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Discussion Starter · #1 ·
i have a 85 22' avanti with a 5.7 mercury it seams to top out at 50 mph. the rpms are only at 3000 i am new to boats but i know a 350 chevy revs higher than this. should i be getting more rpms out of this engine or is this all it has. also the engine is in very good shape and the boat only has 500 hours on it and i did a tune up and an oil change too it before i took it out. any info anyone could give me would really help me out
 
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i have a 85 22' avanti with a 5.7 mercury it seams to top out at 50 mph. the rpms are only at 3000 i am new to boats but i know a 350 chevy revs higher than this. should i be getting more rpms out of this engine or is this all it has. also the engine is in very good shape and the boat only has 500 hours on it and i did a tune up and an oil change too it before i took it out. any info anyone could give me would really help me out
50 MPH at 3000 RPM's doesn't sound right. I would bet the either the speedo or tach is way off.
 

· LHC Architect
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i have a 85 22' avanti with a 5.7 mercury it seams to top out at 50 mph. the rpms are only at 3000 i am new to boats but i know a 350 chevy revs higher than this. should i be getting more rpms out of this engine or is this all it has. also the engine is in very good shape and the boat only has 500 hours on it and i did a tune up and an oil change too it before i took it out. any info anyone could give me would really help me out
:)sphss
thats one tired 350;)
 

· E-7 Sheepdog (ret)
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i have a 85 22' avanti with a 5.7 mercury it seams to top out at 50 mph. the rpms are only at 3000 i am new to boats but i know a 350 chevy revs higher than this. should i be getting more rpms out of this engine or is this all it has. also the engine is in very good shape and the boat only has 500 hours on it and i did a tune up and an oil change too it before i took it out. any info anyone could give me would really help me out
Your "correct" RPM should be in the 5,000RPM ballpark.

First make sure your tachometer isn't lying to you.
Compare it to a good tach, someone's dwell/tach, a spare known good tach a friend will loan you, etc. Make sure the 3,000RPM is good information.

Next, exactly what size and pitch prop is on it?
Does it get on plane reasonably, or is it plowing allong like an ocean liner @ 3-grand?

If it is running smoothly (you do not say), just not winding up, I do not suspect mis-wired from a tune-up.
If you gave it a tune-up, make sure it is getting timing advance. Should be something on the order of 8-10* at idle, 35* ballpark at/by 3,000rpm. If the advance is stuck imobile, you will loose a LOT of top end power.

If the above checks OK, carbureted or fuel injected? If carbed, what carb? Insure the seccondaries (if equipped with a 4-barrel) are opening under full power. If it is a load-type carb (like a quadrajet or an Edelbrock version of a Q-jet), it may not pull the air flaps open @ 3,000, but they should be free, not stuck, jammed, etc. and the lower butterflies should open when the linkage is wide open.

Insure you actually get wide open on the throttle when you call for wide open from the helm, cable adjustment there.

good luck.
 

· I'm baaaaack...
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65 or so if it's in a Cheetah on a cool day with no passengers. On a warm day with 6 or 8 people it should still go almost 60.
 
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