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Need Prop Input Sea Pro 21

Old 09-21-2020, 06:17 PM
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Default Need Prop Input Sea Pro 21

Running a Yammy 150 2stroke, currently with an unknown 3 blade aluminum prop and only getting to 4200RPM.
Would like to move to a 4 blade, but any suggestions welcome.
Old 09-21-2020, 07:05 PM
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Gonna need more info, including:

What prop is on there now. Don’t know? Go take a look. Take a photo, post it.

What year & model is the Yamaha 150 HP two stroke?

How fast is the boat going at 4200 RPM?

Why do you want a four blade?

Did you buy this boat recently? I’m guessing so.
Old 09-21-2020, 07:32 PM
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Yammy 150TXRA
Not sure on speed
I'll post a prop photo, but its aluminum and in rough shape.

4 blade to reduce the bow lift he's seeing. The boat doesn't have trim tabs

Posting for a friend who did get the boat recently.
Old 09-22-2020, 08:46 AM
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You have to get the motor running properly before you (he) can play with props.
Old 09-22-2020, 12:30 PM
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Originally Posted by Tom W Clark View Post
You have to get the motor running properly before you (he) can play with props.
The motor is running fine.
It seems as if he is currently overpropped.
Old 09-22-2020, 03:11 PM
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Running a 14.5 x 19 prop
Speed at 4200 is around 40mph
Old 09-22-2020, 04:41 PM
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Originally Posted by Srbenda View Post
Running a 14.5 x 19 prop
Speed at 4200 is around 40mph

You sure those numbers are right? WOT is 4200 at 40 MPH?

Thats NEGATIVE 6 percent slip.
Old 09-22-2020, 05:43 PM
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Originally Posted by Srbenda View Post
The motor is running fine.
It seems as if he is currently overpropped.
Nope. There are at least two of these threads every week. New boat owner, gets around to running it WOT and the boat doesn’t seem as fast as it should, or doesn’t hit the recommended RPM. Their conclusion? It must be the prop.

As if the boat had been used for 10, 20, or 30 years overpropped by 1300 RPM.

Trust me, have the motor looked at. It may be running on only five or four cylinders, may have a clogged fuel pump, restricted fuel hose, who knows. But the fact an outboard starts on runs “fine” does not prove a thing. You might be surprised how well a V-6 runs with only four cylinders firing.
Old 09-22-2020, 05:47 PM
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40 MPH @ 4200 RPM with a 19” pitch prop is about 1 percent calculated propeller slip. Not likely with a damaged aluminum prop. This begs the question: Is the tachometer calibrated correctly?
Old 09-23-2020, 07:02 AM
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Originally Posted by Tom W Clark View Post
40 MPH @ 4200 RPM with a 19” pitch prop is about 1 percent calculated propeller slip. Not likely with a damaged aluminum prop. This begs the question: Is the tachometer calibrated correctly?
Quite possibly its wrong.
He's been suggested to run a 14x18 prop, and he needs to buy something stainless, so I'm trying to help him end up with the right prop.
Old 09-23-2020, 08:27 AM
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Is this a bay boat or a CC ?.
Old 09-23-2020, 08:27 AM
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There a lot more to propeller selection than just diameter, pitch, and number of blades.

At this point, with vague and suspect data, and missing information, no useful recommendations can be made.
Old 09-23-2020, 08:27 AM
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Originally Posted by Gnrphil View Post
Is this a bay boat or a CC ?.
Bay Boat hull
Likes:
Old 09-23-2020, 10:09 AM
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The boat is actually a ‘02 Sea Pro SV 2100 cc bay boat and it has a Yam 150 2 stroke model 150txra, the numbers given were prior to the prop issue, it had no problem coming up on plane and was running 41 mph (gps) at 42-4300 rpm (haven’t had the tach calibrated and not certain of accuracy however it is responsive, doesn’t lag and seems to track with throttle)

I know the prop is spun because my last trip out it wouldn’t come up on plane, had a list to port when I tried to ease into giving it throttle that pretty much resulted in higher rpm and more cavitation, so I had to limp it back to the dock at an idle.

