is a guy close to you in MI that can help you. Dave Goodman, Tiger Fiberglass, Maryville, MI (810 364 8875). Dave has the experience and can do all the necessary F/G work. He can help you with the necessary X-dimension changes, rigging, bottom work, strake lengthening, etc. Dave is an ex-racer and and is very experienced in set up. He has helped numerous race teams improve their programs. He can also participate in the actually testing and dial-in until it is right. |
This thread has been a lot of help. Thanks to everyone who chimed in.
Two questions I still haven't got answered: 1. Will raising the prop increase bow lift or decrease it? 2. What do the strakes do? they increase surface area which is bad for speed, right? but they provide lift which can be good? Do they provide any stability or resistance to chine walk? Would flattening then out at the stern help with my lack of bow lift? |
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