Tahoe 195 150hp optimax prop question

[acuaholic]

Hello, I just purchased a tahoe 195 deck boat with a 150 hp opti, currently it has a SS 21p 3 blade prop, first time out with family of 2 adults and 4 kids about 600lb total and full tank of gas 46gal the boat got 48mph at 5,600 rpm. Speed is not and issue but I like to wakeboard a bit and kids got a 4 person tube. I was told a high five prop would do the trick, I was looking at the mercury prop selection and if I put in the boats specs with rpms and speed and what prop is running now, it tells me to get a 21p high five prop, but if I try to look by boat weight and length it tells me to get a 16p prop and doesnt even offer the high five option. Seems like a big difference between the two, like something is off. what would you guys recommend and is high five the way to go? also is it really going to hurt my fuel economy?

Thank you very much in advance, awesome forum, spent hours on it reading lots of good info.

any tahoe 195 / 196 owners who experimented with props?

 

[jestor68]

Re: Tahoe 195 150hp optimax prop question

You are getting pretty high(20%)slip numbers with that 21 " prop. What year is the boat/motor? By comparison, my 23 ft (3500 lb) deck boat runs 8% slip numbers using Solas props.

You might check the motor height. You want the AV plate about even with the bottom.

What brand/type/diameter prop is that? I ask because it's not performing well.

A much less expensive aluminum 4 blade prop will serve as well for a fraction of the cost of a high five.

As far as the Merc prop selector's accuracy goes; when I put my boat's numbers in there, it comes out exactly right with weight or current performance.

What you are seeing with the "current performance" thing showing a 21" is that it provides a "window" from(in your case)45-58 mph possible with your pitch and rpm; depending upon what type boat it is. The higher speed represents a low slip, while the lower speed represents a high slip using your gear ratio(1.87).

The pitch numbers you're seeing from the weight portion of 15-16 pitches(with larger diameters) are not unrealistic for a 3561 lb boat powered by a 150 hp. The stern drive version of that boat is usually powered with the 4.3L MPI(220 hp), with the 5.0L (260 hp) optional.

The 16" you mention is a 16" diameter X 16" pitch; big difference. Your 21 is probably less than 14" diameter.

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

What brand/type/diameter prop is that? I ask because it's not performing well.

Its a SS vengeance 48-16318-21 thats why I figured its a 21 pitch but I dont know the diameter, no other numbers on prop.
could it be that the engine is not performing well and not the prop? even though when I was shopping for a deck boat, I was looking at two almost exact same boats with 150optis engines and the other boat seller told me his got 50mph wot, I dont know what prop he had though.

I believe my boat dry weight is about 2200lb becuase on boat test the same boat with a 115 opti is rated at 2100lb, So I figure family in boat and gear I am estimating 3200-3300lb

A much less expensive aluminum 4 blade prop will serve as well for a fraction of the cost of a high five.

What would you recommend?

the mercury prop selector offers the alpha 4 if I try to select by weight, a 15 diameter and 16 pitch. If I try by boat performance it doesnt offer it at all. it only offers stainless steel 4 blade or the high five 5 blade in 21p but 13.25 diameter.
I dont know why it gives me completely different results. I select all around good performance on both options, or should I be selection acceleration? is that what they have for hole shot?

is the alpha 4 a good choice?

Hope this makes sense, I am just confused with all the different options, and yes you are right a $550 high five is pretty steep.

Thanks

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

oh almost forgot, my engine is sitting 3 slots higher then all the way down, but it does look like at some point it was installed all the way down, but someone moved it up. its hard to explain where the av plate is compared to the hull so I attached an image I found online that shows how the very back of the boat the hull is a bit higher and the plate is in line with that, but not with entire boat hull, if you know what I mean. and it does have a small hydrofoil attached that I want to replace with stingray III
Thanks

 

[jestor68]

Re: Tahoe 195 150hp optimax prop question

If you run a straight edge out from the keel(real bottom) with the motor level, the AV plate should be about an inch above the straight edge. My guess is that the motor might need to be lowered a bit to eliminate some of the ventilation caused slippage you are experiencing with the present prop. That's most likely why your boat isn't going 50-52 mph, like it's supposed to.

As an aside, the Vengeance is not that great a prop. It's basically a black max in SS(similar design). It's not meant to be run high, like some other designs are.

When all is said and done, my choice would be a Solas SS HR Titan 4 (14 X 20). # 1553-140-20. That prop will grab water and won't let go. It won't run as fast on the top end, but for water sports it's better suited; producing better acceleration, faster planning, and better speed holding.

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

Thank you I will defiantly try that prop, do you know what I might expect to pay a local dealer to drop the engine a notch?

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

Oh wow, I dont know where I was looking, I was way off, took the boat out today to try it out without the hydrofoil,it performed better, but I didnt see the rpms ever get past 4700rpm. but it was choppy today so wot was 45mph at most. So I am kind of glad I didnt buy the solas 14x20 yet, getting paid friday so I want to order it then, should I drop down to 14 1/4 x 18 ?

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

If you run a straight edge out from the keel(real bottom) with the motor level, the AV plate should be about an inch above the straight edge. My guess is that the motor might need to be lowered a bit to eliminate some of the ventilation caused slippage you are experiencing with the present prop. That's most likely why your boat isn't going 50-52 mph, like it's supposed to.

As an aside, the Vengeance is not that great a prop. It's basically a black max in SS(similar design). It's not meant to be run high, like some other designs are.

When all is said and done, my choice would be a Solas SS HR Titan 4 (14 X 20). # 1553-140-20. That prop will grab water and won't let go. It won't run as fast on the top end, but for water sports it's better suited; producing better acceleration, faster planning, and better speed holding.

Hi, I never did get a chance to get that prop, wasnt sure which one to get since my rpms changed when I took the se300 hydrofoil of the engine can now get trimmed some without ventilating and rpm are much lower, last weekend I was out with family and friends, full boat of people and finally all my gear for fishing installed like trolling motor and 2 more batteries. Boat was running at 4500 rpm and top speed of 41 mph. I even tried wakeboarding and hole shot was slow and slowest plane speed was right at 20. Now I really want to get the Solas titan hr ordered here on iboats while they are on sale just not sure what pitch, does 14-1/4 x 17 seem like a good choice? Thanks

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

Just wanted to share the new prop experience, I did end up buying the solas titan hr 17p here in iboats, took it out to the lake and WOW getting the boat on plane is way faster and easier, I even hauled a 4 person tube with kids and boat jumped on plane in no time. absolutely love it, interesting thing though is that the rpms are still topping out at 4600 rpms and right at about 41mph GPS, I am wondering if my tachometer is showing bad since I dropped to 17p from 21p and rpms stayed the same.

 

[jestor68]

Re: Tahoe 195 150hp optimax prop question

Well, the prop slip calculator shows that with your gear ratio and pitch; using a 10% slip, you are doing 5343 rpm.

Maybe it's time to have the tachometer checked for accuracy.

 

[acuaholic]

Re: Tahoe 195 150hp optimax prop question

Is it actually possible to check a tachometer or do I just buy a new one?

 

[jestor68]

Re: Tahoe 195 150hp optimax prop question

The best thing to do is take it to your Mercury dealer and have then hook up their shop tach to check the difference. They can run the motor up to full rpm and see if your tach is accurate.