Beating a dead horse with a prop wrench **UPDATE**

[NathanY]

Boat: 1991 Smokercraft Magnum 16'2"<br />Motor: 1990 60hp Evinrude <br />Prop: OMC Aluminum 13 3/4 X 15<br />RPM's: 5850@WOT<br />Speed: 29MPH@5900RPM<br /><br />I want to change to a stainless steel prop. Boat is not real heavy, nor is it loaded heavy. I dont need to go any faster but would like better hole shot and just better performance. What do I need?

 

[Solittle]

Re: Beating a dead horse with a prop wrench **UPDATE**

Your only option to get a better hole shot may be to get a bigger motor. You are already proped just where you ought to be. If you went to a prop with less pitch your would increase your rpm (& hole shot) plus probably decrease your max speed - and you are already at the upper end. My guess it that your max rated rpm is 5500 and you are already turning 5850-5900.<br /><br />Going to SS with the same 13 3/4 X 15 might help some.

 

[ledgefinder]

Re: Beating a dead horse with a prop wrench **UPDATE**

Did you already lift the motor on the transom?

 

[CalicoKid]

Re: Beating a dead horse with a prop wrench **UPDATE**

You could probably see a lot of handling and acceleration improvements with a stainless prop... as long as you're perceptive to subtleties. All of the high-tech development is in stainless. Research the best design for your boat and snatch one up on ebay for half price. A prop can be drilled with exhaust relief holes that allow more prop-slip at takeoff resulting in higher rpms and horsepower for holeshot. As long as the holes aren't too big, top end should not be affected.<br /><br />You may also see improvements by attaching tabs to your hull or a foil to your anti-cav. plate. <br /><br />I'd start with the prop...

 

[Silvertip]

Re: Beating a dead horse with a prop wrench **UPDATE**

Hole shot and top speed are a compromise. You can't have both but you can compromise. How are you determining speed? (GPS or locator with speed transducer??). I'm familiar with your boat and there is definitely something wrong (not with the engine or the boat, but probably the speed reading). I have a 40 HP Evinrude on an Alumacraft Navigator 165CS and can run a tick faster than that (GPS and locator)with two people, full of fuel and fish in the live well. My fishing buddy runs a 50 Merc on a very similar Lund and is about about 2 MPH faster than me. Your combination should be in the 34 - 35 MPH bracket and hole shot should not be a problem unless the boat is heavily loaded -- especially in the rear. If you have a standard OMC prop it should be cupped but you might want to check it to make sure. Otherwise try moving heavy stuff to the front of the boat to improve hole shot. Your RPM is right on and less pitch would probably put you further over the recommended limit. That's not a problem if you really want hole shot and will keep an eye on the tach so you don't over-rev.

 

[G DANE]

Re: Beating a dead horse with a prop wrench **UPDATE**

Your gear ratio is 12/29. <br />You should be going 32 MPH with 10% slip at 5850 RPM with a 15". I would stick to 15" stainless ans try to lift motor to gain speed. Wait a bit with the hub drilling.

 

[NathanY]

Re: Beating a dead horse with a prop wrench **UPDATE**

29 is what my speedo says. But, my friends boat says about the same when running next to me. I know that water powered speedos are in accurate, but it is all I have. <br /><br />Also max RPM is 6000 @WOT for this engine.

 

[Silvertip]

Re: Beating a dead horse with a prop wrench **UPDATE**

Before you start throwing money at props or prop modifications, check with your buddies and see if they have a GPS. Borrow it (and its owner) for a few hours and get some accurate speed readings. My current boat and every previous one gave either overly optimistic or terribly low readings. In the end though, the tach will provide the best indicator as to what optimum performance is. If 6000 rpm is your target, drop back on pitch or raise the engine one notch if it hasn't already been raised. By the way, all performance tests are meaningless if you are attempting to increase performance with an engine that is not properly tuned or is simply getting tired.

 

[phatmanmike]

Re: Beating a dead horse with a prop wrench **UPDATE**

3 words:<br /><br />drill relief holes

 

[walleyehed]

Re: Beating a dead horse with a prop wrench **UPDATE**

I'm going to give the relief holes a 2-thumbs up my self as well, but it would be good info to know how high your X-dimension is....and please, talk to me before you drill holes...I'll send you an email so you have my winter address.<br />BTW, 10% slip on an alum boat is extremely efficient, maybe even TOO efficient. I'd guess 12-15% would be closer...

 

[NathanY]

Re: Beating a dead horse with a prop wrench **UPDATE**

Ok here is the deal, I GPS'd the speed (wife got me one for Christmas) and the best the boat will do is 30.4 mph (ground speed)@5900 RPM. Will a cupped SS prop help me out?

 

[walleyehed]

Re: Beating a dead horse with a prop wrench **UPDATE**

Yes, it will. There are more set-up options with an SS prop, and it will produce higher efficiency from day-one.