Cured the porpoising issue... Well almost. (Prop question)

[Moose-Hunter]

Sounds like you're very close to having the right set up for that boat! Testing props is a pain, and fun at the same time. Plus it is an education.( trust me on this! ) If and when you get a new/different rig you will have a much better idea of what you need and how to achieve it. The chatter with the four blade sounds suspicious! I went thru the testing process years ago with my 18 ft. ranger with a 175, and settled on a four blade. No chatter at any speeeds that i can remember! You will also have alot of satisfaction once you achieve the performance you want every time you're on the water.

IMHO...

The chatter induced by this specific four blade, was due to, partially, the hub design and mostly due to the simple fact it had four blades. The hub was of the hard plastic square insert design that "fit", but must have had a bit of play under loading. As far as the four blades... Here's my take...

As with any prop, it's a roll of the dice what works for any given boat/engine. Even more so with a four bladed prop. Due to it's design, every 90* there are two blades shielded from the direct water flow. One by the skeg, the other by the drive shaft housing. That's 50% of the blade surface for those keeping score. This situation of being "in and out" of the water pressure brings out ANY prop, hub or diveline play and amplifes it. With my engine, there was a v-e-r-y small bit of "in and out" play in the prop shaft. Probably less than a millimeter. Add in any additional varibles such as a loose hub assembly in the prop, and you can see what would happen.

As not all props are created equal, the same goes for engines. Some react well to four bladed props... Some do not. Mine didn't like this specific prop thats for sure.

Ever try your favorite handloaded ammo is someone elses gun? Same kind of deal. Just a bit wetter.

I'm not a prop expert by any definition. Nor did I stay at that one hotel last night.

[delmuts]

"I'm not a prop expert by any definition."

No! But you're learning!

[311Hemi]

Moose Hunter- who did you work with to get your props from for the testing. I have looked and had a hard time finding someone who will help out. You had someone great to work with. Even if you can just fire me a phone number that would be great.

Thanks

Steve

I worked with PropMD in Eden Prairie when I was testing props. It took me a 3-4 trips out there to exchange props a few times but I finally got her dialed in. No problems swapping out for another prop as long as it wasn't dinged up.

[Moose-Hunter]

After a long wait... I'm sorry to say the last prop test did NOT prove to be the end-all of props for my rig. After close examination, the prop that was delivered was not inline with their advertised specs. The cupping was WAY too extreme and the overall diameter was off as well. The part number was right, but not the prop.

I tested it anyway... not a real barn burner but a little closer than most I've already tried. This one was "supposed to be" a 14.25"x18 with "modest" rake and cupping. This one had very "hard wall" type cupping and a "extreme" rake... I was able to spin this one to about 5700 rpm. Average top end at WOT was 45.5mph. BUT... and this was an eye opener... Due to the additional rake and radical cupping, my little friend Flipper returned. YEP... The porpoising came back just from a prop swap!!! I never would have believed it if I hadn't been at the helm. Needless to say, this one is going back as well. And the WHOLE process may start over AGAIN!

Been doing a far amount of research on my Yamaha engine and the hull design of my boat. Seems there may be some details typical riggers sometimes overlook. Most will rig a boat as dictated by the manufacturers. However... in the real world, sometimes "one size fits all" rigging just doesn't work for everyone. Not wanting to possibly steer anyone astray... That's all I'll say on that for the time being. It's not some super secret factory racing stuff... In fact, it's hiding in plain sight.

I should know MUCH more by late Thursday or Friday...

[propster]

Hey Moose Hunter, you seem to have a pretty good handle on this stuff, and thought I'd ask you a question about props and porpoising. We bought a '95 Ranger 690 vs with a 150 Merc. Has a 9.9 kicker on it, single console, 40 gallon gas tank under the front deck. Anyway, it came with 3 blade ss prop, not sure of the pitch or anything. Speed was okay at 50 or just a hair over, but hole shot sucked. Friend of ours had the same motor on a Lund and had gone through a whole bunch of props testing for the best fit, and wound up keeping one of them, which was a Trophy Hi 5 I think, which he said was the second place finisher on his. Said we were welcome to try it out. So we did, and hole shot was beautiful and gained to about 53-54 top end. That was good for two years, but just this year we started to see the porpoising at lower speeds (23-30 mph), where it hadn't done that before. Haven't really changed anything, and don't want to put it down every time to even it out. Any ideas?

