Learning Experience

[PaulO]

For all of you who are looking to improve the top speed performance of your 18 classics, here is what I have done and the results (all with GPS):

1973 18 2+3, bone stock 350 chevy, Volvo 280 drive, Ultra prop 22 pitch, 1.63:1 ratio. Top speed 58-59 at 5000RPM during ideal conditions (no gas, good chop, no breakfast, tailwind, etc.) Lousy steering, no power trim. A handful at speed. Replacing steering cable and outdrive bushings improved steering immensely but did nothing for torque steer.

Upgraded to Merc 260 w/Alpha drive for speed and power trim/steering, 21P mirage plus. 260 not exactly "fresh". Relocated steering to starboard. Huge handling improvements. Very safe feel. Power steering a pleasure, no torque steer. Top speed 61-62 at 4700 RPMs more consistently. Cost approx. $2200
including donor boat $1600, prop, and misc parts.

Upgraded to 383 stroker motor. All the goodies including rods, heads, intake, roller cam, etc. 415 HP at 5200 RPM 430 Ft.Lbs of torque. Top Speed 65-66 at 5000RPM with 23P vengeance prop. Great cruise speed. Can run 50-55 all day in the 3800-4000 RPM range.
Cost- $3600, $3400 for engine + misc.

Upgraded from Q-jet carb to Prepped Holley 750. No speed increase. Runs better at part throttle. Needed to change manifold to accept spread bore. Cost- $600.00

Interesting observations:

Tried 21P cleaver prop. Gained 300 Rpms and lost 1 1/2 - 2 MPH.

Same results with 21P Mirage.

Thought that maybe 750 Cfms with mechanical secondaries would be too much carb- nope takes it all without any hesitation.

Net result:
Too much money and not enough speed increase. 65 feels very fast. I pass all sorts of boats that claim to be faster.

Lesson: It takes all sorts of power to produce incremental speed gains.

I am not unhappy but, really thought 70 was obtainable. Maybe a stern jack or SS drive next year. Maybe a faster hull.

PaulO

[CDMA]

PaulO,

Interesting experiences. For those who do not know I have the complete Chevy Volvo set up out of Paul O's boat before he switched to Mercruiser. I have gone the exact opposite route with left hand steering and the old tech drive. Over this winter I am switching to Hydralic steering and a new 355 with abot 330-350 hp. I am really suprised to hear that 65 was all you could get. I am running a solid 57 and 65 is what I figured was possible with a nice 350 and the Volvo but maybe I am wrong. Sounds to me like you are going to wind up with a faster boat.

Chris

[BERTRAM BOY]

Hey Guys,
I had my boat out on Saturday, and did a few "top speed" runs. With me, and a 150 lbs. passenger(I needed someone to hold the gps) and full fuel we just barely hit 62(62.1). I'm wondering what the effects of a nose cone might be. I know that Volvo speedmasters are difficult to find, and impossible to find parts for, but 8 mph!!! that's a lot of free speed!!!! Does anyone know who make a nosecone kits for Volvo's?
Geoo, you used to have one didn't you?
BERTRAM BOY

[PaulO]

I still have some more tweaking to do but, judging by past experience, I will be lucky to wring another 2 MPH out of this setup. Some more jetting and prop swaps maybe. I think that in order of likelyhood I may do the following in the future:

CD ignition
Stern Jack
Alpha SS
Aftermarket Exhaust
Just try to enjoy it

PaulO

[CDMA]

Cliff,

I have what used to be Geoo's nose cone. I do not know what brand it was but there is no measurable difference in speed at all. Does look cool though.

Chris

[GEOO]

BB,
I tried a Hydromotive nosecone on my Volvo 290. The steering felt better I lost 1 mph top speed.
When I had a Volvo 290 with trim and a Ultra 26" cupped. I ran a 383ci with Sportman II heads unported, my mechanic built two engines the same, the other engine dyno'd at 360hp with CMI exhaust. My boat ran 62-64gps mph approx 350-360hp (Stainless Marine Exhaust). The next year I installed AFR Alum. ported heads. approx. 380-400hp. The boat ran 64-68gps,radar.
An Alpha drive should go faster then a Volvo 270-290. Our boat's need about 10 to 12 hp to go 1 mph faster. GEOO

[BERTRAM BOY]

Alright,
So now I'm really puzzled!!! Does that mean that all those legendary claims for the Speedmaster are "exagerrated" or is there something else about the Speedmaster that's different than just a nosecone? Yeah, I know that an Alpha would probably be faster, but I just don't whan to give up the the strength of the Volvo. I plan on repowering in a couple of seasons.
I feel really lucky to be running as fast as I am with about 100 hp less than you had George. I didn't realize how much gain I get with drive raised up. Although I am overreving I bit. I'm running about 5300rpm
George, How much gain did you see with your Speedmaster over the stock drive?
BERTRAM BOY

[GEOO]

