How to get more HP from a Mercruiser 470?

Question

I have a 1982/83 vintage Mercruiser 470 in a 17 foot Formula (Formula One Runabout). I need a better hole shot for Water Ski purposes. Is there any modification I can make to this Engine to get more HP and more importantly, a better shot out of the hole? Also, are there any suggestions that I can do in terms of propellers and trim tabs that may improve the hole shot of the boat?

At present, the boat has a 3 blade 14 X 19 (pitch) prop that at WOT allows the engine to run up to 5000 rpm.

Answer 1

you can improve hole shot by venting your prop

write-up and instructions with diagram:

http://forums.iboats.com/showthread.php?...

Answer 2

This is an interesting question.  The standard 470 had a two barrel carburetor.  There is such a thing as a four barrel carb. that you need a different manifold adapter plate, and there is a throttle cable bracket that you need, but It been nearly 20 years since I did the conversion.  But, If you could find an old boat with this 4 barrel carb in it, you might be able to get the whole rig for say $1500. Then rebuild the best engine.... and use the other for parts.   I think it was about 1992 that I did this, and the engine was listed as a MC 190.    

        There has always been a problem with what engine to use in these boats.  The 4 cly is just a little to small, and the V-8 is to heavy.  The V-6 in this era had to flat a power curve.  Perhaps the real solution is to find a used 21' with V-8 power. I've seen some on ebay for $3-4 thousand.

Answer 3

Only two things I can think of is thru hull exaust and drop the pitch one inch

Answer 4

Go to a 4 blade prop.  This will give you a better hole shot, but less top end .  My guess is that you would want an alpha 4, 14X18