500 RPM

[TeeKay]

So I finally bought a new prop for my '94 21Se with a same year 150 yamaha. It previously had a 11 pitch 3 blade and I went to the enertia 15 pitch. What a world of difference!! My only question now is, is 500 RPM too far off the max RPM? It is rated to spin 5500, regularly gets 5000 and flirts with 5100. Do i have anything to worry about?

Thanks,
Tom

 

[tomysel]

How are you loaded??? You should load your boat like how it gets used.. 2-4 people, fishing gear, ice, food, 2/3 fuel and u shouldn't be off by more then 200rpm..

 

[DaleH]

Ideally you'd want it 200 off, no more than 300 off. Typically tested with 1/3rd fuel and all the gear typically carried. A good prop shop should be able to tweak the wheel to give you a few more hundred RPMs. But check your motor height first, as if too low, raising it usually adds a few hundred too.

 

[TomS]

At this point I would only focus on the prop if I knew that motor itself was in perfect running condition.. in other words, make sure all your engine maintenance has been done, especially in all areas of the fuel system - pumps, screens, injectors, etc.. A collection of small things could easily drop a couple of hundred RPM, especially on a 9 year old motor.

-- Tom

 

[tomysel]

What were you running with the 11 pitch that you decided to switch to a 15 pitch? That's a big difference... Usually people go 1or 2 pitch difference..

 

[TeeKay]

Thank you for the replies.

I was running with myself and one other person with about 80 gallons of fuel so it was just about how typically run my boat weight wise. (usually fish alone)

I know for a fact the my motor is mounted too deep. I would like to raise it one hole but the way it was mounted from the factory will not allow it to be raised. the two bolts on the bottom slot are as low as they can be drilled and mounted. It is a bit much for me to have new holes drilled and the old ones plugged on a college student salary and schedule at the moment.

The engine is in very good condition and runs like a champ. The previous owners did not get much use out of the boat and before buying the boat, a mechanic had thoroughly gone through the engine and gave it the thumbs up.

The previous prop (11 pitch 3 blade) would spin up to 6000 RPM and after doing a lot of digging i finally figured out that 5500 RPM is max for my 94 outboard. Ken at propgods also recommended the enertia 15. Went from 6000 WOT @ 28kts to 5000 WOT @ 33kts. I was mostly concerned with the mid range performance however and have also seen a huge gain.

-Tom

 

[TeeKay]

One thing i forgot to mention is the fact that my boat also has a 55 gallon bait tank and when that is full my engine gets 4900 rpm. I usually run that half full but filled it up just for kicks to run with the new prop.

-Tom