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OMC Prop question

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davespades

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I have a 68 Hydroswift with OM

I have a 68 Hydroswift with OMC outdrive that supports a pin drive prop. How high of pitch can I go on it without damage? Also can I use a stainless instead of the alum on it now or?
 
the pitch that makes your engi

the pitch that makes your engine run in the correct WOT rpm range is as high as you can go without lugging your engine and damaging it.
I don't recommend stainless on OMC electric shift drives. The mass of the heavy SS prop can stress or break clutch spring tangs during directional shifts. Propco makes aluminum props still for those drives. I think they're the only company still making them.
 
"Yes but how do I know where t

"Yes but how do I know where to stop at with the pitch? It seems when I open the boat up, it has about an inch or so of wasted throttle."
 
"don't stop with the throt

"don't stop with the throttle- take to full speed- as far as it goes- If you have the correct prop, your engine will be within the correct WOT rpm range.
WOT = wide open throttle i.e. full throttle.
most engines have a WOT recommended range of 4200-4600 rpm.
The prop is what controls his rpm, not the throttle. You verify correct pitch at full throttle.
All of this assumes of course that your engine is tuned up and making it's full rated horsepower. You can't check pitch unless the engine is running very well."
 
"If you are over-revving, &#40

"If you are over-revving, (maybe 5000 rpm) then you need to go up in pitch. If your engine is lugging (say 3800 rpm) then go down in pitch, or check for a lack of power from the engine."
 
"I honestlly was scared to tak

"I honestlly was scared to take it too high on RPS as I dont know when it will start to hurt the engine. It runs excellent however, it has a 17 pitch on it now as I was thinking of going to 18 or 20. Once its open, the extra inch or so of throttle does not seem to matter, just use more gas"
 
throwing higher pitch props on

throwing higher pitch props on it without paying attention to WOT rpm and correct pitch selection is a good way to destroy an engine. Sterndrive engines may overheat valvetrain components and tulip valves resulting in catastrophic engine failure if continually run in a lug condition.
 
"Thats why I said it seems to

"Thats why I said it seems to have some variance in the throttle. It seems that its still missing out on some throttle, I didnt think 1 or 2 pitch more would hurt it."
 
"you'll have more dead thr

"you'll have more dead throttle travel if you go up in pitch, not less."
 
"Ayuh,.....

And you Still h

"Ayuh,.....

And you Still haven't mentioned just What your RPMs are......"
 
"[img][/img] 'tis the seas

"
'tis the season of almost "passive aggressive" posting.... we're feeling too lazy to learn or look anything up this time of year.... just look for confirmation of our preconceived ideas...
If a person were to google "prop pitch" I'm sure the web would be their oyster. They would also learn that when installing an SS prop, one must decrease pitch due to the reduced flexing...
Some want to put a SS prop on their boat like it's mag wheels on a Mustang... hope we avoided some broken tangs at least - those OMC clutch springs are no longer available and are selling used on evilBay for $300+"
 
the season is over for that. I

the season is over for that. I dont know what you are referencing to when you say that HY. The point of the forum is just this.
 
"referencing this

POSTING

"referencing this

POSTING GUIDELINES

* DO a search of this board before posting any questions. Your question may have been already answered.
* DO include as much detail about your engine as possible including make, model, year, horsepower, model number, etc.
* DO include as much detail as possible about the situation with your engine including symptoms and evaluation done so far."
 
"[b]"I did all that. I wan

""I did all that. I wanted feedback. Dont go overboard about this...no pun intended."

Dave,..... I can't believe Hystat has already Wasted so much time with you,....
You've had all the theories of props explained to you,+ you've been asked Questions which you refuse to Answer........

Until You start Answering the Questions posed,....
I'd think you've seen all the answers you're going to get....."
 
"Why is everyone so aggressive

"Why is everyone so aggressive on here, I thought this was for helping others. Now your chiming in on me as well. I dont know what you mean by not answering questions, I am the one asking them. I did answer what I could. Why is this becoming a fedral case now? Back off and let those who arent so fluent in boating learn. The only question I havent answered was on RPMs only because I dont know as I have not had the boat out yet. Its around 4K."
 
"I monitor this board and make

"I monitor this board and make contributions when I can. I have seen this explained a number of times. The one thing you are not sure of is the most important, RPM. I do not know what my WOT is either on my 1974 OMC, but with the information supplied on this board and others, the number varies from 4200-4800 with some exceptions. RPM changes about 100-200 RPM per inch of pitch. Lower pitch will get you Higher RPM and Higher Pitch will get you Lower RPM. All this will mean nothing if you do not take an RPM reading at near Full Throttle. Once you have that, you will be able to decide which way to go. It would be good idea also to start another thread asking for help for someone with an OEM Manual for around 1968 OMC. I would believe the info you need about MFR recommended WOT will be there."
 
"[b]"The only question I h

""The only question I havent answered was on RPMs only because I dont know as I have not had the boat out yet. Its around 4K."

And without knowing Exactly what the RPMs at WOT are,....
This is going Nowhere......

Muchless,.... You Still haven't stated What the Motor is......"
 
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