Prop/Motor Question

[TiredOfWorking]

I have a 2003 Lund 1675 Explorer SS with a 2003 90HP 4 stroke Yamaha. When I initially propped the boat, it hit 6000 rpm and 42mph GPS with 2 people and full tank. I have since added a Minkota PD74US bow mount and two batteries. Now I am getting 5600 rpm and 37.5 mph. Is this normal for the extra weight I have added?

[BIG DS]

Yup. You added about 200lbs to the front of your boat. The prop you have on is just right for the motor now. Outboards should generally run between 5400 and 5800 rpm. The prop you have should be "it". Bofore the addition, you could have jumped up one pitch size. The only thing I would suggest is drilling holes in the hub on the leading edge of the blades. Check with your dealer for the location, size, and if they will do it or know someone that does. That should hepl you pick up a bit of whoat you lost.

[marine_man]

Quote:

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Outboards should generally run between 5400 and 5800 rpm.

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Outboard RPM's are difficult to generalize... most 2 strokes are 5500 rpm.. but some are 5250, and some others are 5750...

Most (not all, but including the 90 HP Yamaha 4 stroke) 4 strokes are supposed to be maxed out at 6,000... not 5800 RPM...

So.. I would change props, but you won't pick your speed up probably unless you were to change to stainless (which is a can of worms for another day)... you will get better hole shot though..

You should be able to go down 2" in pitch (to get the 400 rpm back)...

The one thing I would caution here is that you're running an apples to apples comparison, right (ie - the same number of people in the boat as the 42 mph run)...

marine_man

[TiredOfWorking]

Test conditions are the same. I am not to concerned with top end, (wife panicks at 35 mph) or hole shot, (used for fishing only, no watersports). Both are fine as is. I just wanted to be assured that there was not a problem with the motor. It seems to run perfectly.