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07-21-2020, 10:23 PM #1Member
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1979 16ft Action Marine - Setup Advice? (Pics)
Hey guys, hoping to get some insight from the great minds on here about what I can do to get more top end and get my stern out of the water more without having my nose at a steep angle. I have a 16ft stub-nose old school Action Marine, powered by a Yamaha 225 Excel with some work done.
Currently my setup is as follows:
-28p Chopper prop
-8" setback using bob's jackplate
-prop about 1/2" above the pad (estimated to the best of my ability with the boat on the trailer @ neutral trim)
-bobs nosecone w/ lwpu
-gas tank all the way at the back
The chopper is nice when I have a passenger and a full tank, but when I'm by myself I don't need all that help lifting the bow. I suspect a cleaver prop would be a better choice in this scenario.
When by myself with 8 gallons of gas, I'm seeing about 70-75mph at most on a windless flat day. The nose is high and light, the boat is doing the chine walk dance, and my hands are busy on the wheel. Engine is at about 6200-6300rpm.
Any advice would be greatly appreciated, want to learn as much as I can. Here are some pics of my setup:
Last edited by reacler; 07-22-2020 at 04:14 AM.
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07-26-2020, 08:39 PM #27000 RPM
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if you can do it raise the motor more. i had a hs vamp with 150 omc and ran 72 with a 21p prop.
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07-30-2020, 01:53 AM #3
Before you go any further I would find a case with a full skeg, that looks scary to me
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07-30-2020, 04:13 PM #4
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08-02-2020, 11:33 PM #5Member
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I havent had a significantly noticeable difference in handling characteristics with this lower vs my old one which had a normal skeg but then again I had a season's gap between driving them. You think it would make a big difference? She gets a little loose in the back when up on the pad when I run it with a cleaver in both cases.
Since starting this thread, I put on a 28p cleaver to do solo runs and I've raised the engine another inch or so and it definitely improved things. No loss in water pressure but have to be careful of blowing out or at least propeller burn when turning at speed. Got her up to 83mph yesterday and had more to go but need more seat time with the cleaver. She also sits level now when up on the pad which feels a lot more comfortable.
Whats the reasoning behind this? I'm just asking because I'm an engineer and studied fluid dynamics, and I was thinking the cleaner less turbulent water would be better especially for a surfacing propeller. How much setback is desirable in my case and how does one determine such a thing?
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08-03-2020, 08:09 AM #6
Clean water is more overrated than Bernie Madoff. With that heavy motor it needs to be closer to the boat to achieve it's natural balance. Those hulls have a ton of bow lift and don't need any assistance from big setback. And that gearcase has got to go. If that little spindly skeg breaks off at speed, you're gonna have a bad day.
Consider this. At a speed of say 85 MPH, how much time does water have to "clean itself up" in the distance of 4 inches?
(85 MPH = 1500 INCHES PER SECOND)Living in the Freedom provided by Bud Conner and his fellow warriors.
R.I.P. my Heathen Brother
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08-03-2020, 10:20 AM #7Member
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Thanks for explaining, it's much appreciated. I may be able to flip and cut my jackplate brackets to reduce setback, I don't want to have to buy a new one. I need a jackplate to get the proper engine height, so cant get rid of it completely.
As for the skeg - while not seen in the pictures, it is quite a bit thicker than a standard skeg. I just measured it with a caliper and its about 0.5" thick at the base, 0.38" at the middle, tapering down to 0.25" near the bottom. I measured my old lower with the standard skeg, and it does not get thicker than 0.34" at any point. I did a rough calculation using the material properties of the aluminum that yamaha uses, and it would take a force of more than 10,000 lbs directed perpendicular to the skeg for the aluminum to start to yield. I was fairly conservative with my calculations too, in reality it should be able to take a decent bit more than that. I feel like if I ever encountered a scenerio where my engine was under that much force, the skeg would be the least of my concern. Only thing I could imagine creating that much force is a sudden impact with an immovable object while turning. Maybe I'm overthinking it but my engineering experience tells me that I should be fine.
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08-03-2020, 11:14 AM #8
Somewhere along the the line, somebody did calculate the PSI exerted on a skeg at high speed. I can't remember what he came up with but it was VERY substantial. The thing to keep in mind is that we're all running basically 20 to 30 or more year old junk that we have no idea of the history. That skeg has probably already had some serious trauma which led to that fancy sculpture you have now, so stress cracking and fatigue becomes a concern.
If I've not scared you to death yet, on the good side with proper setup that boat should easily run 10 MPH faster.Living in the Freedom provided by Bud Conner and his fellow warriors.
R.I.P. my Heathen Brother
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