RIGHT PROP

[Vantoo]

Hello, I have a question for some of you guys that know props and setups. This is probably a loaded question because I have not trie the boat yet. Weather not fit here in East Tennesse this weekend. I have a 1985 Ebbtide Dyna-Trak 156 16 ft boat with a 1979 70 hp evinrude outboard. I was just wondering if you guys would have any idea if the 13 3/4 x 15 alum prop that is currently on the motor would be the correct one or close. Thanks for the replys. Rick

 

[adc]

Re: RIGHT PROP

For your motor, the standard prop is a 13-1/4 x 17.<br /><br />Have you looked here...?<br /><br /> http://epc.brp.com/default.aspx?brands=ej&lang=E parts for OMC

 

[Silvertip]

Re: RIGHT PROP

You will know more when you do the on-water test. Run it wide open throttle, best trim setting, average load and carefully note engine RPM at wide open throttle and maximum speed at that rpm (best measured with GPS since normal boat speedos are notoriously inaccurate). If the WOT rpm is higher than the engines maximum rated rpm, the prop has too little pitch. If its under the max rpm range it has too much pitch. If its right at or slightly over the max rpm, its the correct prop. All of this assumes the engine is good state of tune and running properly.

 

[Vantoo]

Re: RIGHT PROP

ok guys, here we go. I tried the boat yesterday and WOT was 5900, and it is supposed to be 4500 to 5500 according to the plate on the motor. I have a 13 3/4 x 15 prop on it now. Do I need to change props or be just as well off watching my tach and running about 5400? thanks for any help.

 

[Dunaruna]

Re: RIGHT PROP

There is always the danger of over revving the motor.<br /><br />Change to the 17", it'll put you in the correct WOT range.<br /><br />Aldo

 

[Vantoo]

Re: RIGHT PROP

Originally posted by Dunaruna:<br /> There is always the danger of over revving the motor.<br /><br />Change to the 17", it'll put you in the correct WOT range.<br /><br />Aldo

how about a 14 x 17 prop....

 

[Dhadley]

Re: RIGHT PROP

For long engine life with todays fuel, 5900 is really good. Theres no reason to be afraid of 5900 -- or even more.

 

[Vantoo]

Re: RIGHT PROP

Originally posted by Dhadley:<br /> For long engine life with todays fuel, 5900 is really good. Theres no reason to be afraid of 5900 -- or even more.

Don't get me wrong, I appreciate your reply. But, the tag on my engine says 5500 max.... you think there is no danger running 5900?

 

[walleyehed]

Re: RIGHT PROP

Your engine was designed to run of fuel that was produced in 1979...the fuel we have today is half the quality it was back then.<br />As Dhadley said, it's best (Been proven) that 5800-6000RPM is the "best" range for that engine on "todays" fuel. It will run better and smoother at 5900 than it will at 5500 anyway.

 

[Dunaruna]

Re: RIGHT PROP

Originally posted by walleyehed:<br /> ...the fuel we have today is half the quality it was back then.<br />

Is that a typo or are you suggesting that a lesser quality fuel improves longevity?

 

[walleyehed]

Re: RIGHT PROP

No, I'm saying a "Lesser quality fuel" has different combustion charactoristics, and an engine that has ports, ignition, comp ratio, timing and cooling systems that were set-up (read designed) for that vintage of fuel, takes some changes to make it run anywhere near the same on todays fuel.<br />There is nothing "Good" about our fuel today...the properties suck compared to how it was in the late 70's....<br />My 200 is book-rated for 4750-5750...if I get a prop mounted that allows less than about 5300RPM, my cylinder head temp climbs pretty good. I've run this engine around 6500RPM with no problems. I set it up for 5800-5900 for everyday running. I put 487 hours on it this summer and all 6 pistons have just a slight "port shadow" on the intake side from being just slightly rich, and the rest of the piston top is dark with maybe a very fine carbon deposite. I cruise very little as I have a habit of finding max travel of the throttle, I burn alot of fuel, but cover some serious territory.<br />This engine has been flawless since the rebuild...I can't say that for the people running 5000-5400 with these engines....most of these are in trouble after 200-300hrs.

 

[Dunaruna]

Re: RIGHT PROP

Thanks for the explaination.<br /><br />Would it also be fair to say that TCW3 plays a part in high rev longevity? (compared to whatever was available in '79).

 

[Vantoo]

Re: RIGHT PROP

Originally posted by walleyehed:<br /> No, I'm saying a "Lesser quality fuel" has different combustion charactoristics, and an engine that has ports, ignition, comp ratio, timing and cooling systems that were set-up (read designed) for that vintage of fuel, takes some changes to make it run anywhere near the same on todays fuel.<br />There is nothing "Good" about our fuel today...the properties suck compared to how it was in the late 70's....<br />My 200 is book-rated for 4750-5750...if I get a prop mounted that allows less than about 5300RPM, my cylinder head temp climbs pretty good. I've run this engine around 6500RPM with no problems. I set it up for 5800-5900 for everyday running. I put 487 hours on it this summer and all 6 pistons have just a slight "port shadow" on the intake side from being just slightly rich, and the rest of the piston top is dark with maybe a very fine carbon deposite. I cruise very little as I have a habit of finding max travel of the throttle, I burn alot of fuel, but cover some serious territory.<br />This engine has been flawless since the rebuild...I can't say that for the people running 5000-5400 with these engines....most of these are in trouble after 200-300hrs.

