Are my wot rpms too high ?

[StingRay_90V4]

So ive been enjoying my boats new found power and speed. From a dead stop when I floor it. It will pop out of the water and be on plane in about 2 seconds flat. As well as hit its top speed in no time flat. Or will do 44mph to 45mph. And that's verified by a gps. Although my boats speedometer says 46 mph. I wish.. Lol... My real question is. At my top speed my rpms are getting up there. My teach is accurate. It is on the correct setting of 6. For a 12 pole alternator. My rpms at top speed are about 5700 ish rpm at 45mph. And about 5600ish rpm at 44mph. I'm wondering if that high of an rpm is ok for the motor. I have read so much and so many different opinions on wot rpm. Some people say 5000rpm to 5500rpm. Some people say ring ot out to around 5800rpm. But its absolute max rpm is 6000rpm. I'm gettimf really close to that. What are your guys opinions as to of those rpm are to high or not ? I do have a 19p prop. But I loss a fair amoint of bottom end. My top speed basocally stays the same honestly. And where my enfone is raised on the transom a bit. My solias 17p works awesome. The one 19p seems to catch air it sounds like . Idk... It sounds like it... Any thoughys on that high of a rpm ? Also... My idle rpm is about 1200 rpm. Is that normal . Thanks in advance.

 

[ob]

Just because it will spin slightly over the recommended WOT operating range doesn't mean you have to exceed it and go balls out hair on fire every time you run it. I'd leave it where its at and let the engine breathe easy. You should lose at least 200 rpm with a 19 pitch compared to the same prop in a 17 providing the 19 hasn't been cut down in diameter from stock.

 

[ondarvr]

Might help to know what motor you're talking about.

 

[jbuote]

Hey StingRay_90V4 !

​I've been going through that on mine too.. Still new.. lol
I guess it depends on the engine too...
​For instance, Mine is a 71 50hp Johnson, and it has an acceptable WOT range of 5000-6000 rpm with peak HP at 5500 rpm... so running at 5800 I'd expect to be no problem...

​The 75 50hp, has (if I read right) WOT range of 4500-5500 with peak hp at 5000 rpm, so running at 5800 rpm would be over the acceptable rpms...

​If it were me, I'd want to find out what the acceptable rpm range is for your engine..
​Didn't see you state what engine you have, so I couldn't tell you.. LOL

​Hope that helps even if just a little.. You've helped me out before!

 

[ob]

Did a search on the OP's recent posts and it appears he has a 1992 Evinrude 90 hp.

 

[ondarvr]

Did a search on the OP's recent posts and it appears he has a 1992 Evinrude 90 hp.

​cross flow or looper

 

[jbuote]

Wow.. Just read a response OP made in one of my questions... In it, he states "I have a 1992 Evinrude 90 Hp crossflow"
​Looking it up now, but if someone knows offhand before I find it.,.. LOL

 

[ob]

Yea ,it would have to be a crossflow if it's a 92' model. The 90 &115 loopers didn't come to be until 95'.

 

[ondarvr]

Being a crossflow I'd let it rev, they tend to brake rings if lugged, well they all seem to break rings, but may live longer if not over propped.

 

[jbuote]

Well, it's a bit blurry but...
​This link to a brochure for '92 http://boatinfo.no/lib/evinrude/brochures/1992evinrude.html#/34

​Seems to indicate the RPM Range is 4500 - 5500, so if true, 5700-5800 is TOO HIGH...
​Should NOT exceed 5500, Should really have best performance at about 5000 if I understand all this right.. lol

 

[ondarvr]

Yes, that's the listed operating range, but they really tend to self destruct (from coking) if propped below the top end of the range, and going a little over isn't an issue.

 

[jbuote]

Ahh.. See? I learned something today too! (Regarding the crossflow... Not necessarily my engine.. lol)
​Thanks ondarvr !

 

[StingRay_90V4]

I dont know why i didnt think to add that in the info ?? Lol... It is indeed a 92 rude 90hp crossflow. Works amazing now that the timer base is finally freed up after sticking and barely moving at all sense the day we bought it 3 or 4 years ago. But we had no idea. We had nothing to compare it to to even know it wasn't working properly. I don't like to hold it at wot anymore at all for very long. I might go wot now once or twice a trip out now at best. And I only let it get to its max speed and rpm and only keep it there now for about 10 to 15 seconds tops now. I can't seem to get use to how much louder and higher it revs now. Compared to our 3cyl 88 60hp rude. It always sounded like it had no heart or soul to it. Lol... If you know what I mean. But now. After being fixed. At its top speed and rpm. It sounds like its going to take off. So I just wanna make sure its not over reving. It has never been rebuilt yet. Has low hours more then likely the mechanic said because the compression in it is so high. But all the paint on it inside is all original and never taken apart they said. And I don't wanna have to take it apart due to over reving it and damaging it. Yet our 19p omc prop is not that great at all. As I said in my first post. So this is the prop I have to use. Unless I get a 17p ss. But I have no idea what I will lose or gain by using a good 17p ss. On either rpms . top speed or hole shot.

