New Toy not enough rpms

baxter66

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Sep 18, 2005
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20 Walk around<br />150 evinrude tuned up<br />34 mph at 4500 rpms wot gps evinrude tach<br />15x17 aluminum prop<br />I can trim motor till the prop breaks loose.<br />What do guys think i need pitch wise to get me in the correct range.
 

paulie0735

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Dec 6, 2005
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Re: New Toy not enough rpms

What make / model prop is it, must say the size sounds about right but you are 1000 rpm to low.... seems a bit od. The answer may be to just go down to a 15 but that seems a little small for a 150 on a 20' boat
 

baxter66

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Re: New Toy not enough rpms

I think it is an evinrude aluminum prop because it has very thick blade not like the michigan wheel I<br />have on my other boat.<br />This was with two people and about 80 gallons of fuel.
 

baxter66

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Re: New Toy not enough rpms

I take that back it is a michigan wheel looks like maybe 011007 15x17
 

paulie0735

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Re: New Toy not enough rpms

hummmmmm, How old is the engine? Are you sure it’s a 150, don't just believe the stickers on the cowl, check the serial number and cross check. When you say tuned up, are you saying 'modified'?
 

paulie0735

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Re: New Toy not enough rpms

Sorry Kenny, you beat me in with the engine question. No disrespect intended.
 

baxter66

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Re: New Toy not enough rpms

1997 e150exeuc<br />Not hopped up just had engine gone over my mechanic<br />new plugs comp. check 95 to 105 new water pump thermostats,lower unit service,power pack,carbs cleaned and decarbed motor.<br />Runs like champ planes the boat in seconds.<br />Where should the trim be to check height cav plate to hull? It looks like it is even with bottom of hull.Motor is mounted up 1 hole right now.
 

walleyehed

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Re: New Toy not enough rpms

Sorry Kenny, you beat me in with the engine question. No disrespect intended.
Don't feel bad about that....Excellent advice to check numbers, Good Job! :) <br /> The reason I asked about yr Model was now we know it's a 60* looper and we need to be looking for 5900-6000RPM with a normal load.<br />If we know the engine is healthy, we now know we are 700-800 off..<br />Best bet would be to raise the engine ONE hole at a time, then test...find the best heigth for that prop, then we can look into a better prop, but one thing I'd question before I bought a prop or moved anything, would be checking the tach for accuracy.
 

baxter66

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Re: New Toy not enough rpms

I have played with the setup alittle bit more. I put new tach in and changed prop to a new omc 15.5X15 aluminum prop. tach is now reading 5400 at wot at 36 mph gps. I raised the motor another hole got 35 mph at about 5200 and i can still trim motor all the way with out it venting. I dont understand why i lost rpm and speed when raising motor.Any thoughts?
 

walleyehed

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Re: New Toy not enough rpms

Losing speed could be slip, but RPM should have went up, not down.
Was the outside temp or humidity higher when you tested with it a hole higher?
Added weight to boat?
 

baxter66

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Re: New Toy not enough rpms

Weight was about the same.Temp was about 5 degrees hotter and the humidity was higher we had fog part of the day.I was supprised I could still trim the motor all the way up with out it venting. When its trimmed up it sounds like the exhaust is louder.
 

walleyehed

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Re: New Toy not enough rpms

If you can still trim all the way, we can go another hole up and test...are we in the second hole now? from the top...

EDIT; I see we're in the third hole up...I need to read closer...
"usually", the third hole is where we start to see some signs of venting....Not knowing what your water pressure is, I hate to say now, to go ahead and raise another hole..it'd be nice if we had a pressure gauge to know for sure...I'd hate to cause ya to burn it up....I think it would be fine, unless quite a bit of trim was used, but I don't want ya ruining something....
Do we have a reference of where the AV plate is in relation to boat bottom as it is now, trimmed level?
 

baxter66

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Re: New Toy not enough rpms

The AV plate is about 3/8" above the bottom. I do have a waterpressure guage that goes to 60 psi on my work bench that came with a bunch of guages I got of ebay.I just have not had time to figure out how it hooks up to this engine.
Thanks Kenny for your help.
 

walleyehed

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Re: New Toy not enough rpms

If the AV plate is only 3/8" above, go up to the next hole...we ain't going to lose any pressure that low.
 

baxter66

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Re: New Toy not enough rpms

Update Water pressure guage installed . I didn't get to raising outboard 1 more hole but I did spend the weekend removing my
bottom paint. My new figures are 5500 rpm 39.8 mph d:). Going to raise one more hole and test this weekend. Will post new numbers next week.
 

Ron G

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Re: New Toy not enough rpms

Thats getting better,is that still with the 15P?
 

baxter66

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Re: New Toy not enough rpms

Okay raised one more hole. It was the same as the last run but I could trim up till speed started to drop and rpm increased. The boat seems to run level. It seems to me when trimming up I should have a more bow up attiuded which would give me less boat in the water and help me take the swells better.
 

Crownie2

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Jul 26, 2006
Messages
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Re: New Toy not enough rpms

Sometimes if the motor is too high it will lose the ability to trim as high because it doesn't have as much water to bite into.

Don't know for sure if you are at that point yet.

Bob
 
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