NEED Stern LIFT Prop Suggestions

[vroom ZOOM]

Hello

Took my 2008 tuffy 1890 deepV out for a pin on the river out here. Tempest plus 27p, Suzuki DF200, 5600rpm, 12% slip. Motor mounted on the centermost hole. With a few people in the boat, it got up on plane fairly well with the trim full in. At slow speed it was fine, not blowing out or anything, but if I started to trim up it would porpoise. A touch down and it was stable. After speeding up I could trim out quite a bit without porpoising. That was only a short ride though. Decided to take it on a fishing trip, and with four in the boat, a cooler, and the rear livewell filled, that is when the trouble began. On plane a little slower (whadaya expect?) and then with trim full down started speeding up, but now with trim full down it porpoises and I cant speed up, let alone giving any up trim. What mods do I need to do to make this boat stable again?

Thanks

 

[JimS123]

Easy fix - trim tabs.

 

[dingbat]

Every hull is different..
If I put the least little bit of negative trim on my boat is will porpoise wildly... to the point of being almost out of control.

Try not using any negative at all (prop shaft parallel to surface) and see how it behaves. If that doesn't work, tabs should help

With a full load you will have to "hammer" it to et up on plane. Being "light on the throttle" isn't doing you any favors.

 

[vroom ZOOM]

Hello
Question for all the prop gurus.
Many on other forums that are familiar with my type of boat say that I need a stern lift prop. Current prop is a tempest plus 27p turning on a suzuki DF200 at 5600 rpm at WOT. I heard the tempest is a bow lifting prop though. Seems like I need a STERN lifting prop. Any recommendations on a make and model? I will probably go down to a 26p to get the rpm just below the rev limiter. I am fine with either merc or solas or turning point or michigan wheel etc.

 

[alldodge]

All props lift the bow and the stern, the amount depends on hp to weight. More blades will create more stern lift while also lifting the bow. To much lift and porpoising happens

 

[QBhoy]

Couple of things to add perhaps.
The tempest is usually pretty good at lifting the bow and stern. I’ve got a couple and tried on two of my boats. But the main thing I’ve noticed is that they like as much rpm as possible. So you being about 400 rpm short of your rpm range means you have room to play. I’d perhaps think about going down a little in pitch to see what happens. I’d be almost sure you might even gain a little speed too...despite naturally thinking the opposite. More rpm let’s the prop work it’s magic a little better.
I’d also say that the enertia is a hell of a prop too. Have yet to come across a case where it didn’t outperform any other prop it was up against, like for like. But be aware that it’s an odd thing going from a tempest to most other props thinking the usual pitch vs rpm variance rules apply. The Tempest has acted like an inch of pitch above what it actually is...any time I’ve compared it. Just with the big diameter. Although the standard Suzuki stainless props have a huge diameter too.
hope that helps...but I’m quite confident that if you allow more rpm...the more loft you’ll have

 

[Texasmark]

Solace 4 blade SS. Just bought one and it does what it says it does. High quality and in the 13" version, was less than $275 free shipping for my 19P. It does a lot of ventilating at level trim angles just above plane making for high prop slip numbers. Tilt the engine all the way down and arse end stays up while you slow down (bow having increased wetting but your slip numbers get better for you which offsets the added drag. Sounds crazy but it is explained in the ads that it lifts the stern.

The same prop, at mid rpms and level trim....reasonably high slip there too, firewall it, the sucker locks up....a jolt, and trim it out (as high as my engine would lift) and slip dropped to 4%, and MPH was within 2 mph of my 20P Mercury laser at lower RPM....4th blade drag....expected. Mounting height is right on the Crestliner transom, no lift, AV plate below the keel.

Backs off trailer easier with less throttle, and planing out is much smoother. You can hardly notice the Merc. 2+2 transition RPM region when you apply moderate throttle coming out of the hole.

 

[Lowlysubaruguy]

Does it have a bolt on fin installed if so remove it?
what speed is the lowest speed it will occur. Loaded or unloaded or both
if you have an unstable or unsafe porpoise effect happening at speeds say under 40 MPH try a full tank of fuel see if its a weight issue, f that doesn’t change it where is your tank middle back? I’m assuming its under the floor and middle. If its in the rear you probably wont see much of a change

Is this new and if so whats changed or do you even know. Looking at rpms I’m thinking its propped right.

If you move all the weight forward how much of an improvement do you get. if you have people in the boat tinker with there placement to see what kind of weight it takes to make it right.

One fear would be floor is rotted and water logged yet another slim possibility

in a perfect world one should be able to run at max RPMs and speed and have some adjustment in trim left it sounds like you so far off that mark something is wrong.

a picture of the outboard all the way down showing the position between the bottom of the boat and the outboards fins maybe we can tell if its to high. Usually theres other issues when one is way high like cavitation and spraying water

to deep is usually the other way around but thats all a variable with each hull and outboard design.

 

[JimS123]

Does it have a bolt on fin installed if so remove it?

If it doesn't have a fin on now, adding one might help correct the problem. I didn't suggest that in the first place since for your specific issue trim tabs may be the better option.

If you DO have a fin on now, removing it will probably make it worse.

 

[vroom ZOOM]

Does it have a bolt on fin installed if so remove it?
what speed is the lowest speed it will occur. Loaded or unloaded or both
if you have an unstable or unsafe porpoise effect happening at speeds say under 40 MPH try a full tank of fuel see if its a weight issue, f that doesn’t change it where is your tank middle back? I’m assuming its under the floor and middle. If its in the rear you probably wont see much of a change

Is this new and if so whats changed or do you even know. Looking at rpms I’m thinking its propped right.