[Moose-Hunter]

Hey Moose Hunter, you seem to have a pretty good handle on this stuff, and thought I'd ask you a question about props and porpoising. We bought a '95 Ranger 690 vs with a 150 Merc. Has a 9.9 kicker on it, single console, 40 gallon gas tank under the front deck. Anyway, it came with 3 blade ss prop, not sure of the pitch or anything. Speed was okay at 50 or just a hair over, but hole shot sucked. Friend of ours had the same motor on a Lund and had gone through a whole bunch of props testing for the best fit, and wound up keeping one of them, which was a Trophy Hi 5 I think, which he said was the second place finisher on his. Said we were welcome to try it out. So we did, and hole shot was beautiful and gained to about 53-54 top end. That was good for two years, but just this year we started to see the porpoising at lower speeds (23-30 mph), where it hadn't done that before. Haven't really changed anything, and don't want to put it down every time to even it out. Any ideas?

Wow propster... Thanks for the vote of confidence but I'm really no expert. But I'll give you a slightly educated guess...

DISCLAIMER-----> IN MY HUMBLE OPINION <-----DISCLAMER

Something changed. As simple as it sounds, If for no "real" reason flipper shows up, something on your boat has changed. Have you added any equipment? Moved anything around? Swapped or replaced anything in the bow or stern? Any new type 31 batteries where smaller batts once were? Is the transom still good? No flexing? Or... Heaven forbid, are you taking on water? Is there any hull damage?

Hot weather and hot water can play tricks on you as far as performance. Typically things will get lower in the water, slower top end and tougher coming out of the hole. Could be just the extreme temps we've been having.

A long shot would be cup erosion on the prop itself. But with the High-5 have so many blades, that thing must grip the water like a bear trap!

If your boat is the same as before, then it could also be engine performance. Again, hot humid weather can kill hole shot as well as top end power. Easily seeing drops of 200 to 400rpm. Finicky two strokers may see even more.

Could be any number of things alone or in combination. Best advice I can give you is K.I.S.S.! Take you boat "back" to the configuration where you had the most performance and build up from there. ONE step at a time.

I hope something I typed helps you out even a little. If not... my bad. And I'll go lay by my dish.

[propster]

Hey, no layin by your dish required. Thought of all those things you mentioned, and answer is no, it's identical, other than I've added a couple pounds Didn't think there was a mystery cause, but thought I'd ask. Hole shot is still great, top end is still great, Prop was refurbished last year and not a nick since, so I'm a little baffled. Need to either keep more gas in the tank than I used to or sit up front!

[marine_man]

Are your engine RPM's running to the same level at WOT?

marine_man

[BoxMN]

Hey propster, it was an Alumcraft not a Lund!! haha!

When you say you refurbished the prop, you sure that wasn't it?

I sure would think the first thing might be even a bit more weight in back might add some hopping if you were on the cusp. Or maybe you are just cruising at slightly less throttle this year?...

I think you should test out a Tempest 19 or 21 on your rig sometime when you get flush with ca$h , I bet you would get same handling and hole shot and more speed out of it, and your motor might spin the 21 better than ours did, we were a bit too low, so went with teh 19 Tempest. But the hi-5 definitely "handles" better and bites better, but no reverse power.

ps, have been shooting the bow, but not as much as I had planned, been too darn hot up there. With cool weather going to get regular again.

[propster]

Hey Box. No, we dinged the prop in Canada the first year after we bought it from you, fixed it right away and the boat's been good for 2 years until just this year. Marine Man, never paid attention to the RPM's back then (or now), so wouldn't be able to compare.

