Looking for a recommendation

[jrampey]

OK just bought a (new to me) boat and trying to make it better. The boat is a Tahoe Q6 with 4.3l mercruiser... It came with a 21P aluminum 3 blade prop. I have data on that prop and another - a 24P Mercury Turbo. Here's my info

1. Year, make and model of boat: 2007 Tahoe Q6

2. Length, width and base weight of boat: 20.5' X 8', 2800lbs


3. Number of people and gallons of gas normally on boat: 4 people, 35 gallons normally - but occasionally 7 to 9 people

4. What do you use the boat for: Watersports - skiing (slalom) and doubles


5. Is it a Deep Vee and if so how many degrees of deadrise: Yes a deep vee 22 degrees deadrise at transom

6. Year, make. manufacturer and model of motor: 2007 Mercruiser 4.3l carburetor


7. HP and gear ratio of motor IMPORTANT: 190 HP, 1.81 ratio

8. Manufacturer?s recommended Wide Open Throttle (WOT) range: 4400 - 4800 rpm


10. Is it a bass boat or does it have a pad bottom: No


11. Does it have a hydrafoil, dolefin or trim tabs: Just added 60# smarttabs from nauticus

12. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop

Prop #1: Generic Mercury Aluminum 21P 3 blade - 2 people, 25 gals gas, WOT - 5000, GPS - 44mph

Prop #2: Mercury Turbo SS 24P 3 blade ventilated - 2 people, 25 gals gas, WOT 4600, GPS 46mph

14. Are you at sea level or a higher elevation, give us the elevation in feet: 600 ft

15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM: Plugs look great, carb opens completely, compression good.

16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop: Aluminum was on boat since new. SS is extra that I've had from another boat.

17. Does the prop show any damage that you can see: Both are in great condition.

18. What problems are you trying to cure?: Aluminum prop is weak on holeshot and slow on top end. SS 24P - slow on holeshot (overrevs a little) but good topend. With heavy load in boat (7 people - really slow to plane overreving some)

I'm thinking... Stainless, loose the ventilation holes, step down 1" or 2" and, maybe 4 blades? All of the slip calculators indicate roughly 20% for these 2 props that I've tried. I had a bass boat with 150hp outboard... 4 blade stainless ventilated with 8% slip and a great holeshot. Can I get this one closer to that performance?

 

[Dhadley]

Re: Looking for a recommendation

Just a thought - a little more info on the ss prop will help. Mercury doesn't make the Turbo prop. Turbo does make a prop to fit on a Mercury. It'd help to know if you have a Mercury brand prop or a Turbo brand prop. The part number on the prop will tell what model it is and who made it.

 

[jrampey]

Re: Looking for a recommendation

Oops! I'm not sure how much I can give you... this prop was on another boat from way back. Had some minor dings - had it repaired by a local shop. I guess they ground out the number... unless its inside. I'll look tomorrow. Looks great now but only numbers are 75 76 does this help? It is cupped with a flared trailing edge hub. I remember it was a 24P from the number originally and the shop said they did nothing to change the pitch.

 

[jrampey]

Re: Looking for a recommendation

Oh... The blade had the yellow and gold "Turbo" label prior to repair. So It's definitely a Turbo.

 

[hwsiii]

Re: Looking for a recommendation

J, in my opinion a 21" Solas Amita 4 blade aluminum prop will bring your RPM down to the correct RPM range as well as make your hole shot muchhh better and increase your acceleration at all RPM through out the range. It will also reduce your prop slip, and it should be below 10%. With the 4th blade and the stern lift provided by these props they are an excellent value for the money, especially for water sports and heavy loads with the attendant prop slip from these appliations.
For a stainless steel prop Dhadley is the one to ask, as he has the requisite knowledge and experience in that field.


H

 

[jrampey]

Re: Looking for SS - DHadley?

Re: Looking for SS - DHadley?

Thanks... I'm going to look into the Solas 4 blade. I've always had Stainless before - always heard they don't flex, better acceleration, more speed and power for same pitch. Is this true? I guess I'm looking for recommendations for both - and opinions on their performance. DHadley - can you offer anymore advise with the little info that I gave?

 

[642mx]

Re: Looking for a recommendation

Aluminum is for beer cans, SS is for props.

I'd try a 23 pitch Mercury Revolution 4 or a Hill Marine 4 blade (23P). If your RPM's are a little low, have it labbed and they can add some RPM's back into it. Speed normally follows RPM's.... and its better to be over propped than under propped.

 

[hwsiii]

Re: Looking for a recommendation

J, here are some general guidelines.

I've always had Stainless before - always heard they don't flex, better acceleration, more speed and power for same pitch. Is this true? I guess I'm looking for recommendations for both - and opinions on their performance.

99% of the talk about aluminum flexing and causing them to not perform as well as SS props is misinformation. The overall reason that SS normally performs better than aluminum is the thinner blades, better blade geometry and design.

In my opinion the Solas prop I recommended will go as fast as the SS you are using now with muchhh better hole shot and acceleration throughout all RPM ranges and make the boat feel smoother and perform better, because it will reduce your prop slip a lot.

Prop Slip

H

 

[jrampey]

Re: Looking for a recommendation

J, here are some general guidelines.



99% of the talk about aluminum flexing and causing them to not perform as well as SS props is misinformation. The overall reason that SS normally performs better than aluminum is the thinner blades, better blade geometry and design.

In my opinion the Solas prop I recommended will go as fast as the SS you are using now with muchhh better hole shot and acceleration throughout all RPM ranges and make the boat feel smoother and perform better, because it will reduce your prop slip a lot.

Prop Slip

H

Hwsiii - you hit this nail on the head!

I just got this boat back in the water after the long hard winter. I bought the 21P Solas Aluminum blade that you recommended - and here are the numbers...

46.5 mph GPS @ 4600 rpm... great holeshot with 2 people and 50 lb dog, full fuel, 200 lbs of batteries.

Hwsii - you are the man!!! or woman???

 

[steelespike]

Re: Looking for a recommendation

hwsiii does an excellent job. Near as I can tell he has hit the nail on the head every time.

 

[hwsiii]

Re: Looking for a recommendation

J, I am very very happy to hear that the prop is working very well for you, and I was right in my recommendation.

And Spike I thank you very much for the very nice comment.

And by the way J, I am a man.



H