Max horsepower

[1224bret]

Just been lacking some motivation but hopefully will be testing it out the weekend after thanksgiving!

[fixit]

my 91 v20 is running a 300hp mpi small block with a bravo leg in mine.
i turn a 18" mariage plus prop and my WOT is 5200
really stern heavy and had to put tabs on it to stop it from porposing

its a heavy boat with all the downriggers, radar arch/rod holders, 6" full canvas top, stereo, 9.9 kicker, dual batterys, prawn puller with traps etc etc etc

my max speed is around 42 knots, but cruises ar 30knots at 3200 rpm getting 2.5mpg according to the smartcraft gauges. jumps up on a plane in 2-3 seconds. i could have saved some weight and probably gained top end with an alpha leg but found a complete bravo package instead

[RidgeRunner]

I don't see how you could be any more stern heavy than my rig. But mine does not porpoise at normal trim angles. If you over trim without the hammer down, yes it will porpoise. I haven't seen one yet that wouldn't if you put in too much trim.. MY .02

[spareparts]

Originally Posted by RidgeRunner

I don't see how you could be any more stern heavy than my rig. But mine does not porpoise at normal trim angles. If you over trim without the hammer down, yes it will porpoise. I haven't seen one yet that wouldn't if you put in too much trim.. MY .02

I/O Bravo, way heavy

[spareparts]

Originally Posted by fixit

my 91 v20 is running a 300hp mpi small block with a bravo leg in mine.
i turn a 18" mariage plus prop and my WOT is 5200
really stern heavy and had to put tabs on it to stop it from porposing

its a heavy boat with all the downriggers, radar arch/rod holders, 6" full canvas top, stereo, 9.9 kicker, dual batterys, prawn puller with traps etc etc etc

my max speed is around 42 knots, but cruises ar 30knots at 3200 rpm getting 2.5mpg according to the smartcraft gauges. jumps up on a plane in 2-3 seconds. i could have saved some weight and probably gained top end with an alpha leg but found a complete bravo package instead

you need a higher pitch prop, bring it down to around 4800-4900 at WOT

[fixit]

Originally Posted by spareparts

you need a higher pitch prop, bring it down to around 4800-4900 at WOT

4800-5200 is the normal wot operating range for an mpi motor. its actually 5170rpm when its stripped down and empty of fuel/light, and 4900 when loaded up with gear and fuel. --- just perfect imo

fyi the bottom of my swim platform sits about flush with the water

[THEFERMANATOR]

Speaking from experience, if its an injected engine, it starts pulling power at 4900 or so. Put one in a few years back, and found it to be PICKY about propping. If you went a hair low on pitch, it would pull power, a hair to much pitch and it would bog out, but get it JUST right and she would boogy.

[Destroyer]

The real problem with propping is that there's so much more to a prop than just the pitch, and all of them effect how the engine preforms. You have pitch, diameter, rake, cupping, prop material, type of blade, blade tip, number of blades, and of course, position of the blade in the water, just to name a few. (there are more) And each and every one of those items can and will effect the overall performance of the engine and the boat.

[spareparts]

Originally Posted by fixit

4800-5200 is the normal wot operating range for an mpi motor. its actually 5170rpm when its stripped down and empty of fuel/light, and 4900 when loaded up with gear and fuel. --- just perfect imo

fyi the bottom of my swim platform sits about flush with the water

nope, its 4800-5000, just put a brand new 350 MPI in a boat today, its got the rpm written on the cover. Ferm is correct, that motor starts pulling power at 4900, I like to prop them out so they run 4800 at a light load, WOT

[fixit]

straight from mercurys website
4800-5200 rpm

https://www.mercurymarine.com/en/ca/...specifications