I have replaced plugs myself, had NGK br8hs-10 in it when I got the boat, OEM recommends NGK br7hs-10 so that’s what I went back with gapped at .040. No oil residue or wet plugs when I looked at them after pulling it in, so no indications of dead cylinders. Upon purchase had compression checked and all cylinders ranged between 124-128.

As far as fuel system issues nothing noticeable, I run ethanol free marine fuel and have run sea foam through the first 50 gallons of fuel and use ring free with every fill up since. I have used Quicksilver 2 stroke oil but might look at changing that as I have had other recommendations for Yamaha.

i don’t know if it’s over propped or under propped because you can barely make out the stamped numbers, with the purchase of any used boat you don’t know what is oem and what was replaced.

Oem recommendations vary so was hoping to get feedback

Just trying to get some feedback as to experiences with different setups as I have to replace prop anyway might as well do it right and get something that others have used and performs well.

hopefully that enough information to give useful feedback
Old 09-23-2020, 11:19 AM
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For a Yamaha two stroke 150 to go 41-42 MPH, it will need a 17 ish pitch prop. For the application, there are a number of good stainless three blades out there.

I just picked up a 14” x 17” Vengeance from the prop shop after a ding repair. Like new, and it’s looking for a new home...
Old 09-23-2020, 11:19 AM
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Given the extremely low slip, I bet its a cheap Solas prop on there now. Their props are always steeper in pitch than what the label says. So your 19 pitch Solas is probably closer to 21 in real life.

Id start with a 17 pitch Black Max. Cheap prop with good all around performance. Buy a stainless prop down the road if you really want to dial things in.
Old 09-23-2020, 11:23 AM
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...also consider a 14-1/4” x 17” Yamaha Turbo 1, 14-1/2” x 17” Mercury Enertia / Quicksilver Q3, or a 13-3/4” x 17” Yamaha Painted Stainless Steel.
Old 09-23-2020, 04:36 PM
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Originally Posted by ElcapitanJimmyb View Post
The boat is actually a ‘02 Sea Pro SV 2100 cc bay boat and it has a Yam 150 2 stroke model 150txra, the numbers given were prior to the prop issue, it had no problem coming up on plane and was running 41 mph (gps) at 42-4300 rpm (haven’t had the tach calibrated and not certain of accuracy however it is responsive, doesn’t lag and seems to track with throttle)

I know the prop is spun because my last trip out it wouldn’t come up on plane, had a list to port when I tried to ease into giving it throttle that pretty much resulted in higher rpm and more cavitation, so I had to limp it back to the dock at an idle.

I have replaced plugs myself, had NGK br8hs-10 in it when I got the boat, OEM recommends NGK br7hs-10 so that’s what I went back with gapped at .040. No oil residue or wet plugs when I looked at them after pulling it in, so no indications of dead cylinders. Upon purchase had compression checked and all cylinders ranged between 124-128.

As far as fuel system issues nothing noticeable, I run ethanol free marine fuel and have run sea foam through the first 50 gallons of fuel and use ring free with every fill up since. I have used Quicksilver 2 stroke oil but might look at changing that as I have had other recommendations for Yamaha.

i don’t know if it’s over propped or under propped because you can barely make out the stamped numbers, with the purchase of any used boat you don’t know what is oem and what was replaced.

Oem recommendations vary so was hoping to get feedback

Just trying to get some feedback as to experiences with different setups as I have to replace prop anyway might as well do it right and get something that others have used and performs well.

hopefully that enough information to give useful feedback
A 21 Sea pro doing 41 mph at those RPMS is no slip at all. . Your gauge seems to be off. That boat with a 150 and no top is good for around 45 . Thats everything perfect. Been noted on here before on THT and other sites with people with the same boat.

Its not a fast hull.


at 45 MPH at 5500 rpms which is what the motor is rated for. With a 19 pitch is 15 percent slip. But you getting no slip at 4200 rpms. Very interesting.

Last edited by captain28570; 09-23-2020 at 04:54 PM.

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