Boat Porpoising Issues

I have a 02 Alumacraft Magnum tiller with a 03 Johnson 60 4 stroke. When I am running WOT and trim the motor up the boat wants to porpoise. Would adding a hydrofoil cure the porpoising problems?

could a few different probs. were you by yourself? could be trimming to much, when boat starts to porpoise just trim down until it stops porpoising little can go a long way. that should be your best top speed. a foil will slow you down some. foils normally are used to get you on plane faster! prop condition &/or correct size? good luck

Prop is a brand new 17 pitch stainless steel michigan wheel. I was running a 19 pitch SST on it but I was not operating in my recommended WOT (4700 rpms to 5300 rpms). I was only getting 4400 to about 4800 rpms depending on conditions and how the motor was trimmed. Now I can hit right around 5000 rpms with the 17 pitch.

Wheres your motor mounted? Most causes of porpoising are running to much pitch of prop, weight distrubution, and motor mounted to low.

The motor was mounted in hole #2. I moved it up a hole and noticed some improvement.

I think the weight disribution is part of the problem. That is a heavy motor and it is a tiller boat so most the weight is in the back.

One solution is to add lead shot bags to the floor of the front compartments. Smaller and less mess then sand bags. Should keep the front down and really helps cut through waves rather then pound them when your solo.

Same boat here. 02′ 165 mag with 93′ yammi 60 2-stroke

Tops out at 30 on a glass day with 2 people. I do have a plate on it but like stated that should only be for hole shot. weather it works or not i dont know my buddy put it on when he owned it.

I only have porpusing issues when over trimmed. drop the motor a bit and it stops. I wouldnt say I have a lot of weight in the front just 1-2 batts for the bow mount.

Feel free to check out the boat on the group “rate my rig” I have lots of pics posted of it. -Mark

I think you’re still over propped. I’m running a 13p stainless on my 03 merc 60 four stroke and I’m getting max rpms of 6000 and 32 to 34mph. Lund 1675 tiller.
See if a dealer will let you borrow a few smaller pitched props to find the match you’re looking for.

The recommended WOT for this particular motor is 4700 to 5300. I hit right around 5000 now so I don’t know that I am over proped, although I was told I should be running pretty close to 5300 rpms for optimal performance. Mabe a 15 pitch would do the trick.

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Same boat here. 02′ 165 mag with 93′ yammi 60 2-stroke
Tops out at 30 on a glass day with 2 people. I do have a plate on it but like stated that should only be for hole shot. weather it works or not i dont know my buddy put it on when he owned it.
I only have porpusing issues when over trimmed. drop the motor a bit and it stops. I wouldnt say I have a lot of weight in the front just 1-2 batts for the bow mount.
Feel free to check out the boat on the group “rate my rig” I have lots of pics posted of it. -Mark

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How large is you trim range? Can you trim it out pretty far before you start to propoise?

I’ve got a Sylvan Backtroller 16 with a 60 HP Merc 2-stroke with a hydrofoil. The front of my boat is real light. When I’m alone, I can’t trim it up much at all or it porpoises quite a bit.

You need to be able to hit your max. Not saying you have to hold it there. If you’re running wot and not at the max rpm’s, you are in a sense lugging the motor.
I’d play with prop size before adding a foil. And I’d be carefull about trimming too far out of the water, even if it doesn’t porpoise on you.

I would assume it is. My hull spray wot is at the rear 1/3 of the boat. Which means she’s up on top with just the rear of the hull making contact with the water.
do you have a lot of bow spray when you get it set notto porpus?

Is your boat maxed out HP wise??? Reason I ask is, if your boat had a console most likely the HP rating would be much higher than a tiller boat. That equates to your boat never really getting up on plane, and that could be made worse due to being even more under HP’ed. First thing like the others said, get your prop pitch down in order to get the most out of your motor-could play with going down in pitch and staying same in diameter (more bite). All depends on how much money you want to spend, but with most tiller boats, other than the hot new technologies, they are never going to be performance machines or speed demons and spending money in that direction is much like dumping a ton of money into your riding lawnmower trying to make that go faster. On the other note, tillers are fishing machines and most guys who own them bought them for that reason alone. If your boat is underpowered and you like your rig, you may want to think about swapping out motors to max out your boat.

good luck!

