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Optimum running RPM, 2000 Honda 90

W

West Wind Dave

New member
My apologies if this has been posted earlier, I looked but couldn't find the info.

My question - I'm looking for the the optimum (safe) running RPM for my Honda 90 (2000). I typically don't run much over 4000 RPMs, but I'm wondering if I can run higher. I have a 22 ft wood dory.

Any input is greatly appreciated!
 
Recommended rev range for your engine is 5000-6000 RPM with max power being produced at 5500. As long as your revs aren`t over 6000 RPM then you`ll be fine.

Matt
 
If you have the owner and service manual in there it says something like for long life don't run motor over 80% or 90% of WOT. Look for it.

The motor and boat will tell you what RPM it likes,my twin 90 boat loves 4600 RPMS and it can run there all day. My fuel flow meters tell me that I like 4200 so it's a struggle.

I wouldn't worry much about blowing up your 90 unless you run it at WOT 24/7.
 
You need to find out if you have the right pitch prop first.
Your wot should be around 5800-6000 rpm.
Only you can find out what the optimum running rpm is. It could be 2500, 3000 rpm. 3500,
who knows ?
 
Agree that you need to get the correct prop - one that will take you to 5800 - 6000 +/- rpm at WOT.

If you have a digital fuel flow meter, you can chart you engine efficiency. Set up a log where you record rpm's, fuel flow in gallons/hour, and GPS speed. Take multiple readings (30 or more) over a range of rpm's. Enter those in an Excel spreadsheet - rpm's in one column and the corresponding GPH in the adjacent column and corresponding MPH in a third adjacent column. Sort the rows based on the rpm's from low to high. From that data use Excel's chart function to produce an X-Y line graph with rpm's on the Y axis and GPH on the X-axis. Smooth the line. The line should show areas where the line has a sharp slope and other areas where it's a flatter slope. Your optimums are at the end of each flatter part of the line, just before it starts flexing steeper. For my 225 on a 25 ft C-Hawk optimum is 4620 rpm at 10.0 GPH. My GPS speed at that RPM is 29.5 MPH.
 
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