Fisher sv-19 gt w/ 150EFI prop pitch?

[Bgbbgb246]

I have a 1995 Fisher sv 19 gt. Nadaguides claims my boat has a “net weight” of 1100lbs. Its not clear to me whether this includes the motor dry weight or not.

originally it had a force 120 on it. This force 120 had an aluminum 19p prop. I decided to get rid of the foce and pick up a very reasonably priced 2000 Mercury 150 EFI.(max hp for my boat is 150)

I need to buy a prop for this motor. I do believe my 19p will be under-pitched and will provide no meaningful data for my future prop selection since i will likely hit 6000 rpm before i hit the max rpm with the prop.

I tried to use a prop selector program but using the weight of the boat (1100 without the motor and 1100 with the motor), it tells me that i need a 26p or a 30p respectively which seems unlikely. I think the fact that its an aluminum bass boat throws the calculation off maybe?

So heres my hail mary question. Does anyone have a sv 19 with a 150 on it? What prop do you run? Even if its a different motor manufacturer, the data may be useful.

Let me know if you have any other useful info that i could try to utilize. Im just trying to avoid buying a prop that isnt in the sweet spot for my setup.

 

[merc850]

All you need is a tachometer to show your present rpm then you can go up or down for the right prop - this is really the only way to match your outfit. A tach will also show engine performance, idle, max rpm etc. Any alternator driven one will work

 

[Bgbbgb246]

All you need is a tachometer to show your present rpm then you can go up or down for the right prop - this is really the only way to match your outfit. A tach will also show engine performance, idle, max rpm etc. Any alternator driven one will work

I have a tachometer. My understand is that if i hit the max rpm of the motor (6000rpm) before i hit the max rpm due to the prop, that the test wont mean anything. Because at that point the motor is the rpm limiting factor and not the prop.

From what your saying it sounds like i need a prop that it “over pitched” and then using the tachometer i can figure out how many inches of pitch i should decrease for the prop to put the motor in the sweet spot at wot (which from what i understand is between 5800 and 6000)

 

[merc850]

The prop pitch is right when the motor is at full throttle and the rpms are within the max. eg.If the pitch is too low the motor will exceed the 5800 rpm limit, this is not good.
Put the 19 on it and see what the max rpm you get - but only for a few seconds then note the rpms.
I would say a 25" would be close and if you have a marina near you they might lend you a prop (and advice) to try.
I have a 16' Baja with an 85hp and I'm running a 21" this works well (whereas a 23 is too steep) but I am going to have it "cupped" to gain a little bit more speed.

 

[dingbat]

The advertised weight of an I/O typically includes the motor since it’s an integral part of the boat.

The advertised weight of an outboard powered boat does not include the weight of the motor for obvious reasons.

For prop calculations “weight” includes everything……Passengers, fuel, gear, etc.

 

[QBhoy]

Hi. Is this new motor an efi 4 stroke 150 ? If it is, just a word of caution around the thinking behind you saying 150 is the max rated for the boat. Often guys that have a boat from a certain era where the maker had a 2 stroke engine in mind, when stating max hp. The newest of mercs have come a long way for being very lightweight…but at the age of engine you have (if it’s a 4 stroke)…they were very very heavy compared to perhaps the 150 2 stroke the maker might have had in mind. So a merc 150 2.0 2 stroke is about 170kgs (my black max is anyway). A new merc 150 4 stroke or the older one you mention…will likely be over 200 kgs at least. Make sure that transom is good.
As for the prop. Comparing different engines for prop sizes as a comparison, doesn’t work at all really. All different ratios involved and more.
If you are seeing about 6000 rpm and/or on the limiter, if it’s easily doing that, you’ll need more pitch, as you’ll be aware. I’d throw a cheap black max 21” on there to see what happens. Take it from there. Any good dealer should be able to let you try before you buy, I’d hope. Good luck.

 

[Bgbbgb246]

The advertised weight of an I/O typically includes the motor since it’s an integral part of the boat.

The advertised weight of an outboard powered boat does not include the weight of the motor for obvious reasons.

For prop calculations “weight” includes everything……Passengers, fuel, gear, etc.

Thank you for adding this info. I was very curious about this part. This helps with at least the rough calculations.

 

[Bgbbgb246]

Hi. Is this new motor an efi 4 stroke 150 ? If it is, just a word of caution around the thinking behind you saying 150 is the max rated for the boat. Often guys that have a boat from a certain era where the maker had a 2 stroke engine in mind, when stating max hp. The newest of mercs have come a long way for being very lightweight…but at the age of engine you have (if it’s a 4 stroke)…they were very very heavy compared to perhaps the 150 2 stroke the maker might have had in mind. So a merc 150 2.0 2 stroke is about 170kgs (my black max is anyway). A new merc 150 4 stroke or the older one you mention…will likely be over 200 kgs at least. Make sure that transom is good.
As for the prop. Comparing different engines for prop sizes as a comparison, doesn’t work at all really. All different ratios involved and more.
If you are seeing about 6000 rpm and/or on the limiter, if it’s easily doing that, you’ll need more pitch, as you’ll be aware. I’d throw a cheap black max 21” on there to see what happens. Take it from there. Any good dealer should be able to let you try before you buy, I’d hope. Good luck.

Its a 2 stroke from the same time frame the boat was built. I took the weight into consideration when making a motor decision.

At this point im thinking that i will just try to buy a cheap used 23p or 25p prop to do a water test and then purchase a nice prop from there. I will of course have to take the composition and quality into the calculation when deciding on a final pitch

Also, i discovered that my wot should be between 5000 and 5600. Not that that changes my question but i just didnt want to put bad info out there

 

[Texasmark]

In your water test keep in mind your normal usage. The WOT pitch determination should be made with normal usage weights/loads/type usage (hole shots for water skis/tubes/water toys) and all. When boating at other times, like when you are alone then just adjust the throttle accordingly to stay in RPM range if you don't have a rev limiter to keep you in line.

 

[Faztbullet]

A 21-25 pitch is in the range depending on prop brand