exhaust trouble/tachometer

rolmops

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Joined
Feb 24, 2002
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This is for a 1984 4 cylinder 75 horse Mercury outboard,which I picked up with a 1984 18 foot sylvan for $1000 bucks.This is my second Merc,all my other outboards are OMC
This engine has a through hub exhaust system, which should dull the noise and leave very little smoke to come out of the ports on the exhaust extension plate.
There is a quite a bit of smoke and noise coming out of these ports and I wonder what, if anything can be done about this.
My other question is about the correctness of the tachometer.At WOT it reads 6500 which is probably to high for this engine.How trustworthy are mercury tachometers?Or is it time to increase propeller pitch by 5 numbers?
The boat is rated for 140 horse and with only 75 it does about 30 knots on flat water which for a fishing rig is fine.
Thank you for all answers and opinions.
 
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