Z21 SPEED

[RACER X]

I HAVE A 1988 Z21 WITH A 350MAG. (330HP?)
IT IS A NEW MARINE POWER MOTOR WITH ALUMINUM
HEADS AND INTAKE. EVERYTHING ELCE IS STOCK.
IT HAS A ALPHA ONE WITH A 1.50 RATIO, I AM RUNNING A 19P MIRAGE PROP AND TURNING ABOUT
4600RPM. THE SPEED IS ABOUT 50MPH ON MY GPS.
IS THIS THE BEST I CAN EXPECT?????HELP!!

[wintersux]

Are you sure the engine is putting out that HP? With 330 HP you should need alot more prop or your rev's would be out of sight.
88 z22 owner with 7.4/bravo 330HP runs low 60's.

[RACER X]

WITHOUT DYNO TESTING I CAN ONLY GO BY WHAT THE SPEC. SHEET SAY'S. THE PROP WAS A 21P ORIG. THE MOTOR RUN'S FINE BUT IT DOESN'T FEEL AS FAST AND I JUST GOT THE GPS. THE SPEED ON THE DASH IS A LITTLE SLOWER FROM WHEN I FIRST GOT IT. BUT I CONTRIBUTED THAT TO THE PROP CHANGE.
Originally posted by wintersux:
Are you sure the engine is putting out that HP? With 330 HP you should need alot more prop or your rev's would be out of sight.
88 z22 owner with 7.4/bravo 330HP runs low 60's.

[PaulO]

A Mercruiser 350 mag is 300 propshaft HP. Is the Marine Power motor a new complete motor? EFI? Newly installed? Has it run better before and degraded or is it a new install that you have never been happy with? Last I looked ( a couple of years ago) Marine Power made a Bobtail 350 C.I. motor that was rated at 325 HP at the crank. Either way, it still seems that the RPM is too low. What was the RPM with the 21? Do you know that the 19 is OK?
PaulO

[RACER X]

THE WAY THIS ALL STARTED WAS LAST SUMMER THE MOTOR(350 MARINE POWER)STARTED BLOWING IOL OUT THE DIP STICK AT HIGH RPM'S. DURING THIS TIME FOR SOME REASON I THOUGHT IT SHOULD BE TURNING MORE RPM'S, SO I HAD THE PROP REWORKED FROM 19P TO 21P. AFTER A WHILE I DECEIDED TO FIND OUT WHY IT WAS BLOWING OUT OIL. I FOUND THE THE PISTON HAD BROKE IN THE RING GROOVES. AT THAT TIME I REBUILT THE ENGIN WITH THE SAME TYPE PISTONS ONLY .20 OVER. EVERYTHING REMAINED THE SAME EXCEPT I ADDED A FRESH WATER COOLING SYSTEM WHICH RAISED THE TEMP. FROM ABOUT 105 TO 160 AT W.O.T.. THE MOTOR HAS A STOCK CARB. I HAVE PUT ABOUT 13HRS. SINCE THE REBUILD BUT IT WAS NOT BUILT TIGHT. P.S. IT DOSN'T BLOW OIL ANYMORE!!
Originally posted by PaulO:
A Mercruiser 350 mag is 300 propshaft HP. Is the Marine Power motor a new complete motor? EFI? Newly installed? Has it run better before and degraded or is it a new install that you have never been happy with? Last I looked ( a couple of years ago) Marine Power made a Bobtail 350 C.I. motor that was rated at 325 HP at the crank. Either way, it still seems that the RPM is too low. What was the RPM with the 21? Do you know that the 19 is OK?
PaulO

[PaulO]

My tired 260 (classic 18) would turn a 21 Mirage to 4700 and into the low 60s. I expect that a Z21 would have a faster hull and the difference in length would be a wash or, in your favor. Therefore, I believe you are right and that the motor is not producing the power it should or, there are other more unlikely problems. Did you perform the basics such as total ignition timing, throttle plates opening all the way, clean flame arrestor? Does the engine seem to run well? Does it exhibit any symptoms of fuel starvation or lean carburetion? Is there proper airflow into the engine compartment? Is there a hideous thick green growth on the hull? (just kidding).
PaulO

[RACER X]

No thick green growth, just a couple of anchors behind me. I have not rechecked the timing since I put it in but I will this weekend. also I need to make sure of the max rmp at w.o.t.. It may be higher than I stated before and the loss in speed may be due to the prop pitch change?
Originally posted by PaulO:
My tired 260 (classic 18) would turn a 21 Mirage to 4700 and into the low 60s. I expect that a Z21 would have a faster hull and the difference in length would be a wash or, in your favor. Therefore, I believe you are right and that the motor is not producing the power it should or, there are other more unlikely problems. Did you perform the basics such as total ignition timing, throttle plates opening all the way, clean flame arrestor? Does the engine seem to run well? Does it exhibit any symptoms of fuel starvation or lean carburetion? Is there proper airflow into the engine compartment? Is there a hideous thick green growth on the hull? (just kidding).
PaulO

[RACER X]

How can I post pictures of my boat without having a home page?

