new prop no workie

[bandit86]

87 25ft bayliner, omc 5.7, the prop on my boat was 15x17. it did 43mph easy at 4300rpm. after finding a ding in the prop, i got a new one, same size, tops out at 35mph, about 3800rpm full throttle. whats the deal? I know props can make a big difference, but it's the same size andi lost 8mph on gps

 

[walleyehed]

Re: new prop no workie

What manufacture was the early 17? I'd guess it to be an OMC by the numbers you give, just because it's proven to be a better design than most, but if you would, tell us what manufacture and model both props are.

 

[bandit86]

Re: new prop no workie

I am not sure what the old prop is, it came with the boat. the new one is a Quicksilver

 

[walleyehed]

Re: new prop no workie

Well, for one thing, I bet we have changed blade designs.
I'm "thinking" maybe we have a prop (the first one) that has either been worked, or is a std 391200 15X17 OMC..I've yet to find any aluminum that will out-perform that prop for some reason.......
We're talking alot of speed and RPM difference, so are you sure the new prop is a 17P?
You didn't go to a 4-blade 17P did you?

 

[bandit86]

Re: new prop no workie

no, it's a 3 blade as well. I'm going to take both props tomorrow back to the place I got it from

 

[bandit86]

Re: new prop no workie

so here is the info, everything I could dig up

old: no manufacturese name, in the back there is a stamped J, 15x17, D2, 391200.
it has a rubber insulated hub, the blades start about half inches back from the leading edge of the hub.

new: Quicksilver, K15x17P, there is a 3012 stamed on the side, blades start right at the leading edge of the prop

 

[walleyehed]

Re: new prop no workie

As I said...it appeared to be an OMC 391200 by what you said, and again, in aluminum, I haven't found anything better.
That prop is a QA3012XT Black Diamond...it is designed as a replacement for the 391200, but something else is wrong to get the massive change you did, and I must say "I'm stumped"....
I'd take them both to a prop shop and ask what the deal is....

 

[bandit86]

Re: new prop no workie

I put the old prop back on to try it, and I hit old speeds at the old rpm

 

[turbodriven]

Re: new prop no workie

I would say it's very possible that the props have different designs and function differently.

My original 14x19 prop that came with the boat (OEM mercury prop?) used to easily hit 44+ mph. After hitting a rock and damaging it I replaced it with a Hustler 14x19 prop I found on sale and now I can't get past 35mph. It actually performs closer to my mercury 14x17 prop that I use as a spare. *shrug.

 

[bandit86]

Re: new prop no workie

what about props that lift the bow or stern, would that be a difference in design factor

 

[mrtool2u]

Re: new prop no workie

Why not just get the old prop fixed and return the new prop,,assumeing it is in new condition. My brother has a older 17 foot Glasstron with a 1995 115 Rude with a 14x19 pitch OMC prop,,steady 45 mph at 5200 rpms,,when that prop lost a blade we bought a michigan wheel prop same dimensions and it ran like a turd,,so we bought the exact same OMC prop and presto,the boat was back...Did you ever consider a Raker,,I put a older style Raker on my boat and it really did a nice job for my 120 Johnny. Walleyehed is right,,the OMC prop did seem like a much better prop in the aluminum line.

 

[walleyehed]

Re: new prop no workie

Why not just get the old prop fixed and return the new prop,,assumeing it is in new condition. My brother has a older 17 foot Glasstron with a 1995 115 Rude with a 14x19 pitch OMC prop,,steady 45 mph at 5200 rpms,,when that prop lost a blade we bought a michigan wheel prop same dimensions and it ran like a turd,,so we bought the exact same OMC prop and presto,the boat was back...Did you ever consider a Raker,,I put a older style Raker on my boat and it really did a nice job for my 120 Johnny. Walleyehed is right,,the OMC prop did seem like a much better prop in the aluminum line.

We have to be careful with some of these figures...5200, 19P, and 45mph equates to 5% slip...highly unlikely...probably a speedo or tach error...
Anyway, I still think something is wrong with your new prop and it needs to be checked before you get stuck with it.....

Bandit, Yes, stern vs. bow vs. over-all lifter are all different blade designs, and on the wrong application, will perform POOR at best.

 

[bandit86]

Re: new prop no workie

I found an omc prop in the paper with my numbers, gonna try to get it this aft.
as for the new quicksilver, the paint chipped, I picked up a fishingline last trip in (see other boat topics post -in trouble with the fishermen) that somehow made it to the other side of the channel

 

[skibug]

Re: new prop no workie

I would bet that the new prop that you tried had more cup to the blades, which caused the drop in rpm and speed.

 

[bandit86]

Re: new prop no workie

yes it does, the place I got it from insisted on it baing the same size and working. LESSON LEARNED.

P.S. Dont buy props from Hully Gully in London Ontario

 

[walleyehed]

Re: new prop no workie

I would bet that the new prop that you tried had more cup to the blades, which caused the drop in rpm and speed.

Not 500RPM and 8mph.....
The 391200 has MORE cup...that's why it's as efficient as it is...The quicksilver prop has a problem....and it ain't too much cup...atleast it would be the first one in history if it did.

 

[mrtool2u]

Re: new prop no workie

Walleyehed,,,quite possibly the speedo is off,,,besides,,he is only getting 42 mph this year,,possibly it was 42 last year also. Reguardless,that OMC prop was the way to go.

 

[walleyehed]

Re: new prop no workie

Agree......