 

[interalian]

I'm flirting with 6000rpm WOT on my '82 140, and thinking I need to swing a longer prop. Currently has a 17" aluminum on it and comes out of the hole like a popped cork.

I've heard that a 17" stainless acts more like a higher pitch prop. If that's true, I'd be inclined to keep with a 17 in stainless.

 

[StingRay_90V4]

I'm flirting with 6000rpm WOT on my '82 140, and thinking I need to swing a longer prop. Currently has a 17" aluminum on it and comes out of the hole like a popped cork.

I've heard that a 17" stainless acts more like a higher pitch prop. If that's true, I'd be inclined to keep with a 17 in stainless.

I bet the 90 converted to a 140 on the same boat the 90 was on must just fly . the hole shot and the top speed must be awesome. What size prop are you on right now. Like I was saying. My 90 with the standard 17p is flirting with 5700 ish rpm. Maybe even 5800 rpm at 45mph. But its really hard to tell when I'm trying to watch the lake. The boats bouncing up and down. Lol... 5700 for sure. Maybe 5750 or 5800... I just dont know if those rpms are to high ? And how long could or do people hold them that high ?

Also if a 17p stainless acts more like a 19p aluminum. Should I be looking for a 15 or 16p ss to keep my hole shot and top speed the same but have lower rpm ? It gets so confusing . lol

 

[interalian]

As noted in post #14, I'm running a 17" aluminum prop. According to others, the 90 should have a better hole shot than the 140 due to torque curve, but I don't remember it ever being as quick as it is now. You can see how it runs here, although I was still breaking it in and didn't hold WOT to full revs: https://www.youtube.com/watch?v=Kt4AFg92Cc0

 

[StingRay_90V4]

As noted in post #14, I'm running a 17" aluminum prop. According to others, the 90 should have a better hole shot than the 140 due to torque curve, but I don't remember it ever being as quick as it is now. You can see how it runs here, although I was still breaking it in and didn't hold WOT to full revs: https://www.youtube.com/watch?v=Kt4AFg92Cc0

Sorry... My bad.. I am bad at times for skimming over info . I watched the video. It seems to work really well. I don't think my 90 has any better hole shot then that. Looks like they are on par. Hard to judge ober a video though. Looks like you may want a 19p. And you may be looking at near 50mph. If not more.

I am gonna browse through your 90 to 140 post and see what all is involved and what different parts I would need to buy. Of I ever have to rebuilt it and hotbget a new boat first. I may just do that to my 90 as well. Was it worth it ?

After watching your video a second time. I feel like and it kinda looks like your boat does indeed have a slightly better hole shot. My 90 is amzing out of the hole. But yours looks like it has a rocket propelling it. Lol

 

[interalian]

Sorry... My bad.. I am bad at times for skimming over info . I watched the video. It seems to work really well. I don't think my 90 has any better hole shot then that. Looks like they are on par. Hard to judge ober a video though. Looks like you may want a 19p. And you may be looking at near 50mph. If not more.

I am gonna browse through your 90 to 140 post and see what all is involved and what different parts I would need to buy. Of I ever have to rebuilt it and hotbget a new boat first. I may just do that to my 90 as well. Was it worth it ?

After watching your video a second time. I feel like and it kinda looks like your boat does indeed have a slightly better hole shot. My 90 is amzing out of the hole. But yours looks like it has a rocket propelling it. Lol

Better browse quick - the avaricious morons running Photobucket have decreed that I'm on their list of 3rd party link abusers and want $400US to allow continuation of my linked photos. They can go whistle - there's no way I'll fork out that much dough for the privilege of using their bloatware-ridden site.

Now, was it worth it? Probably not from a purely financial perspective. I could have lived with the 90 as it was for as much use as we get out of the boat. Of course, the gearhead in me eschews financial prudence and shouts "hammer down!!".

 

[V153]

Ha! You call that a hole-shot? ...

Bone stock '83 140. 13 3/4 x 23 SRX. 62.9 mph.

Problem turned out to be a split in the hose from thermostat cover to heads. Didn't leak at idle but at higher revs it peed up all over under the motor cover.

www.youtube.com/watch?v=Lqat6iRbpRo

Please ignore my obnoxious buddy JR ...

 

[V153]

Crossflows are just gettin warmed up @ 5700. I routinely run em in excess of 6K. Not all day mind you. Just when I have to put somebody that thinks they have a fast boat in their place.