If you move all the weight forward how much of an improvement do you get. if you have people in the boat tinker with there placement to see what kind of weight it takes to make it right.

One fear would be floor is rotted and water logged yet another slim possibility

in a perfect world one should be able to run at max RPMs and speed and have some adjustment in trim left it sounds like you so far off that mark something is wrong.

a picture of the outboard all the way down showing the position between the bottom of the boat and the outboards fins maybe we can tell if its to high. Usually theres other issues when one is way high like cavitation and spraying water

to deep is usually the other way around but thats all a variable with each hull and outboard design.

The boat can't be rotten, it's a 2008 tuffy and they did not use any wood in the construction of that boat at all. There is no whale tail, I am going to put one on, but I don't see how it would help, since the AV plate is skimming the surface, and the whale tail wouldn't really be in the water? Porpoise happens exactly past 25 mph with a cooler full of food, and 5 people. 25mph is just about it's lowest planing speed at this load. any more and it will porpoise. Today I took it out with little load, and at full trim down I was able to rev it up stable. once it hit 4500rpm I started trimming out and no porpoise, speed went up to 50 MPH stable. I went faster but I wasn't looking at the gps. I also didn't dare trim up higher, it probably has more up trim left and maybe I could ek out some more speed. As soon as i revved down below 4500 at the current trim angle, the porpoise started pretty strong. More weight is making things worse. If it ran the way it runs with a light load I would not grumble at all. Did not really dare to go back and see where the AV plate was in relation to the water. Tomorrow I will put up some pics of the engine mounting arrangement. Trim tabs are the last thing I want to install, I don't want to drill into my boat.

 

[vroom ZOOM]

Aha! Thank you, this is the kind of info I am looking for! And yes, the tempest loves to go full tilt. If I can get my boat out full power past the porpoise... YEEET!

 

[vroom ZOOM]

Couple of things to add perhaps.
The tempest is usually pretty good at lifting the bow and stern. I’ve got a couple and tried on two of my boats. But the main thing I’ve noticed is that they like as much rpm as possible. So you being about 400 rpm short of your rpm range means you have room to play. I’d perhaps think about going down a little in pitch to see what happens. I’d be almost sure you might even gain a little speed too...despite naturally thinking the opposite. More rpm let’s the prop work it’s magic a little better.
I’d also say that the enertia is a hell of a prop too. Have yet to come across a case where it didn’t outperform any other prop it was up against, like for like. But be aware that it’s an odd thing going from a tempest to most other props thinking the usual pitch vs rpm variance rules apply. The Tempest has acted like an inch of pitch above what it actually is...any time I’ve compared it. Just with the big diameter. Although the standard Suzuki stainless props have a huge diameter too.
hope that helps...but I’m quite confident that if you allow more rpm...the more loft you’ll have

LOL, just met a guy at the marina today who said he'll let me try out his 25p tempest. Def give that a shot, but today blazing 50mph in 35 degree weather was - cold.

 

[vroom ZOOM]

ok here are he pictures of the engine full trimmed in, and another of the prop to pad height.

View attachment 329053

 

[vroom ZOOM]

 

[captmello]

that motor looks way too short for your hull. is the boat new to you?

 

[alldodge]

Agree, the ventilation plate look to high, that is unless your aiming for only the bottom of the prop to contact

 

[QBhoy]

Height is set for pretty high performance at that height. Wouldn’t say it is wrong shaft length. It’s a performance hull guys. Has a flat pad on it.

 

[Texasmark]

Height is set for pretty high performance at that height. Wouldn’t say it is wrong shaft length. It’s a performance hull guys. Has a flat pad on it.

Agree on the pad and height could be part of the performance desired. Problem I have is recalling the rule of thumb from the big guns on here, especially a guy from Coral Gables, Fl. I think, with a 300 Johnson on a Donzi I think among other things: 1"up from even per 6 inches of setback.

Using the diameter of the LU gearbox as a quasi reference, if he trimmed out like he was running on that pad just prior to blowing out, he might get a foot of separation indicating a 2" rise in engine height. Looks a lot more like a short shaft on a long shaft transom, or long shaft on a 25" transom. Limited knowledge, but I know of no BBs with a 25" transom mounting position......but like I said....limited knowledge.

 

[QBhoy]

Agree on the pad and height could be part of the performance desired. Problem I have is recalling the rule of thumb from the big guns on here, especially a guy from Coral Gables, Fl. I think, with a 300 Johnson on a Donzi I think among other things: 1"up from even per 6 inches of setback.

Using the diameter of the LU gearbox as a quasi reference, if he trimmed out like he was running on that pad just prior to blowing out, he might get a foot of separation indicating a 2" rise in engine height. Looks a lot more like a short shaft on a long shaft transom, or long shaft on a 25" transom. Limited knowledge, but I know of no BBs with a 25" transom mounting position......but like I said....limited knowledge.

May be right. Hard to tell with the angles engine is at in pictures, but I think 1” up would be a sensible set up for your average speed boat. 2-3” would be high performance and with a pad set up.
Hard to say...but I’m not sure it’s as much as 5” there to suggest it may be a short shaft. Would sure be a rare find to get a short shaft motor like that on a boat. Probably more likely the engine is just high on the transom. Need more pics perhaps ? All the best.

 

[dingbat]

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Seems to be a common problem with that boat

Funny I have seen tons of posts about porpoising tuffys I have the wedges on the hull rev 4 21 p prop tried everything that is supposed to fix it seems like a let down on #tuffy boats behalf very disappointed wish something would work seems like selling it is the next move damn shame

The need for "wedges" is a big hint as to what is going on