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Redline for 1978 merc 228

matt288

matt288

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"Was curious if anyone knows w

"Was curious if anyone knows what the max rpm for a '78 228 gm 305 is? She does about 35mph at @ 4000 rpms, would like to know how I can make her faster. I know a prop would probably make a difference. Am currently running a 48 78122 A40 21P, don't know what it means but its stamped on the prop. Thanks all"
 
"Ayuh,... WOT rpms should be

"Ayuh,... WOT rpms should be 4400/ 4800....

Before you buy another prop,... Has the motor been Tuned Up,+ Serviced lately,..??
Your prop is a 21" pitch,...
19" is the next smaller...."
 
"thanks for the info Bondo, I

"thanks for the info Bondo, I won't be going with another prop anytime soon, thats just a thought, I'm not sure the last time the boat was serviced, just bought it a month ago.
Is it just plugs , cap, rotor, wires, and filters? much like a car?"
 
"how big of a boat is this 305

"how big of a boat is this 305 pushing? Is it a 2bbl or 4bbl carb?

My friend I grew up with at the Lake had a 1978 or 1979 20' IMP ( tank basically ) with a 305 with a 4bbl in it, not sure what pitch it was but it would turn around 47 to 4800 rpms and run around 47mph, it had to run in the low 40s trying to drag my hiney barefoot. Your boat will definately run a little faster it sounds like if you get the right prop as it is only turning 4000rpms. Like Bondo said a 19 will get you more rpms but before i went that route, i would give it a tune up."
 
"[b]"I won't be going

""I won't be going with another prop anytime soon, thats just a thought,"

Ayuh,... You gotta do Something,...
You're Lugging the motor at only 4000rpms..."
 
"Tahnks all, the motor revs up

"Tahnks all, the motor revs up past 5000 rpms, I just haven't gone that high cause I wasn't sure what my redline was.
The boat is a 20' 1978 Slickraft cuddy, not bad, feels heavy on the trailer, so I guess that little prop is pushing a lot of weight."
 
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