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Author Topic:   Repairing a SS prop - Effects on 18/19 Outrage performance
ewalsh posted 05-15-2003 08:45 PM ET (US)   Profile for ewalsh   Send Email to ewalsh  
I recently posted that the 14.5x19 SS prop on my Johnson 150hp classic Outrage 19 was spinning the untrimmed motor to about 5,800 rpm and 43 MPH (I was expecting 50mph @ 5,500rpm based on the previous owner's representations). The boat was also porpoising at that speed with 600lbs of men around the center console, a good load of gas, and 100lbs of kids up front.

Most folks that I have spoken with said that it is impossible for a 150hp to spin a 14.5x19 on a 19 Outrage to those RPMs with such a low speed. They say I must have a different prop. Well maybe they are both right.

My prop IS clearly stamped "14.5x19", but my repair records from the previous owner also indicate that the prop has seen 1 (maybe 2) prop repairs (nicks, scuffs, etc). Recently I learned that SS props are typically repaired by having the blade edges ground down a bit to remove the dings, etc. True? If so, this method of repair must decrease the prop's diameter, no? And if so, that means my prop may be 15.5x? (18, 17?)

Is this a plausible theory? How would I measure the diameter of the existing prop to make sure it is still 19"?

Thank you, Ed

whalersman posted 05-15-2003 09:16 PM ET (US)     Profile for whalersman  Send Email to whalersman     

I am going through some of the same things on my 1985 Outrage 18 with a 150 HP Evinrude with 375 hours on it...

I now have 3 props....
1. 15 1/2 diameter x 15 pitch Aluminum
2. 15 diamter x 17 pitch Auminum (NEW)
3. 14 1/2 diamter x 19 pitch SS

I just purchased #2 prop to try it out. I am getting 5,000 RPM's and about 40 MPH on the fish finder. I do not have a GPS yet..

I purchased this new prop because #1 had quite a few nicks and #3 was a Stainless Steel and I have to be too carefull with a prop like that because of the waters I travel in...

I am satisfied with the #2 prop for right now... My next step is to raise the engine up one hole from the bottom position. The original owner lowered the engine to the bottom most hole thinking it would serve his water skiing needs better. I can see that the cavitation plate is too low and creating two Rooster Tails....

I don't think there is anyway that you or I could measure the Diameter or the Pitch of a prop without proper equipment. Leave that up to the prop shop..

I would recommend buying a new prop if a prop shop let you try several props of different "pitch" before you buy...

The WOT RPM's on most of the older OMC 150's are from 4500 to 5500 RPM and the book says that at 5000 RPM the engine is delivering the max of 150 HP...

It sounds as though you also are loading your boat down too much for testing. I think testing should be done with no more then 2 people on board and little to no gear...

Dick posted 05-15-2003 10:13 PM ET (US)     Profile for Dick  Send Email to Dick     
I don't have a performance sheet on the 19OR but the test sheet for the 20 OR shows the following.
150 Johnson EXE
0-30 MPH 6.75
Sec to plane 4.68
43 MPH @ 5500 rpm
prop 15X17 SST
2 people/345#s
Engine rec at 1 hole up no idea what how the test motor was mounted.


Sal DiMercurio posted 05-15-2003 10:45 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Ok, first things first.
# 1, if your prop has been ground down, the diameter would be smaller, from 14.50 to 14.25, not get bigger to a 15.50, it wont bother the pitch unless you straighten the prop.
By grinding down the outer edges of all 3 blades, in order to remove any diameter at all like 3/4 of an inch, they would only take 1/4 of an inch off each blade.
# 2 in order to measure the correct diameter of a prop, measure from dead center of the hole in the center of the prop, to one outside edge of the blade, then double that & it gives you the diameter.
# 3, I really must question if your tach is correct, as I doubht a 150 can twist a 14.50 x 19 to 5,800 rpms trimmed all the way in with a load like you had on the boat.
# 4, you can't measure the pitch withour a form thats cast to a 19 pitch, it must be checked by a reliable prop shop.
# 5, yes your engine is far to low on the transom, this is the main cause for porpoising, bring it up at "LEAST" 2 holes.
# 6, you test a prop by loading the boat with a normal load that you will be using most of the time.
You bring her to wot, then trim her out as much as possible till she breaks loose, then bring her back in till she holds, then mark your rpms.
# 7 If she's turning 5,800 rpms tucked all the way in, she will rev to 6,200 trimmed out.
My suggestion is, bring the prop to a prop shop & have them check for dia & pitch, then have your tach checked because it's really not in the books to turn thst many rpms under those conditions with a 150, pretty tough even for a 200 HP.
ewalsh posted 05-15-2003 11:01 PM ET (US)     Profile for ewalsh  Send Email to ewalsh     
Thanks to all for their repies.