BB, A speedmaster, "E-Drive" is a complete lower unit that bolts on. The drives bullet is only about 4" dia. compared to 5 1/2 or 6". Check out the photo of the drive on the ground. http://www.donzi.net/tech/DonziArneson.htm
When I bought the drive the boat went 68 on Monday and 77 on Tuesday!! 8 to 10mph!!!
A nose cone only added more drag when I trimmed the drive up. GEOO

[BigGrizzly]

I have a Corsican 18 with a 351 Ford Clevland. when i got the boat it had a loose steering Volvo 270 and a H&M motor. This would pull 56mph. My present set up will go 64.7 on GPS with full fuel and a Gps holder(two legged kind),and no beer or ice. this engine is 0.030 over stock bore Babe Erson cam, Weiland intake, Volvo 290 drive(took gears out of the 270 I only change one thing at a time) a Ron Hill 15x23 Thrasher prop a Hydromotive nose cone, and a 750 Holley 4010 carb and CMI exhaust. This unit will turn 5600 if I let it. The nose cone did nothing for the speed. they will tell you it doesn't help under 75 or 80, they told me that. It did stablize the boat. Speed came from cams and exhaust system. Head work only matching ports and I did a 3 angle valve job stainless steel valves. The crank is even stock. I too beat many "72" mph boats. Joke around this lake is someone has a box of these speedos.
CDMA, I do beleive you can do 65mph with that motor. Rember what I have told you about the complete setup, cams and such? There is a trade off, you can't have it all. I have the ability to do 70 but the tradoff is too great for me. The cam is the heart of the power. I don't care what heads what carb what compression, or what ignition you have, (short of a blower) the gains will be small if the cam isn't changed. Have you heard this one before,"I just spent all winter hopping up my motor and it pulls less rpms".

[This message has been edited by BigGrizzly (edited 09-11-2000).]

[Ralph Savarese]

I had a nose cone on my volvo drive it was called a springfield bullet i guess it is what they used on outboards.
i had it bonded with marine tex to my outdrive and flared it in nicely.
Well when i happen to drop the the bottom of the drive on the cone this year it cracked off there is obvious difference!

[RichF]

Originally posted by PaulO:
I still have some more tweaking to do but, judging by past experience, I will be lucky to wring another 2 MPH out of this setup. Some more jetting and prop swaps maybe. I think that in order of likelyhood I may do the following in the future:

CD ignition
Stern Jack
Alpha SS
Aftermarket Exhaust
Just try to enjoy it

PaulO

Hi Paul:

The need for speed.....where does it stop? http://www.donzi.net/ubb/biggrin.gif.. maybe you should go with option 5Just try to enjoy it, or else you may be at option 6... Get thrown out of house by wife for ongoing boat upgrades! (just kidding)



[This message has been edited by RichF (edited 09-12-2000).]

[seano]

Guys,

I'm told that nosecones are only effective if you are already achieving speeds greater than 80 mph. Now, that's what I've been told for the Bravos....has anyone heard the same for Alphas, Volvos or the various outboards?

[GeneD]

PaulO,
I feel terrible that the 750 didn't do anything.
Kinda weird!?!?
But the speeds you are doing are pretty damn respectable. I think you are right though, an SS or X dimension change would really do it.
Who was the guy that changed his X dimension and was getting great results? I think this is the final key needed to open the door for speed.

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GeneD
007
Melbourne, Florida

[PaulO]

Gene,
I was surprised as well. I am fattening up the jetting on the carb this weekend at the suggestion of the carb builder. Anyway, the boat runs better at mid-range and idle than it did with the Q-Jet. I changed carbs also because I think that my Q-Jet was in need of some work. If I can get the right conditions, I will attempt to dial-in the ignition advance also. I After rebuilding that transom, I will not be changing the X-dimension. There is not enough hatch clearance anyway to raise the motor/drive up. I will keep my eyes open for an SS.
PaulO

[RickSE]

PaulO,
Running richer jets will probably cause you to loose power, lean mixtures generally make more power. I've leaned out the 650 Holley on my motor as much as I can and it really runs great now. It's a totally different application but I run 67 jets in front and 70's in back, on my 350 @ 3700 ft elevation, 4150 650 CFM. It runs awesome now and I've almost totally eliminated the black soot on the back of the boat. If you have room you may want to try a 1" phenolic spacer under the carb, this will lenghten the runners and insulate the carb. Your probably right in that ignition timing is your next step.

[GeneD]

There was a guy a while back that told me he knew the location of 2 Alpha SS's. He never got back to me!
I'm gonna try and get a hold of him.
BTW, doing final assy on my 1995 5.7 Factory Roller Cam Mercruiser.
Check it out!
I love that PhotoPoint page, don't you all?

http://albums.photopoint.com/j/View?u=1173240&a=8637561&p=28469570&Sequence=0&res=high


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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 09-15-2000).]

[Jamesbon]

GeneD,
You really running a dual quad intake? SAWEET!!

Nate
Left Coast Boater

[GeneD]

Nawwww!
Just teasing.
That is my new roller cam 5.7 though underneath.
Beware all you SB people, I'll be tearing up the river in a week or so!
Make sure you get high octane 'fore you see me!

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GeneD
007
Melbourne, Florida