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chappy
08-30-2002, 08:24 PM
HELLO ALL,
FIRST TIME DONZI OWNER HERE. I JUST BOUGHT AN 87 CLASSIC 18 WITH STOCK 350 MERC MAGNUM. RUNNING A 23 PITCH STAINLESS CLEVER. TOP SPEED I'M GETTING AT 4400 RPM IS 60 MPH. MOTOR HAS 170 HOURS. IS THIS THE MOST I CAN GET OUT OF THIS SET UP, OR CAN I GET MORE WITH A RE-BUILT OUTDRIVE WITH THE RATIO CHANGED? I THOUGHT I SHOULD BE PUSHING 65 MPH. I DON'T HAVE ACCESS TO A GPS, MAYBE MY SPEEDO IS OFF. ANY HELP WOULD BE APPRECIATED, I'M VERY NEW TO THESE SPEEDS. THANKS FOR ANY HELP!

Stix Magill
08-30-2002, 08:42 PM
Welcome to the Donzi.net boards. I have a 1987 Minx 20 and it has a fresh 350 Mag. I have only recently purchased a GPS, but on the first trial I saw 59.5 mph with a full tank and 2 passengers. My speedo was reading much less. Do you have power trim? I think you are going to have 63 to 65 on GPS, if you are trimmed properly. You can get much higher speeds if you spend big bucks. You should have higher RPMS and should consider trying a 21 non-clever if you haven't already. I have read that the clever is best for situations where the hull is out of the water and only the foot is in. You are not running that much power. Just my regurgitation.... the other guys know more and will hopefully add to this.

Let us know what happens!!
Stix

harbormaster
08-30-2002, 08:46 PM
wHAT IS THE RATIO?

Bug
08-30-2002, 09:05 PM
Welcome aboard!! I have a '84 18' 2+3 with a
260 Mercruiser set up which is a 350 chevy 260 hp
I beleive your 350 magnum produces about 280 hp.
On a good day I've had it pushing between
4400-4600 RPMs top speed at 62 MPH, spinning my
Clever 23 pitch.
If it works don't fix it (just my opinion)
Enjoy the ride.

MOP
08-30-2002, 09:37 PM
Hi and welcome to the site glad to have you aboard. I think from what I have been picking up here the 18's need a little bow lift. The cleaver picks up the stern. I think you will do a bit better with a decent regular stlye cupped wheel. I would love to try a cleaver to flatten out my 16.

chappy
08-31-2002, 06:25 PM
THANKS FOR THE REPLIES. I DON'T KNOW WHAT THE RATIO IS, AND I'M LEANING TOWARD NOT CHANGING IT, BECAUSE I'M TAKING THE ADVICE OF ONE OF THE REPLIES, AND NOT GOING TO FIX IT IF IT ISN'T BROKEN. I HAVE A 21 PITCH CUPPED STAINLESS PROP THAT I WILL TRY FROM AN OLD 150 HP MERC OUTBOARD I USED TO RUN TO SEE WHAT IT'S LIKE. BY THE WAY, HOW MUCH FOR A GPS IF I WANTED TO BUY ONE? THANKS AGAIN FOR THE INPUT.

Moody Blu'
08-31-2002, 07:31 PM
hi welcome to the board!

form what I have heard and seen, the cleaver works pretty well with the classic, I know a guy that use to have a 18 with a 23p cleaver andhis boat was hitting 74mph(he had mods)

I am going to try a 25p cleaver next weekend, but next season im going to have a 420w stroker motor so ill need a 30+ pitch prop for it.

theres no harm in trying another prop...
I say try the prop form the outboard.(if it fits)

youll prolly be better off with the 23p though.

also, if you want mor epower I would say to think about getting a set of headers, like gil or cmi...(be glad you have a chevy because its impossible to get a set of marine headers for my ford) :o

but the headers will be a winter project for me..

Rootsy
08-31-2002, 08:09 PM
the 350 mag came with a 1.5 ratio drive as standard. The 23 pitch cleaver and corresponding rpm seem correct for this ratio. Your motor is rated for a bit higher rpm than what you are currently spinning and if you drop to a 21 cleaver you'll be in the 4800 rpm range or a bit more if the motor is strong. In the late 80's i believe the 350 mag was rated @ 270 pshp. If you want a bit more grip and considerably more bow lift you can try a mirage+ or a turbo, likely a 21 pitch since they grab the water a bit better than the cleaver. The turbo tends to be a lot more steady and possibly a bit faster than the mirage+...

Gritz
08-31-2002, 10:31 PM
Late 80'S 350 MAG = 300 HP/

harbormaster
09-01-2002, 07:40 AM
Jamie,
Some 350 mag setups came with 1.62 gearing.

Chappy, Is your magnum carb or fuel injected?

I am assuming you have an alpha.

Rootsy
09-01-2002, 08:07 AM
i don't doubt that some came with other gearing at all... most i've seen and worked with on the east coast have been packin 1.5 gears.. the math tends to point toward this ratio... as far as rpm and prop pitch.

if the motor is an original 87 it's carbureted and has a quadrajet, fuel injection didn't show up until the a bit before the mid 90's on the smallblocks.

merc has changed hp ratings and gear ratio offerings a lot in the last 15 years... like a little kid who cant make up his mind... sometimes flip flopping year to year. makes it difficult to truly tell. but with considerable experience with the motors of that era my memory recalls the 350 mags being 10 more hp than the 260's. Basically ignition and intake manifold change. but i may very well may be mispoken...

if that motor is truly 300 pshp w/ 1.5 ratio drive he should me turning about 5000 rpm with that 23 pitch assuming everything is in order with that motor...

Serial Numbers may help in deciphering some information.... if you have the black flame arrestor cover it should have a wealth of info on it. including the motor and possibly the sterndrive s/n.

chappy
09-01-2002, 06:07 PM
HEY GUYS, HAD A FRIEND LOOK AT THE OUTDRIVE. RATIO IS 1.5. MOTOR HAS A CARB. HAVEN'T HAD A CHANCE TO RUN THE 21 PITCH CUPPED STAINLESS YET. OUTDRIVE IS AN ALPHA. EVERYONE I TALK TO THINKS THE HP IS 270. JUST A NOTE, THE LAKE I RUN ON IS ONLY 13 MILES LONG. THE DEEPEST CHOP I RUN IS 12 TO 18 INCHES. TWO FEET TOPS. WOULD I BE BETTER OFF WITH THE BOW RISE FROM THE CUPPED 21 PITCH INSTEAD OF THE 23 CLEVER SINCE THEY'RE DESIGNED TO FLATTEN THE HULL IN ROUGH WATER? EITHER WAY, I'VE NEVER DRIVEN A BOAT THAT PERFORMS LIKE THIS, CAN'T BELIEVE IT TOOK ME THIS LONG TO GRAB ONE!!