new boat,, prop change

[black cherry tahoe]

have a 2011 tahoe q5i 19.5 ft open bow 4.3 alpha 1. not sure of specs on drive ratio or prop pitch i have. was thinking about stainless , or maybe just changing pitch. would like to see alittle more top end. speedo said 48 on a not great day with 4 people in it. need to get a good day this weekend to top it out and check rpm,s. will be cruising and towing some tubes occasionaly. boat is brand new. and broke it in . always looking for alittle more performance. any input would be great.

 

[BoatDrinksQ5]

Re: new boat,, prop change

My Q5sf has a prop with a model number on it. It can be looked up on Mercurypartsexpress.com most likely to determine the prop size/pitch. Most likely its a black max 14"x23p like mine - don't think much changed 2011-2012. Gear ratio 1.81 on mine - on stickers right where the trim arms connect to the outdrive (by trim anodes)
http://www.mercurypartsexpress.com/us/black-max-propeller-p441.html
Just got my 10hrs in and finally got WOT on mine!!!....was right in the sweet spot for a abnormally full boat (5.1people) around 4500-4600rpm and around 45-48 (busy/small lake so it was hard to get a good gps and rpm reading...)

I would assume if i got down to my normalish 2.1people it would be up near max rpm of 4800? But then again we have guests quite a bit...

 

[bnicov]

Re: new boat,, prop change

Try the same pitch in a stainless prop. You may get 2-4mph on the top end but will get all around better performance. BEWARE though, if you normally boat in waters with a lot of sunken timber/stumps or shoals, stick to an aluminum prop, the aluminum prop will give and break hopefully saving the lower unit, a stainless prop transfers the impact right up the drive and lots of damage happens with only a small contact.

 

[steelespike]

Re: new boat,, prop change

Welcome,get us the info in read this first"at the top of the prop forum.
Your prop pitch should be under the prop nut.With the prop pitch,your gear ratio, and couple of light load test runs we can tell better on your setup and what might be needed. wot rpm and speed by gps would be great.

 

[black cherry tahoe]

Re: new boat,, prop change

thx,, i will gps it tommorrow. if and when i go for the stainless prop, i see thier are lots to choose from. 200.00 to 500.00 dollars. whats the difference and what manufacturer is the one to go with. if i can spend 300 and get the same quality prop , i dont want to buy a name.

 

[steelespike]

Re: new boat,, prop change

The go fast guys may have some names to throw around You can be fairly certain that a $200 ss prop isn't going top deliver top of the line performance. Prop technology is a somewhat of a mystery with descriptions like aggressive,rake, cup, bow lift stern lift
more sophisticated technology. Terms like best speed,improved hole shot etc,etc.
The better setup you are with a good aluminum prop the less a ss will do for you.
Most ss props will deliver across the board improvement but it could vary from a few tenths to a few mph.
if you read up on the various brands/models. The guys will have some suggestions based on actual hands on experience
and their own setups.
There are al props like the Turning Point Hustler that provide close to ss performance at about 1/2 the price.

 

[theBrownskull]

Re: new boat,, prop change

I assume that the powerplant is a mercury/Mercruiser. I would wait until the break-in period is over so you can get the correct numbers without pushing the engine. You will need the wide open throttle (WOT) RPM's with the trim adjusted along with the speed, GPS if you have one. Then you can plug the variables in the formula either on the web site or manually. I prefer the manual formula.

You can also use the prop. selector program at the local dealer and try different props or find someone you know that will borrow you one. I had a 18' Starcraft boat w/ a 4.3 carb and it came with a 19 pitch aluminum prop. I went to the dealer and found a good prop. that way. The aluminum prop. allowed the engine to over-rev at 5200 RPM's. I first tried a 17pitch stainless, a Mirage, and found the WOT was 5100 a little to high. I then tried a 19 pitch Vengeance and it was right on the money at 4800 RPM's with great hole shot. I lost a 2 MPH over the aluminum on the top end.

Vengeance is Mercury's entry level prop. but seems to work good for me. I have a 2011 Tahoe 216, 5.0 MPI, right now and I am running a 17 pitch Vengeance. It works good. Better control that the 19 pitch aluminum it came with.

The Mercury website prop. selector is pretty good. It takes a trial and error sometimes to get it right.

 

[black cherry tahoe]

Re: new boat,, prop change

ok. its a 1.81 drive ratio. 23 degree pitch prop. boat weighs 2330 lbs. i want what everyone wants,, quick handles and top end. lol. today was beautiful but too ruff. could,nt get a good reading on r,s or top speed. the boats hull i,m sure will play a part in the optimum prop. but i would like to here from the knowledgeable guys out there. thx