Finally got off on a saturday and took my boat out and tried

to catch a fish or 2. After all the reading and all on the board, I took my boat up to WOT and notice it was running 6 and over at times (bumping around) then went to 7-8 and then back. I didn't hear any difference in the motor when the rpms went up to the 7-8 mark but I did back down all the way under 6. I was wandering if anyone could tell me what the operating rpm's should be on the 90hp 2stroke. It has a Solas stainless prop on it and I think it is a 19 but I cant remember. I do remember Hugh telling me that he had guys to tell him that if he want more speed the should change the prop. Im not interested in any more speed, just want to make sure Im not over revving my engine if I do run it at WOT (which I don't do very often or long at a time)

I have a four stroke 90 Yamaha and it is supposed to run between 5500 and 6000 rpm at wot......this is figured with two people and gear in the boat etc. I am running a Solas stainless 19 on mine and its perfect. Now then if your rpms are bouncing around and jumping up to 7-8.....sounds like you might have a spun prop hub. To check this take a marker and mark a line or a mark on your prop hub and on your prop shaft.....mark it so the marks line up......Then run your boat on the water and check your marks after you load the boat....if they do not line up you have a spun prop hub and will need to get a new one. The bad hub will give you poor performance and the over revving could damage your motor. I am sure that Hugh had your motor propped right.....but with your rpm's fluctuating like they are....I really think you have a bad prop hub.

G is right, but my Tach has got a short in it or something because I noticed it bouncing too. Tapped it because I too didn't hear any difference in the motor. Sure enough the tach went back to reading right. When I turn it off, it stays at 1000. Mine is not digital. My 60 Etec also is to run 5500-6000 WOT, but I am running the factory prop which I believe is a 15 ( I will have to go look). Hope yours is a bad tach and not the hub.

Possible it could be something wrong with your tach......if it revved to 7 grand you should have noticed a change in sound

Quote:

---

Originally Posted by "G"

Possible it could be something wrong with your tach......if it revved to 7 grand you should have noticed a change in sound

---

Or a big hole in your cowling, where a piston went through, when it hit the 8,000 rpm mark!

MOST outboards regardless of make or model, are designed to be at 5000-6000 rpm at wot as a general rule.

Quote:

---

Originally Posted by Shine Runner

G is right, but my Tach has got a short in it or something because I noticed it bouncing too. Tapped it because I too didn't hear any difference in the motor. Sure enough the tach went back to reading right. When I turn it off, it stays at 1000. Mine is not digital. My 60 Etec also is to run 5500-6000 WOT, but I am running the factory prop which I believe is a 15 ( I will have to go look). Hope yours is a bad tach and not the hub.

---

Yea Shine, no change in motor rpms but tach moving around, my tach also stays at 1000 also when not running. sounds like could be possible tach, thanks

Quote:

---

Originally Posted by mississippi

MOST outboards regardless of make or model, are designed to be at 5000-6000 rpm at wot as a general rule.

---

Thanks,

Larry you might check connections on back of Tach. Loose ground or sensor wires sometimes will cause flcuation.

most scared I've even been in my boat--I was running it out at the end of the day and glanced at the tach and it was pegged at 7 grand. Now-My mind went to calculating--I was running 60, it's a 150hp, and the prop is 25P--hmmm--it doesn't sound funny--better let off the gas. After sitting for a bit and thinking--I went back to the ramp. long story short--the tach was goofed---I got back there and turned the dial back and forth 5 or 6 times to "burnish" the contacts--no more problems. I have also heard it your running and the tach goes to zero (but the engine is still running fine) shut it down immediately as your volt reg is probably dead and all the wiring on the engine could be burnt up and or engine on fire.

one word rectifier If it is bad or going bad it will make your tach do crazy things

Quote:

---

Originally Posted by KDAVID1

most scared I've even been in my boat--I was running it out at the end of the day and glanced at the tach and it was pegged at 7 grand. Now-My mind went to calculating--I was running 60, it's a 150hp, and the prop is 25P--hmmm--it doesn't sound funny--better let off the gas. After sitting for a bit and thinking--I went back to the ramp. long story short--the tach was goofed---I got back there and turned the dial back and forth 5 or 6 times to "burnish" the contacts--no more problems. I have also heard it your running and the tach goes to zero (but the engine is still running fine) shut it down immediately as your volt reg is probably dead and all the wiring on the engine could be burnt up and or engine on fire.

---

Thanks KDavid

Quote:

---

Originally Posted by clfarms1

one word rectifier If it is bad or going bad it will make your tach do crazy things

---

Thanks clfarms1