[leech~~]

Porpoising is not always a prop issue. Some times it's just having the motor trim right. When ever I trim up to high or to far out it starts but if I trim the motor in or down a bit it goes away. If you fish a busy lake with a lot of boats. Watch how other peoples boats are riding and see where they have their motor trimmed. Many times I've seen guys having porpoising issues or just a planing issue and you can see that they have their motor trimmed to far up. One guy was having all kinds of issues planing out, his nose was riding way up and he was going no where. He would stop and try it again and a again "new boat owner" I think. I felt sorry for the guy and went over to him after watching this all over the lake for a 1/2hr and told him to try his motor full in when he takes off and then trim it out as he gets up speed. He tried it and it worked but he never came back to say thanks! Just my

[weld1]

after 5 years i finally cured my porpoise issue, its a trophy 180 with a F150 yamaha, i even had the boat back at alumacraft for a week and they told me it was fine! it seems the dealer i bought it from in st cloud on hwy 10 a couple miles south of town (needless to say but i will never buy here again), mounted the motor all the way down in the first hole, after years of research (i feel like a [PoorWordUsage]) i noticed every combo i looked at was in the second hole! alumacraft web site even says they tested in the second hole, so i got out the cherry picker and moved it one hole.....its like a new boat!! i should have left it as the wife says she was about ready to tell me to get a new boat!! o well, i hope this note helps someone in the future!

[Moose-Hunter]

after 5 years i finally cured my porpoise issue, its a trophy 180 with a F150 yamaha, i even had the boat back at alumacraft for a week and they told me it was fine! it seems the dealer i bought it from in st cloud on hwy 10 a couple miles south of town (needless to say but i will never buy here again), mounted the motor all the way down in the first hole, after years of research (i feel like a [PoorWordUsage]) i noticed every combo i looked at was in the second hole! alumacraft web site even says they tested in the second hole, so i got out the cherry picker and moved it one hole.....its like a new boat!! i should have left it as the wife says she was about ready to tell me to get a new boat!! o well, i hope this note helps someone in the future!

Hey weld1... If you have a cherry picker... SERIOUSLY... Try the third hole down! I just tried it today and for the second time during this project, I too have a NEW boat!

Performance gains in every aspect of operation! From low speed planning to WOT! With a Reliance Series 19 pitch prop, I'm now hitting over 50mph at about 5800rpm. Do the math. The prop slip is next to nothing! And it feels as there is more performance to be had!

And... Unless I REALLY crank the wheel at high speeds, the prop will not blow out. As said, I'm on the third hole down and it's gonna stay there until I get a chance to test out on B-I-G water, such as Superior or Michigan.

Raising the engine is such an easy mod, I'm slapping myself silly for not doing it first. THEN playing the "musical props" game.

[weld1]

thanks for the info, please let us know how it tests out!

[delcecchi]

Where did the anti-ventilation plate end up relative to the bottom of the boat? My dealer says it should be even. I'm wondering if this is true.

[Moose-Hunter]

Where did the anti-ventilation plate end up relative to the bottom of the boat? My dealer says it should be even. I'm wondering if this is true.

Hi Del...

The anti-cav plate, with the trim all the way in, is now around 1" HIGHER than the bottom of the hull. If you were to trim the engine back so the anti-cav plate was parallel to the bottom plane of the hull, we're looking at only a half inch HIGHER. As the engine tilts back, the angle of the anti-cav plate becomes less and less until it becomes parellel to the hull.

My guess is that dealers as well as factory trained techs usually go with the factory recommended spec. With Alumacraft, that was mounting the engine in the second hole. HOWEVER... That is for "most" set ups and NOT for individual, boat specific set ups.

Like my boat has a kicker. The factory spec doesn't account for that. Nor did it account for the remote gear for my kicker. To say nothing for the weight added by the shaft/housing "extension" on my F150.

