WOT Issue...Maybe?

[badrano]

Just checking out the posts and saw one under the Prop section where the boat owner was hitting 3000rpms and ~30mph.

Ironically, over the weekend I went WOT since the water was super smooth and hit ~3800 rpms, but my SOG was 37+ kts.

When I bought the boat, the surveyor noted 41mph (GPS) at 4400 rpms even though the one pic he had showed his phone indicating 40mph with the tach in the background at 4100. At the time of the survey, it was just him and the driver.

This past weekend it was the whole family (2 adults 2 kids). I'm wondering if I need to go through the WOT checklist from the sticky?

One other thought is that I may have had a little bit of current pushing me along.

 

[alldodge]

Ironically, over the weekend I went WOT since the water was super smooth and hit ~3800 rpms, but my SOG was 37+ kts.

Need a bit of clarification, 37 knots = 42 mph

If that is correct then wonder if there is a tachometer issue

 

[Scott Danforth]

if you are only hitting 3800 RPM at WOT, with the motor trimmed, then yes, go thru the low WOT checklist

start with the tach
look at prop pitch (should be about a 15x19p 3-blade for that combo)

 

[badrano]

if you are only hitting 3800 RPM at WOT, with the motor trimmed, then yes, go thru the low WOT checklist

start with the tach
look at prop pitch (should be about a 15x19p 3-blade for that combo)

I got to stop having these senior moments. I have a 4 blade prop...not sure what the pitch is.

I'll have to go out on another smooth day and try some of the boat configuration items before I start tearing in to the engine.

 

[Scott Danforth]

you will need to know pitch prior to going any further.

 

[QBhoy]

Play with the trim. Lots of variants to think about too. Tide and load on the boat.
But try trimming first. My boat will seriously vary in performance and rpm trim down to trim up. Difference of about 10 mph easy on mine.