So you think running my engine at 5900 RPM, it would run cooler than the recommended 5500 RPM?

 

[Dhadley]

Re: RIGHT PROP

Cooler combustion temps, yes.<br /><br />A related "recommended RPM" sidenote -- for 2006 Yamaha is up-ing their recommended RPM to 6000 on their 2 strokes. It'll have a huge impact on tests where the motors are only allowed to go to the printed top rpm.

 

[imported_bjs]

Re: RIGHT PROP

im not trying to be rude. but i dont think all you boaters are Turing as many rpm's as your tach says Ive put to many car motors on dynos and took tachs that people have in there race cars and there not even close to what the dyno tach are.can be 300 rpms off those rods in those boat motors will not take that kind of rpms.the gas is not desinged for that kind of rpm's.thats not high octane gas.if you take a small block chevy with an aftermarket crank and rods it will last twice as long as a stock crank and rods.because the stock stuff will crack and break form that kind of abuse.but the aftermarket stuff will last for 2to3 race seasons and those pistons in those boat motors are cast not even alm.they wont take the heat that alum will and the more rpm the more heat your making wich leads to melt down with pump gas rated at 89 octane.and thats not even at the motor octane.thats at the pump octane.who knows what the octane is at the motor.so i would stay in the rpm range it says on the sticker.

 

[walleyehed]

Re: RIGHT PROP

Brad, with all due respect, don't even try to compare an auto 4-stroke to a Marine 2-stroke.<br />#1., I have used every type of tach in production on my 200, including a direct-drive intended for irrigation engines...I know EXACTLY what my engine turns. And, when playing with exhaust gas temps and cylinder head temps, ya learn real quick what the truth is.<br />#2., Dhadley has to give back all of the countless Trophies, plauqes and awards he's received over many, many years of Boat racing, and Marine engine and parts developement, because apparently, he never tested anything to prove this, so he really couldn't have won all of these items because he didn't stick to the factory specs, and still doesn't, because we've researched and tested, then tested, and then tested some, and then tested more and found out maybe this way works a bit better.<br />#3., If you choose to run ANY outboard at a max RPM of LESS than the TOP of the range, I can tell you right now, my engine will outlast yours and have twice the life.<br />The older the engine is, the more important it is to keep the RPM set-up to achieve at and better yet,slightly above Max recommended.<br />The info posted by Dhadley and myself on this issue is not a "Thought", it is a proven "Fact".<br />By the way, Brad, Dhadley has some V4's he turns close to 9000RPM, and the funny thing is they stay together....while blowing past V6's in the process....NO, don't go set up for 9K...a stock engine(2-stroke carbed) runs out of air before it can over-rev anyway.

 

[imported_bjs]

Re: RIGHT PROP

ok so i wont compare butit still has piston and rods and a carb and a crank.so iguess i dont know what im talking about thanks for the input.

 

[walleyehed]

Re: RIGHT PROP

Brad, does a 4-stroke have transfer ports in the side of the cylinder??? Does a 4-stroke have reeds???<br />The rods have nothing to do with running a bit faster with the same "load" on the engine.<br />Pistons and rings...yes, but then that would open the door for me to include Aircraft piston engines and how we AVOID high manifold pressure and LOW RPM (Read lugging the engine). I've had a ton of those apart, and I can tell which have been run in the areas that should be avoided. We're talking a few hundred RPM more, not 2-3000.<br /><br />By Dunaruna;<br />

Would it also be fair to say that TCW3 plays a part in high rev longevity? (compared to whatever was available in '79).<br />

Yes, I think some credit should be given in that area as well...It seems we see alot less piston scuffing from lack of lube...at least that's what I've seen since about 1980-up on older engines.<br />As for new TC-W3 helping prevent major problems due to RPM being higher, I don't feel that is as much an issue because these older rigs are premix, and 50:1 is actually rich on oil even at WOT, just slightly...I do think some of the additives are better suited to keeping an engine cleaner in the newer TC-W3 oils, but PM plays a big part too.

 

[imported_bjs]

Re: RIGHT PROP

im sorry i said anything.i wont stir up the more than i already did.happy boating.a motor is just an air pump weather its a 4 stroke or two stroke.i will find another board to voice my opinions.

 

[walleyehed]

Re: RIGHT PROP

Nothing wrong with opinion Brad....<br />

but i dont think all you boaters are Turing as many rpm's as your tach says Ive put to many car motors on dynos and took tachs that people have in there race cars and there not even close to what the dyno tach are.can be 300 rpms off those rods in those boat motors will not take that kind of rpms.the gas is not desinged for that kind of rpm's.

I don't see this as opinion...<br />The rods in the outboards will take more RPM than what the reeds will allow the engine to turn..<br />If you want the correct info, atleast pay attention to Dhadley..he won't lead you astray, and even if you don't think I know what I'm talking about, I have the Data to prove what I say.<br />Post away