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View Full Version : boiled my 383 again HELP PLEASE



lee
07-18-2008, 10:21 PM
i have a classic 18 1981 with a alpha drive boat runs perfect 3k-4k temp barely moves but as soon as i go WOT 5200 RPMS ENGINE TEMP CLIMBS SO FAST IT PEGS TEMP IN LESS THAN 1.5 MINUTES OF RUNNING TIME. IS THE PUMP IN THE DRIVE NOT BIG ENOUGH FOR MY 400 HP ENGINE OR COULD THERE POSSIBLY BE A OLD PICE OF EMPELLER IN MY DRIVE. WHEN I PURCHASED I PUT A NEW ONE IN ,OLD ONE WAS NOT TO BAD BUT I'VE ALWAYS HAD THIS PROBLEM I WILL BE INSTALLING A ALARM ON IT THIS TIME FOR SURE AND A KILL SWITCH WHILE I'M TEARING THE HEAD OFF WILL BE TEARING THE PORT HEAD OFF AND HAVE IT CHECKED CHECKED ON MONDAY TO SEE IF I DID ANY EXTRA DAMMAGE HAS A LASER PROP PITCH 19 AND ALPHA DRIVE IS 1.5 RATIO

MOP
07-18-2008, 10:54 PM
Check pump flow and the power steering oil cooler for debris.

kramsay1234
07-19-2008, 12:17 AM
There is no problem with 400hp and an Alpha. I had that combo with my Alpha and my 400 sb with about the same hp and no problems with running temps at all. Definitely something else going on there...

MOP
07-19-2008, 07:32 AM
Your numbers don't jive! 383-400HP swinging a 19" wheel on a 1.5 Alpha would be spinning some very high RPM's. My 22 with a mild 383 swings a 23" 4 blade to 5,100. When you get the heads off measure the bore & stroke, you may have been sold a bill of goods!

onesubdrvr
07-19-2008, 08:55 AM
Just as a side note, check the timing too, it can cause heat problems, and definitely power problems.

Wayne

MOP
07-19-2008, 10:33 AM
Like Wayne says check your timing, wind it up to about 3000 that will give you your top time which should be 32-34. You should if the engine is what it is reported to be swing a 24-25" prop up about 5000, something is way off hopefully just the timing!

BigGrizzly
07-19-2008, 10:37 AM
Like MOP says theres something wrong with the numbers. If you are swing a 19 pitch at 5200 with a 383 and an 18 boat it will run hot. just tow your boat in first or second at 4000 and watch your temp gage. What ignition do you have. what is the total advance?

GeneD
07-19-2008, 05:29 PM
Everyone has great ideas on where to check on the root of this problem.
Check 'em all.
One thing I would like to add is to check the thermostat.
You should be running a 142 degree, and it almost sounds like you're not running one at all.
I had the same problem with my 406, and my partner claimed it was normal oil heat build up.
Of course, your impeller could be shot too. And overheating can cause the water pump housing to warp (sucking air or blowing water), sometimes just an impeller replacement won't do the trick.

Rootsy
07-21-2008, 08:20 AM
When was the last time you replaced the impeller in the drive? Once a year is a good interval. Lack of coolant flow is the culprit in this case IMO, either from a weak impeller, missing veins or blocked oil cooler (if so equipped) with pieces of impeller or other debris.