Cam and speed question: Merc 370 HP-454 in Scarab III 34'
03-15-2004, 07:43 PM
#11
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Originally posted by formula31
The cam specs in my book (90-14499--1 887) are wrong and meaningless for "advertised" duration. Their "note" references are wrong too. While that cam does seem small, be careful going too big . That boat is heavy and needs torque.
The cam specs in my book (90-14499--1 887) are wrong and meaningless for "advertised" duration. Their "note" references are wrong too. While that cam does seem small, be careful going too big . That boat is heavy and needs torque.
Anyway, things are getting clear. I have exactly the same book as you (90-14499--1 887)
Thanks for making sense to this.
03-15-2004, 07:46 PM
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Originally posted by blue thunder
I have often thought it would be a great value added feature if OSO would put together a concise factual database of specs on all popular production engines. They could also add to it a section on 330 on roids specs. It would really answer a lot of conflicting data.
BT
I have often thought it would be a great value added feature if OSO would put together a concise factual database of specs on all popular production engines. They could also add to it a section on 330 on roids specs. It would really answer a lot of conflicting data.
BT
03-15-2004, 09:01 PM
#13
Thanks for the specs. We looked in the Crane book and saw that cam, but it says for free flowing exhaust. Not sure what that means, but I don't think the log manifolds cut it. There is a cam for 350 HP that has 222 duration and 529 lift, says for use with standard exhaust. Is there a concern about reversion here?
The cam above is definitely more than what was put in the engine at the last rebuild. We don't want to go too far and lose low RPM torque. This is a big, heavy boat.
Anybody with a similar boat/engine combo that can tell us what speed and prop we should be running?
The cam above is definitely more than what was put in the engine at the last rebuild. We don't want to go too far and lose low RPM torque. This is a big, heavy boat.
Anybody with a similar boat/engine combo that can tell us what speed and prop we should be running?
03-15-2004, 09:28 PM
#14
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I had 400 Cyclones in a 40 ft Scarab 400. With a little fuel the boat weighed 11,000. They pushed the boat to almost 60 mph. I also had a pair of 420's in a 30 ft Scarab. It went 72mph. Both boats had the log manifolds. Don't worry about the torque or water reversion. Just make sure to prop it to spin 5000.
03-16-2004, 07:54 AM
#16
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Can't be a 400/420 cause they came with Crane Gold's and you said they were added at rebuild.
Cam sounds way offbase.
recto port heads make me guess a 370, like you already determined, but the cam is not original for sure.
Cam sounds way offbase.
recto port heads make me guess a 370, like you already determined, but the cam is not original for sure.
03-16-2004, 08:56 AM
#17
What's bothering me is, did the original owner put in the small cams to save some money on rebuilding the engines just prior to sale, or did somebody think they were necessary to get the boat up and moving? I don't want to recommend too much cam to my friend.
Yes, I already suggested that superchargers would take care of everything but they're out of his budget.
Yes, I already suggested that superchargers would take care of everything but they're out of his budget.
03-16-2004, 10:57 AM
#18
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My guess is that somebody who didn't know what they were doing put those cams in your friends boat. You said he couldn't spin 19 pitch props to 5000. My 40, weighing 2500 lbs more, would spin 21 Hydromotives to 5000. I did ,in addition, add MSD ignition, to replace the points ignition that was there.
03-16-2004, 12:50 PM
#20
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I WORKED AT CUSTOM ENGINE SERVICE BACK IN THE 80S WE WERE ONE OF FEW MERC DEALERS BACK THE AND WE USE TO CONVERT THE 370S TO 400S BY CHANGING THE CAMS TO THE CS1139 SEALED POWER CAM AND CHANGE THE ROCKERS FROM STAMPED STEEL TO THE CRANES AND REPLACE THE VALVE COVERS WITH THE CP CAST ONES FOR CLEARANCE THE 370 CAM WAS A 214/214 .501/.501 AND THE 400 WAS 224/232 .527/.553 THE 370S MADE342 TO 349 HP AND THE 400 MADE 372 TO 378 HP IF YOU WANT TO PICK UP THE POWER USE SOME EXHAUST ELBOWS WITH MORE SWEEP WE SAW AS MUCH AS 25 TO 30 HP ON THE EXHAUST ALONE. WE DID THIS SAME CONVERSION ON A BOAT FOR DON JOHNSON FROM MIAMI VICE BACK THEN . HOPE THIS INFO WILL HELP YOU. IF YOUHAVE ANY OTHRE QUESTIONS FEEL FREE TO CALL 1-305-884-5368 LAZ MESA
