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View Full Version : 260 SHAFT HP? IN 1984?=CRAZY



SShammy
03-18-2003, 08:50 AM
WILL SOMEONE WITHT A LITTLE MECHANICAL APPTITUDE EXPLAIN TO ME HOW IN THE HECK YOU GET 260 HORSEPOWER OUT OF 5.7 MERCRUISER WAS USING IN 1984.IT SEEMS TO BE A BOGUN NUMBER FOR NO OTHER REASON THAN THE RESTRICTIVE AIR CLEANERS, THE EXHAUST BACK PRESSURE, LACK OF CAM SHAFT AND POOR FLOWING HEADS. OR MAYBE MERCRUISER PUT SOME GOOD HEADSA ON THEM? DOES ANY ONE KNOW? ALL I KNOW IS THAT A 1985 350 Was a gutlss wonder in comparison to say a late model vortec engine that produces 255 horsepower.Did mercruiser have the engine rigged with goodies or are they just full of it?

DUCKY
03-19-2003, 10:13 PM
Mercruiser used a larger cam, installed "straight-up" as opposed to retarded and the marine manifolds flow better. Along with a more agressive tune-up, and fewer parasitic accessories. Not to mention the fact that do you really think that a 350 Chevy ever REALLY only put out 160hp (as advertised in the 1984 Camaro)? That was all a smoke and mirrors game with emissions and the insurance industry and the government.

SShammy
03-20-2003, 06:45 AM
HEY DUCKY THASNKS FOR THE INPUT. I TALKED TO MERCRUISER AND THEY TOLD ME THAT THOSE MOTORS WHERE RATED AT THE FLYWHEEL NOT THE PROP SHAFT. WHICH IS MUCH MORE BELEIVABLE. ITS NOT HARD TO MAKE 260 HP AT THE FLYWHEEL WITH A BASICALLY STOCK MOTOR BUT IT IS ANOTHER THING ALL TOGETHER TO DO THAT AT THE PROPSHAFT WITH A Basically stock motor because the heads they used just didnt flow that good. guy at mercruikser also told me that that 260 at the flywhyeel was on a good day and may be a little generous for the actual units that were sittign in most boats.

77charger
03-21-2003, 04:45 PM
I was lookin at an older hot boat article on a boat that had a 350 mag(1993)It stated 250 at the prop sounds close to me cause i have heard 270(didnt know if from the motor or the prop)

DUCKY
03-21-2003, 08:51 PM
I thought the BIA/NMMA nipped the HP ratings from the crank in the butt in the late 70's. Maybe that was just for the outboards.....

SShammy
03-23-2003, 05:32 AM
I thought so tooo ducky but the guys up at mercruiser told me other wise.

Skullinator
03-24-2003, 07:31 PM
:) :) :)