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Posts: 626
Location: Madison, WI | Boat - Ranger 618vs
Motor - 2021 Mercury 115 fourstroke
Motor is mounted one hole up. Have a Solas 3 blade stainless 13x19. Hole shot is ok with one guy, so so with 2. Top speed is 47 on gps. Boat likes to porpoise is trimmed up much and any chop on the water. Rpm’s are around 6k at WOT. Tried a Solas stainless 4 blade 13 1/4x15 hoping for better hole shot and less porpoising, but rpm’s max out at 6300 and speed barely touched 39-40. Hole shot was not significantly better. I’m thinking of trying a 17 pitch, but wondering if 13 is the best diameter or should I go up to 14? Of the two props, the 13x19 performs much better |
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Posts: 2237
Location: SE, WI. | I had the 13x19 on my Ex 681 with an Etec 115. Was happy with it!
JD
Edited by jdsplasher 5/29/2022 1:58 PM
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Posts: 297
Location: Not where I want to be! | Unfortunately porpoising is inherent it that hull. You'll need to keep the motor tucked in. That hull also seems to run best at around 40 mph. I found that a 4 blade prop will work the best on that boat. Contact Marks High Performance Props in Indiana. He sells a 4 blade, (Razor 4XL I think) that should work nicely. 317-398-9294 |
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Posts: 596
Location: Duluth | What is max RPM with Solas 3 blade?
Honestly calling a company like the one mentioned above or simply filling out a detailed RFQ on Generalpropeller's website will yeild the correct prop for you. Props are black magic, let the pros handle it.
Edited by CincySkeez 6/4/2022 4:09 PM
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Posts: 3472
Location: Elk River, Minnesota | Hiya!!
Couple of thoughts to consider.
First, since the motor is only 1 bolt hole off the transom, move it up two more holes. this will do a couple of things for you: First, you will be able to obtain more RPMs at full throttle as you will inherently be introducing a touch more slip to the prop, but that extra rpm will also allow the motor to keep the bow up better while at speed. You will also see less bow rise on hole shot as well, which is a nice thing as well.
The next thing I am interested in is the model of propeller you are running from Solas. your RPM max for your motor is 6000 so you are right in the ballpark, so the propeller design might have a bunch to do with your porpoising issues. My gut instinct says you need more rake and more tip cupping to help hold the bow up better.
Suggestion: If you have access to a prop shop, have them take a look at the prop and possibly add a little more tip cupping to the prop. They may also suggest adding trailing edge cupping as well, which will help lift the entire boat out of the water as well. This will give the prop more bite overall, but the trade-off is lower RPM. So... raise the motor up to the highest position it can go.
My gut also says the prop is probably not vented, so another suggestion would be is to have the shop drill vent holes that are about 1/4" or 3/8" in diameter. This will help hole shot as the prop will spin up to a higher rpm before the blades catch.
If you would prefer NOT to have all that work done (and I could fully understand that...especially if you can find a prop that has all the characteristics mentioned above), Then start with just raising the motor 2 holes and test the prop from there.
My gut says the pin for the lowest trim setting is in the correct position, but it might be worth checking. For any boat that has power trim/tilt, the pin should be in the lowest possible position to allow the motor to tuck in so the prop is actually pointed downward to lift the stern out of the water on hole shot. If it is not in this position, that might explain the lack of trim capability the boat has as well as the motor is already trimmed up a touch from it's lowest possible position.
One last thought.... I am not completely sure of the entire layout of the 618, but am guessing the fuel tank is below your feet rather than in the bow like the 617 was built in the early 2000's. If the tank is up front, the boat will always run flat on the water, but should run quite nicely, and you should be able to get the side-spray toward the rear of the boat at full throttle.
I've not been on here much lately, but I'm still around and reading here and there... I'll help out where I can. If you are near the twin cities, I'll even meet up with you if you'd like....we can team it...
Steve |
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