I/O prop help please

C

CurrentObsession

New Member
Oct 25, 2017
12
Lake St Clair, Michigan
Boat Info
1998 Sea Ray 290 Sundancer
Classic tri-axle trailer
Engines
Twin 5.7 EFI/ Alpha 1
Hello,

New here, this is my first post.

Bought my first Sea Ray late last fall and getting it ready for action soon. It came with very bet up props and outdrives. Getting drives replaced now.

Original Vengeance 14x19 SS props are damaged beyond fixing. That begs the question of is there is now a better prop to use in place of the original? Anyone have experience using something different? Suggestions welcome.

Thanks
Steve
 
Welcome to CSR!

Can't help too much with the prop question, but wanted to welcome you to the forum. Enjoy your new to you boat!
 
Hard to pick a prop without running data - RPM vs speed all up the rpm range.
I suggest you reach out to Ken at prop gods and get a pair of loaners from him based on his recommendation, then swap them out for the right set once you gather some data.

He has a very reasonable fee for loaners.
 
Your best bet is to get a recommendation for a local prop guy and see what he recommends. If you can’t find anyone locally Google PROPMD. I used them for my old boat and they were fantastic.
They’re recommendations were on the money and they had great prices.
 
All good advice above Steve. I'll add a couple of things. You need to prop your boat like it was from the factory for starters. The reason is this: Your motors need to achieve their maximum recommended RPMs at wide open throttle (WOT). I believe that number is 4200-4600 RPMs. If you undersized your props you risk over-revving the motors. If you oversized the props you could not reach the WOT RPMs and you would be "lugging" the engines.

Before you can even check the WOT RPMs you need to make sure the bottom of the boat is free from growth, the engines are properly in tune and running right and that you are not packing around a lot of extra weight. Then try the loaners.

Let us know what you find out.
Shawn
 
The other guys are right in that you need to get some data first, as all boats are different, but I happen to have the exact same boat and power package. We also have the genset, not sure if you do. Anyways, below is a copy/paste from a post I made in the 98 290 thread a few weeks ago. If you want to try some cheap aluminum’s, these props might be a good starting point. Let me know if you have any questions

We have the 5.7 alphas and I run aluminum quicksilver Diamond4's 14x20. I went aluminum last year to see how they performed (they're cheap) and I am very happy with them. We'll probably stay in this boat for a year or two so I'm going to just stick to them but if you went SS you'd probably want to drop the pitch a couple degrees. My WOT is 4600.

Our numbers, fully loaded all gear, 2 adults, 100% water, 100% fuel, no waste, calm day:

7mph 1200RPM
8mph/1600RPM
9mph/2000RPM
24.4mph/3000 (on plane, full tab, drives tucked)
28mph/3400 (this is our preferred cruise, boat is very happy here and only needs minimal tab, drives brought up to lowest mark on the trim gauge)
38-39mph/4600

We dropped a few mph on the top, holeshot is slightly better but she stays up on step much nicer now. slow speed handling is slightly improved too.

Stock should have been Mercury Vengeance 3 blade 19 pitch stainless. I still have ours as backups but we needed to turn 3400+ to stay on plane properly.

The pic of our boat below was taken at about 2900 RPM doing 22-23 mph. If you click the link you can see the wake that we're just barely on plane. That is will full tabs down as well as drives, it's comfortable and the motors sound good but I feel like it's plowing just a bit at that speed
 
Interesting read. I have a 94 300 with 5.7 Alpha Gen II. I've added larger tabs and need to do 3700 do stay on plane. I'm able to back the tabs off a bit though at that rpm. My speed is 24.5-25.6 mph. I've been thinking about changing the props out too.
 
frosh coach said:
Interesting read. I have a 94 300 with 5.7 Alpha Gen II. I've added larger tabs and need to do 3700 do stay on plane. I'm able to back the tabs off a bit though at that rpm. My speed is 24.5-25.6 mph. I've been thinking about changing the props out too.
Click to expand...

What's the size/weight of your boat? Our 290's are 10,500# dry, 10'3" beam. What I don't know is how the dry weight is calculated by sea ray. I've read that 10,5 number would have been minimal options (no ge,ac,etc) and the smallest engine package offered which in our case would be the single 7.4/B3. If that's the case, our boat is significantly heavier than the rating.

I should have mentioned I also added the Bennett Drop fins last year. I can't say for certain how much they helped, since I did the props and fins at the same time.
 
Strecker25 said:
What's the size/weight of your boat? Our 290's are 10,500# dry, 10'3" beam. What I don't know is how the dry weight is calculated by sea ray. I've read that 10,5 number would have been minimal options (no ge,ac,etc) and the smallest engine package offered which in our case would be the single 7.4/B3. If that's the case, our boat is significantly heavier than the rating.

I should have mentioned I also added the Bennett Drop fins last year. I can't say for certain how much they helped, since I did the props and fins at the same time.
Click to expand...
I need to find out what the dry weight is. I also have the drop fins on the larger tabs and a gen set. Are your motors EFI or Carb?
 
frosh coach said:
I need to find out what the dry weight is. I also have the drop fins on the larger tabs and a gen set. Are your motors EFI or Carb?
Click to expand...

Not to completely sidetrack OP's question but I just checked the archives for your boat.

1994 300 DA IO T-5.7L (230 hp) Alpha 1 CR 1.50:1 14 x 19 QSS 4600
8,700# DRY

That being said, you should get detailed data like I have above for your current props and then work with a shop to determine the correct pair for you. Lots of places will do a free exchange so you can dial them in. You should be able to get that boat to plane at much lower revs.
 
Wow
This site doesn't disappoint.

Thanks to everyone so much for the input and especially to (Strecker25) for real world same boat info. I looked for the aluminum props you have but can't find a matching one for counter rotating port side. The guy I consulted locally says they don't make LH aluminum props.
 
CurrentObsession said:
Wow
This site doesn't disappoint.

Thanks to everyone so much for the input and especially to (Strecker25) for real world same boat info. I looked for the aluminum props you have but can't find a matching one for counter rotating port side. The guy I consulted locally says they don't make LH aluminum props.
Click to expand...
Sure they do

Here's the LH on amazon. Oh by the way, if they're "defective" you can send them back for free if you have amazon prime. My first set of 18's over revved past 4800 RPM, so they were "defective" to me ;)

https://www.amazon.com/gp/product/B000XBHQQC/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

oddly enough the RH is out of stock everywhere. It looks like they've replaced the Diamond4 with the Alpha4, supposedly some special mercalloy material. Slightly more expensive, but they're available in both RH and LH at 14x20 as well.

https://www.mercurymarine.com/en/us/propellers/sport-series/alpha-4/
 
Strecker25 said:
Not to completely sidetrack OP's question but I just checked the archives for your boat.

1994 300 DA IO T-5.7L (230 hp) Alpha 1 CR 1.50:1 14 x 19 QSS 4600
8,700# DRY

That being said, you should get detailed data like I have above for your current props and then work with a shop to determine the correct pair for you. Lots of places will do a free exchange so you can dial them in. You should be able to get that boat to plane at much lower revs.
Click to expand...

thank you, time to do info gathering!!!!
 
Update:

Went with these (Quicksilver Diamond 4 blade alum) and so far so good......

Product Quantity Price
QA2186X 14R20
1 $126.08
QA2187X 14L20
1 $126.08
Cart Subtotal: $252.16


Since I am still in the break-in phase (new Alphas) I can't say with absolute certainty, but so far I am very pleased with the performance. She gets out of the hole nicely and cruises at 28 MPH at 3000 rpm.

Thanks everyone for your help
 
Last edited:
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