Jeremy

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I would assume it is. My hull spray wot is at the rear 1/3 of the boat. Which means she’s up on top with just the rear of the hull making contact with the water.
do you have a lot of bow spray when you get it set notto porpus?

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I think the hull spray is mainly off the back of the boat. I will have to pay more attention to that this weekend when I am out. I do hit low 30’s with it. It is really touchy as far as the porpoising issue goes though.

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You need to be able to hit your max. Not saying you have to hold it there. If you’re running wot and not at the max rpm’s, you are in a sense lugging the motor.
I’d play with prop size before adding a foil. And I’d be carefull about trimming too far out of the water, even if it doesn’t porpoise on you.

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That is why I went to the 17 pitch… I was not hitting the WOT range of 4700 to 5300. I was under the impression that as long as you are in that range you are okay, but the closer you get to the top end of the range the better off you are as far as getting the most out of the motor. I would like to try a 15 pitch and see how that works.

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Is your boat maxed out HP wise??? Reason I ask is, if your boat had a console most likely the HP rating would be much higher than a tiller boat. That equates to your boat never really getting up on plane, and that could be made worse due to being even more under HP’ed. First thing like the others said, get your prop pitch down in order to get the most out of your motor-could play with going down in pitch and staying same in diameter (more bite). All depends on how much money you want to spend, but with most tiller boats, other than the hot new technologies, they are never going to be performance machines or speed demons and spending money in that direction is much like dumping a ton of money into your riding lawnmower trying to make that go faster. On the other note, tillers are fishing machines and most guys who own them bought them for that reason alone. If your boat is underpowered and you like your rig, you may want to think about swapping out motors to max out your boat.

good luck!

Jeremy

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Yeah it is maxed out and the console version in the same boat is rated for a 90 I believe. It plans just fine and it is fast enough for me. Low 30’s. I do love the open floor tillers offer and I will take that over speed anyday.

Sounds like propping will eventually get you where you want, along with weight distribution as others have mentioned. Hydrofoils can be feast or famine.

Jeremy

IMO, stainless props are way to heavy for a motor w/ that hp rating. I’d suggest going back to an aluminum w/ a pitch that will max out your rpm’s.

I kindly dissagree. I ran stainless on 15’s, 25’s and 35’s for many years without a problem.
I currently have a stainless 13 on my 60 four stroke and do just fine with me and one other person and all the gear. When I know there will be more of a load in the boat I switch back to my stock aluminum 12 and keep an eye on my rpm’s so I don’t over rev. Everything is good here.

I run a s/s prop on a 25hp motor. No problems.

I agree the problem can probably be cured with a prop change. I’d suggest trying out a 4 blade s/s prop. Typically, you will get better bow lift. That prop will hold the bow up better. Good luck.

-J.

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I run a s/s prop on a 25hp motor. No problems.

I agree the problem can probably be cured with a prop change. I’d suggest trying out a 4 blade s/s prop. Typically, you will get better bow lift. That prop will hold the bow up better. Good luck.

-J.

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Hi Jon. When going to a 4 blade a guy would want to go down a couple inches in pitch to keep the rpm’s up right?

Let me start by saying I’m not a big fan of Michigan Wheel props. Find a local dealer that has demo props for Johnson motors. Start with the same pitch and go down from there. The other factor to keep in mind. Many 4 blade props have a slightly smaller diameter. So the blade surface of a 4 blade is not much different than a 3 blade of the same pitch.

What you will give up in top speed you will make up for bow lift and better hook up in turns.

One question. Is 60hp max for that boat? If not, you may throw a lot of money at the problem and never get any noticeable results.

-J.

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Let me start by saying I’m not a big fan of Michigan Wheel props. Find a local dealer that has demo props for Johnson motors. Start with the same pitch and go down from there. The other factor to keep in mind. Many 4 blade props have a slightly smaller diameter. So the blade surface of a 4 blade is not much different than a 3 blade of the same pitch.

What you will give up in top speed you will make up for bow lift and better hook up in turns.

One question. Is 60hp max for that boat? If not, you may throw a lot of money at the problem and never get any noticeable results.

-J.

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Yeah it is the max horse power since it is the tiller version. The console version is rated for a 90.