What RPM is abuse?

[Tucker]

Gents,
RE: 150 OX66.
At what RPM is best? Geeeez there are so many opinions about this. Some guys say these 2-strokes can be run wide open all day (finding that hard to believe). Just looking for best (fastest) transit time without blowing the thing up. Been running between 4100 & 4400 and was hoping to push it a little harder.

[robert graham]

Most of the modern motors are set up for 4500 to 5500RPM's, lots of folks, myself included, run 5800 with no apparent damage, some motors have rev limiters set for around 6200. I usually run in the 3500 to 4500 range because of fuel efficiency is better, at 5500 the motors are really sucking the gas with only a few more MPH to show for it and I don't like to feel like I'm just "running the guts out of it", but that's just the old man talkin'. Good Luck!

[Tucker]

Thanks Robert,
I max out at 5100 RPM and at that RPM she's singing, not yelling. I've done this for 5-10 minutes at a time and she sounds great and shows no ill effect. I'm just afraid the thing is going to grenade.

[jb123]

mine humm the best at 4400but i also have run them at 5500 for 4 hrs straight, in the dark at that ! damaging i would say is 6k and over, at that rate it really wears out wrist bearings quickly.

[robert graham]

Check: Yamaha outboard performance bulletins for your boat/motor combination for best MPG, MPH, GPH,for any given RPM. Unless you're just into speed then above 5000RPM's you're just burning a lot of gas. And hey, you're on the lake/river to fish and relax, so what's the hurry? Old man talkin' again. Good Luck!

[rbodine]

You are running way to much prop if you are only getting 5100 rpms out of it, you should at WOT be in the upper 5k. Motor guys will warn you about only getting 5100 out of a motor, you are basically lugging the engine.

[robert graham]

Odds are at 5100 he could trim it out a bit more to get more of the hull out of the water and pick up another few hondred RPM's. If I trim my jon boat out for 5500RPM then it gets unstable and starts porpoising, hull's just not made for that. About 5200 is best max for my rig and I usually run in the 2500 to 4500 range. Good Luck!

[Tucker]

Ok maybe I'm running too much prop, but the manual says the range is 4500-5500, so I'm right in the middle right. Am I still over proped if I'm within the recommended RPM range?

[rbodine]

I think the thing is cleaning out, carbon build up etc. If you dont ever run it in the top end of the rpm range it is going to eventually load up with carbon build up..I am not a mechanic at all, so this is just my opinion from what Ive heard!! But you are exactly right, ask, 8 people, get 8 answers.. But I used to turn my vmax 150,up to 6k and it is still running great all over the keys with the new owner today. My ox66 250 I turn up to 6k WOT and it is stil going strong. I notice that at around 5700, it seems as though it is barely working! Good luck with all this, maybe we will both learn something.

[rbodine]

One thing I just thought of, when I was testing props, techs told me that at WOT and trimmed out I should be able to atleast reach the top of the recommended RPM range, so if you cant reach 5500 atleast than you have too much prop!!

[blazen cajun]

I had an Yamaha 85 for 16 years that was run wot or idle. Never had a wrench touch it except to change plugs and lower unit oil. It would turn 5600 and that is where it stayed. When we were kids we all had Tiller motors and that is how we ran them too. I do use yamalube, ring free and name brand gas. I don't know if it made a difference but you can't argue with getting that amount of usage out of a motor.

[seapro21]

i have a 21ft seapro with a 2001 ox 66 200.went to a 17ss prop and now turn 5500 wot with normal gear and 2 people on flat water which tops out about 38mph trimmed before purposing.with the standard 19m prop i topped out at 5100rpm.i fish in the deleware bay which is not flat very often,normally a tight chop and normally 2-4 waves.which means i normally run 4000rpm at 25mph which also gives best fuel economy running 87 octane .i used to run wot for the last 5 minutes in to blow out the carbon,but was told by several certified mechanics, i was just wasting gas.right now the motor has 700hrs on it and other then winterizing it,and water pumps,i have done nothing else to it.i use ring free faithfully and yamalube.they say these motors are bullet proof and will last forever,and i am hoping that is true.

[tunnels]

Sounds like you need to check you motor height set up first and make sure thats right ! if you cant reach full rpms 6100 that the limiter in the computer is set for with just one person and a empty boat , it need reproping down to beable to reach that figure . the motor is laboring basicly because it over loaded . All boats have a sweet spot ! with my 115 V4 it around 3000 to 3500 where the motor is purring and quiet and the boat is performing at its best and most efficent speed . I can cruise for hours at this speed with no problems . push the throttle and it will go to 6100 and thats really going for it . Dont know what speed because its off the clock and hard round !
Wish Yamaha speedo's went to a highter speed reading !!
If you are porposing you are not trimmed properly !! need to come down a little !!
To find your best trim you need to start off and get onto the plane at say 3500rpms on the dot, then gradually trim up from the down possition and watch the revcounter and listen to the sound of the motor it will tell you where your optimum trim angle is as the motor will pick up a few more revs and the boat will feel good and gain a little more speed . Take particular note on the trim gauge of that possition because thats your sweet spot for your boat as it is loaded at the time and for the conditions !!
My motor picks up about 100 rpms when the trim is set for the load i have at that time and you can hear the change differance take place , if you go over that trim and it will begin to porpose! under that trim and the motor slows a fraction and the bow spray from the hull comes out further forward .
Simply you need to get in tune with your boat!! and learn how it wants to work !!! not how you want it to work !!