[OceanCommotion]

you really can't. you need to have uploaded them into a directory somewhere on the web. If you have pictures that you could email me, I'b be happy to put a few of them up in one of my directories.

Jay

jay_fraga@applimetrix.com

[RACER X]

WILL THEY BE REFERENCED ON THE REGISTRY'S PAGE? WHERE CAN I SEND THEM TO YOU?
Originally posted by OceanCommotion:
you really can't. you need to have uploaded them into a directory somewhere on the web. If you have pictures that you could email me, I'b be happy to put a few of them up in one of my directories.

Jay

jay_fraga@applimetrix.com

[OceanCommotion]

Harbormaster may have webspace to put them into the registry on, but if not- send them to me (email) at jay_fraga@applimetrix.com .

From there, I'd give you the URL (address) so that you could link them from anywhere, including the registry.

[harbormaster]

Hey RACERX?

have you even read the blurb at the top of the boat registry page??

Its says that you can email me the electronic photos or us mail the photos to me and I will scan them in and post them.
If you want the photos back yu will need to send return postage.

Scot

[OceanCommotion]

He probably didn't, Scot-

they're online if anyone's interested.

here: http://www.applimetrix.com/users/elamulle/

[GEOO]

RacerX, My 1975 18 Donzi ran 58 mph with a 300hp and a Volvo 290 drive. Your 21 footer is much bigger and heavier. 50 mph might not be far off for your top speed. Great photo's !! You have a nice size cabin. Boat looks to be in mint condition. Good Luck with her. GEOO

[EricG]

I must first apologize, not all of the number keys are working on the laptop........

My 88 Z21 with the stock three fifty Magnum (270 HP), runs a similar speed to yours with a 20 pitch Cleaver at forty five hundred RPM.
Which tells me that your engine probably isn't much more than stock as far as output.

I read a 1987 Popular mechanics review of our boats, running the same setup as mine, and they said that they experimented with props in order to sqeeze all the top end the could find (it was a comparison article). They got a radar speed of fifty six and change with this setup, but they unfortunately didn't go into the specifics of the prop. Based on that, I plan on doing some prop experimenting myself to see if I can get more. All I really want now is to get my speedo over sixty, it's at fifty nine now. Then at least I can pretend...

Just my two cents.

EG


[This message has been edited by EricG (edited 09-04-2000).]

[RACER X]

I have solved the mystery! I have several props that look alike and I was running a 23p cleaver insted of the 19p.cleaver after changing the prop it turns 5200 at w.o.t. and runs 58 with 4 people and a full tank of gas. I am now confident it is running like it should thanks for everyones good suggestions.
Originally posted by EricG:
I must first apologize, not all of the number keys are working on the laptop........

My 88 Z21 with the stock three fifty Magnum (270 HP), runs a similar speed to yours with a 20 pitch Cleaver at forty five hundred RPM.
Which tells me that your engine probably isn't much more than stock as far as output.

I read a 1987 Popular mechanics review of our boats, running the same setup as mine, and they said that they experimented with props in order to sqeeze all the top end the could find (it was a comparison article). They got a radar speed of fifty six and change with this setup, but they unfortunately didn't go into the specifics of the prop. Based on that, I plan on doing some prop experimenting myself to see if I can get more. All I really want now is to get my speedo over sixty, it's at fifty nine now. Then at least I can pretend...

Just my two cents.

EG


[This message has been edited by EricG (edited 09-04-2000).]

[EricG]

I'm very glad to hear you found the problem, I was getting very worried about the possiblity of not getting any more speed out of mine....at least you've given me hope.

Good luck with the Z29 Hunt!!

EG

[jamieZ]

My Donzi Z21 with the 270HP Mag runs about 50MPH with a 19inch prop at about 4600RPM. That's about right.People who say there boats run 10MPH faster with basically the same setup are dreaming in Technicolour...