need for speed

[sunpoke]

Was wondering what the perfect WOT rpm is for a 1989 4cyl mariner magnum. My manuel says 4500-5500.I've got an aluminium Peterbourgh Bass 465.Last year this combination went 26mph at WOT.Boat leaked some and seemed heavy so I tore saturated spray in foam out and repaired haul this spring.Figure I lightened boat up buy 250lbs.Boat still seems to be on the heavy side as it is only 15'5''and 64''at the beam with ply floor and side console w/tilt&trim.This year it still goes 26 mph with normal load.It revs 800 in neutral and 5400 at WOT.Cavatation plate is even with haul.Seems to run along best in normal conditions at 18 mph at 4200rpm.At this rate I'm burning up about 5 gal. in 3 hours.Does this sound about normal for fuel milage.Currently running a 15 pitch prop.Should I try a 17 pitch to decrease my WOT rpm and increase my fuel milage at the lower run rpm's and still maintain my ideal 18 mph.

 

[KCLOST]

Re: need for speed

Shouldn't have a problem, as long as your hole shot is ok now....

 

[KCLOST]

Re: need for speed

Oh, <br /><br />Your fuel mileage sounds right also....<br /><br />Figure 50hp/10 = 5 gallons/hour at WOT

 

[quantumleap]

Re: need for speed

The rpm range you listed is a bit broad. They usually have a 500 wot range not 1000. Check your manual again.

 

[sunpoke]

Re: need for speed

Originally posted by Quantumleap:<br /> The rpm range you listed is a bit broad. They usually have a 500 wot range not 1000. Check your manual again.

Checked manuel again and it list 4500-5500 WOT rpm range which I realize is broad.Would like to know what ideal rpm should technically be.People I've quized around here are varied as some say 5400 and others say 4800. Manuel also states that idle rpm should be 900-1000 in gear.

 

[LubeDude]

Re: need for speed

I think your hole shot is going to suffer if you change pitch. See if you can try an SS, (stainless steel), prop, 13-15. Dont lug your engine, stay on the high side of recomendation.