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Nissan 15hp lack of power

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Matt04

Member
I posted a previous thread on here about my Nissan Ns15d2, bogging down under load; www.marineengine.com/boat-forum/showthread.php?423809-15hp-bogging-down-and-dieing-under-load
I think I have fixed that problem, and the motor runs very smoothly now, but my problem is it doesn't have much power, it only has about as much or a little less power than my 86 evinrude 9.9 hp outboard. In the previous thread it was mentioned that I could have the wrong prop, I measured my prop today it looks like it is a 9×8.3 does this seem like the right size for that motor on a 11'2" Zodiac type inflatable boat? The boat weighs about 150lbs and I usually have 2-4 people in it plus gear. Right now it barely gets on plan with two people and gear. I also bought a tachometer and I will report back after I take the boat out with the tach.
 
I got the boat out in the lake today with the tachometer, wot with just me in the boat, glassy water, was 5050-5100rpm with me and another person in the boat it was 4900-4950 rpms. I guess that means I need a different prop? Anyone have any suggestions on what prop to get? I want to use the boat for diving and might have it pretty loaded down with gear and people sometimes, getting up on plane with it loaded down is more important to me than top speed. Also does anyone have any suggestions for a website that sells new or used props for reasonable prices, if I do need a prop.
Thank you guys for all the help so far, it has really helped me out.
Edited to add the factory service manual says max rpm for this engine should be 5500-5800
 
You can go up to 5800, so reduce pitch a couple of inches. Figure rule of thumb 300 rpm/inch. Go with new to get a good rubber hub.
 
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