Sal, you bring up some great thoughts. TO address each of your points:

#1 - Sorry about that, I meant to type 14.5x(18, 17) not 15.5x

#2 - THANK YOU - exactly what I wanted to know. I'll measure tom. and report back

#3 - THe tach was tested against a known good one. The engine wasn't trimmed all the way in, the trim gauge was in teh middle.

#4 - check

#5 - I've never understood the whole "hole" thing. My engine has not mounting holes... There are slots in the lower bolt holes and fixed holes in the upper. FWIW, the engine sits about an inch off the top of the transom... Is it still low? This is an original boat/motor set up by a whaler dealer - could they have screwed up the motor install?

#6 - Check

#7 - I'm planning to do some testing this weekend- - I really do think that the prop has lost a lot of its diameter, so hopefully, a new 14.5x19 will bring me back online.

Thanks again, Ed

jimh posted 05-15-2003 11:42 PM ET (US)     Profile for jimh  Send Email to jimh     
I would also check the propeller to see if the hub has been spun.
Sal DiMercurio posted 05-16-2003 01:17 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
To be honest, i'v "NEVER" seen an engine mounted correctly by a dealer, most just plop them on the transom & the owner dosen't know the difference between a fine tuned setup & just rigging it as fast as they can.
Yes your engine height is totally adjustable, the bottom bolts are in a slot that moves vertical, the top bolt are in holes, should be 4 of them vertical.
To raise your engine, remove the top bolts & just loosen the bottom [ slot ] bolts, put a floor jack under the skeg of the engine, with a 2x4 or 4x4 on top of it, your going to need a couple buddies to steady the engine as you jack it up 2 holes, put the top bolts back in [ put plenty of sealant on the bolts ] & tighten, then do the same to the bottom bolts, being sure you really piled the sealer on those bolts, then tighten them up.
Your done.
If by any chance she blows out or ventilates, bring her back down a hole.
Have that prop checked to be certain it's true, then I would order a s/s Stiletto of the same size, it will change the whole ride of the boat by lifting the whole boat & making it ride higher on the water, could also give a few mph more at top end.
I don't feel the hub is spun or it would totally break loose like you lost the prop, but would allow you to idle in some cases.
It's baffeling why that 150 is able to twist that much pitch because it shouldn't be able to, mounted that low & with the load you had on the boat.
Raising the engine should cure the porpoising as that engine isn't that heavy.
Question, does she still porpoise at wot ?
It should stablize at wot but leap like a frog between 4,000 & 5,000 rpms if she'sto low on the transom.
Sal DiMercurio posted 05-16-2003 01:23 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Stiletto size is s/s [ very highly polished ]14.25 x 19.....$249 total delivered to your door from Aftermarket.
I honestly feel omc props other then the high performance props, aren't worth a darn.
Their thick & clumsy compared to Merc or Stilettos.
ewalsh posted 05-16-2003 08:23 AM ET (US)     Profile for ewalsh  Send Email to ewalsh     

Thanks again for sharing your knowledge!

I will check out the engine mounting position this weekend and report back. Yes, she does porpoise at WOT.

I too can't figure out why the motor spins the 14.5x19 prop with a good load to 5,800 RPM... I can only imaging the prop is out of spec. Also, I have been told that the 1991 Johnson "SilverStar" engine is hot, possibly running 175hp carbs.

In the meanwhile, I'll begin my search for a Stilleto prop.

Regards, Ed

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