Again, my GUESS, is that the lower unit was too submerged and caused a ton of drag. The engine's torque would pick up the boat, but the drag induced by the deep lower unit set it right back down again. With the hull gripping and releasing... Here's Flipper!! The porpoising took over and the performance was shot.

So far, the difference has been like night and day. Seriously, I have the boat I thought I bought in the first place. I may need a prop with a bit more cupping to the blades than my stock Yamaha Reliance has. But... So far I'm REALLY lovin' what found.

Hmmm.... I wonder what would happen if I went up another hole?

MUhahahahaha!!

[delcecchi]

Maybe you have discovered why the guys from bass and walleye boats, may it rest in peace, were so in love with jack plates.

I just bought, well in the spring I bought, a new motor for my pro vee (suzuki 140) and it, like the 115 merc it replaced, was mounted all the way down.

Now you have me wondering......

[Moose-Hunter]

Maybe you have discovered why the guys from bass and walleye boats, may it rest in peace, were so in love with jack plates.

I just bought, well in the spring I bought, a new motor for my pro vee (suzuki 140) and it, like the 115 merc it replaced, was mounted all the way down.

Now you have me wondering......

If I could run a jack plate, it would already be installed. Too bad it would void my warranty. So no jack plate for me. From what I've been told, at least three of the tin boat biggies will void your warranty in a heartbeat if you throw one on.

The only way to tell if your rig will benefit from lifting the engine is to just do it. You'll know right away if it worked or not. On this boat, it was well worth the effort. On my last boat, after the engine was raised, the prop blew out immediately when I hit the gas. Anything above a fast idle was worthless.

If you has access to a good strong hoist and have a tube of sealant handy... Give it a shot.

[delcecchi]

How does one hook onto the motor? Is there some place to screw an eyebolt? Or are straps the answer?

[hydro]

It sounds like you guys are making good progress! I have found that when you push a boat into higher speeds (about 45mph and up) the gear case drag becomes a significant factor in performance. When I got my current boat it was sluggish out of the hole, torque steered terribly, and only made 56 mph on the speedometer. I knew that some setup work was needed.

Since I have a manual jackplate, I measured the prop shaft relative to the bottom of the boat and found that it was sitting 5 ½” down, which was just too deep for my setup. I raised the motor ½” at a time and did test runs until I had blow out on take off and in turns, watching the water pressure on each run. I now run a prop depth of 3 ½” below the pad with the top water inlet holes plugged and am very happy with the setup. Hole shot is good, handling is light and accurate and my top speed increased by 6 mph (again on the speedometer). I am running a 23” Tempest plus with the vents tuned for the setup.

As far as the setting for the anti ventilation plate, I believe that this is primarily a factor in boats running at lower speeds where gear case drag is not a major factor. In my setup, it is several inches out of the water at speed. It all depends on the hull profile, the boat speed, and the intended use as to where the motor is set, but it should be as high as practical for each setup to reduce unnecessary drag. The right setup wil free up some speed on the top end and also give better fuel economy!

FYI, this is the boat I referred to above.

[Moose-Hunter]

How does one hook onto the motor? Is there some place to screw an eyebolt? Or are straps the answer?

Lifting points are manufacturer specific. On my Yamaha, there are two "loops" already bolted to the top of the engine. A chain conntected between them was my lifting point. I've heard other engines need straps and others need a special "eye" attachment you get from the dealer.

If you can get a hold of your engine's rigging guide (they all have them) it's a big help! Or... Just call a dealer and ask what's required.

Hydro...

Nice ride, my friend! VERY nice!! UNIQUE to say the least!!

I know Coral still makes skiffs and bay boats, but none like yours anymore. Which model is it? Okay... More specific than "the super cool model"... LOL!!

[hydro]

Moose-Hunter,

Thanks for the comment. Unfortunately the boat I have is no longer made and the manufacturer, Viper Boats, is no more. They were a bass boat company in northern Arkansas and went under about 5 years ago. I guess I'll just have to take care of this one;)

[Moose-Hunter]

Bringing this back around for reference...