speed for a sportcruiser

[Elim86]

Hey guys, im looking for some ideas on finding a little more speed out of my 1986 20' sportcruiser.It has a 454 with merlin vr heads and merlin intake, holley 850 double pumper, comp cams extreme marine cam, .564 intake and .566 exhaust lift. I cant remember the duration at the moment. The short block is stock marine with zero gap second rings. Pump is berkley JG with an aluminum A impeller. Right now it does 68 on gps @ 5200 and id like to see 72-75 from this if its possible without spending megadollars. Thanks for any help.By the way it also has a Hydraulic place with the so called ride plate and a droop of unknown make.One more fact i forgot is it has factory exhaust logs, I think Hardin exhaust.
[This message has been edited by Elim86 (edited May 16, 2002).]
[This message has been edited by Elim86 (edited May 16, 2002).]

[flat broke]

Well,
The best investment you could probably make is some better flowing exhaust. That way you'll be able to reap the full benefits of any additional changes you make. I would guess that a set of Lightning water jacketed headers would be worth around 200 RPM, which according to the JPC would get you to around 497 HP which in turn should yield 73 mph. Of course to me, a set of lightnings is in the "mega dollar" category at 2k, but you'll be able to use them with whatever you do to the motor.
The other option is to put that BBC on the bottle. That should only cost you about $400 for the Nitrous, plus any other expenditures to bring your fuel and spark systems up to snuff.
Short of that, I guess you could try and score a decent used blower and run a low boost level to pick up some additional HP.
On the Free or close to free tip, perhaps you could adjust your rideplate to give you a slightly looser set and free up a little more hull.
Hope that helps,
Chris www.liquidaddiction.net (http://www.liquidaddiction.net)

[kojac]

Flatbroke is right about the exhaust.
I had a 20ft merlin daycruiser with a stock 454mercruiser jet. It had a stock berkley 12jg pump. Top speed was 52 miles at 4500 rpms. I pulled motor and pumped up the compression to 10-1 and installed a comp cams 292 hydraulic cam, Boat ran 56 miles at 4800rpms. Changed from stock intake and 600 holley - to edlebrock 5.0 intake manifold.The boat increased to 58 mph at 4950rpms. Took off log exhaust manifolds and determined that the outlet squeezed down to 2and1/2" enlarged outlet to 3.1/8 inches. Boat increased to 60 miles at 5100rpms. I felt that the log manifolds were still too restrictive due to there configureation. Installed Edelbrock rpm manifold with a 750 holley double pumper. Boat ran 64 mph at 5250 rpms. Changed exhaust to Bassett over the transom headers 2 1/4" primaries 4"collector 32"long primaries.boat ran 70mph at 5550rpms. Changed cam to cranecam lift .554 intake and exhaust. Duration 254-262 lobe center 110. The boat ran 74mph at 5650rpms The daycruiser was a heavy jet. Pulled motor and exhaust out of daycruiser and installed it in my brothers Light 18ft mantra. and mantra does 89mph in quarter on the decauter radar.
Exhaust should be the first change to allow all other enhancements to work to their max.
kojac....

[Elim86]

Thanks for the thoughts, I was thinking of putting it on the bottle, maybe a 100 horse shot or so. The headers for me are in the mega dollar bracket right now. The ignition is all msd, 6al and distributer, maybe having a bottle baby wont be so bad after all. Thanks again for the idea's.

[apollo74]

Originally posted by Elim86:
Thanks for the thoughts, I was thinking of putting it on the bottle, maybe a 100 horse shot or so. The headers for me are in the mega dollar bracket right now. The ignition is all msd, 6al and distributer, maybe having a bottle baby wont be so bad after all. Thanks again for the idea's.
just curious, what compresion are you running?

[SPECTRABRENT]

Elm86,
If you want to make your cruiser faster and still keep it realiable, go with a larger cubic inch motor 502 or 509. You already have the heads & manifold.
Brent

[flat broke]

Originally posted by SPECTRABRENT:
Elm86,
If you want to make your cruiser faster and still keep it realiable, go with a larger cubic inch motor 502 or 509. You already have the heads & manifold.
Brent
Brent,
Somethin tells me that if Lightnings are big dollar items in this equation, A 509 is going to be asinine. http://free.***boat.net/ubb/smile.gif On a serious note, I should have the 20 fired up tomorrow afternoon, and maybe if I can weasel it, take it out for a shakedown on Sunday. If not, I'll run it on Monday, but I'm definitely itchin at this point.
Elim86,
If you do decide to run the bottle, make sure you do your homework. It would suck to blow your mill and then have to spend a ton of money just to get back to where you are today. Plus think of it this way. From what everyone seems to be saying about the lightnings, running a set might just uncover a similar amount of MPH without the risk.
Good luck,
Chris

[Elim86]

Apollo the compression is 9.1. More cube's or headers are out of the question right now. I allready had the pleasure of passing a decible test, 82db allowed, passed, but the exhaust was so plugged I couldn't break 50 mph. I figure headers would make the thing louder than with the logs.