Stabilizer

[zachp]

Has anyone had any luck with a stabilizer on their motor? I have a smokercraft 161 with a 80 yamaha 4 stroke and i'm having a problem with porpoising, i have to have the motor trimmed almost all the way ahead to get it to stop, which puts the motor at a forward slanting position which could cause the boat to "push" and in turn i'm not getting optimum performance out of the boat/motor. I have been lookin into installing a stabilizer to see if it would help but would like to hear what others think about them.

[iffwalleyes]

I don't like them. I think they are uncessary. A motor properly trimmed will be at a slightly foward angle.

[ccarlson]

Not true.

There are certain applications where a fin can help improve efficiency, speed and handling performance of a boat.

Some boats just have a tendancy to porpoise and in order to get rid of the porpoising one would have to trim down so far as to make the boat plow, lose efficiency, speed and handling. In some cases, adding a fin can allow the user to trim up significantly further which helps gain speed, control, and makes the boat run more efficiently. It also helps heavier boats stay on plane at lower speeds.

The first thing to check, however, would be to make sure you have a good stainless steel prop that is best fit for your boat and motor combination. You would need to try several types and pitches to see if this helps first. See a good prop shop for help and loaners to try.

I found that going with a 4 blade powertech prop helped me gain control and limited the porpoising more than any other prop for my old Ranger 690 but I still wanted more lift and sustained plane at lower speeds so I added a fin and everything improved greatly. It also eliminated the remainder of the porpoising.

Stabilizer Fins certainly aren't needed for most boats but there are applications where they help.

ccarlson

[dkf]

Don't like fins. But a fin MAY help, if it doesn't your out about $75.00 and 4 holes in your motor. I've found the main cause of porpoising is a poor hull design. My grandfathers smokercraft porpoised and now he has a Mirrocraft that porpoises as well. He could barely trim either boat and it would start bouncing. Never had a Lund do that. One of the best ways to help eliminate the porpoising is to install trim tabs. Trim tabs add more planing surface which helps to stabilize the boat.

[zachp]

Thanks guys,

I think i might try a good stainless 4 blade before i install a fin, the boat calls for a pitch of 17 which i have on there right now, but it's the standard yamaha 3 blade prop. I have not experimented with any other props but am willing to give it a shot. Anyone have any recommendations for what prop to try and if i should go up or down in pitch?

[fishin58]

Hey z.p Are ya stateside now? ya shoulda bought a 2 stroke ..been fishin? the ice is fadin fast! are you goin to be around for opener?, I spose yer goin to URL. not goin to hang with ROGER?

[marine_man]

Quote:

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i have to have the motor trimmed almost all the way ahead to get it to stop, which puts the motor at a forward slanting position

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So, if I'm interpreting you correctly, you're saying that you have to trim the motor up (effectively raising the prop) to correct the porposing problem?

marine_man

[zachp]

F58,

Not stateside yet, another week up on the tundra then i'll be home. I'm still planning on making one more trip up to LOW before the ice is out. I will miss opener this year, i won't be back until the last weekend in may, it sucks to miss opener but the fishing and weather is usually a lot better a couple weeks after opener anyways. BRING THE BUCKET YOU KNOTHEADS.

MM,

I trim the motor almost all the way up so it's at a backward slanting motion much like a back slash \. I worded it incorrectly in my first post. Usually once up on plane i can trim it back a little bit, but not as much as i should be able to.

[marine_man]

So, when you take off from a dead stop, you have the motor trimmed down all the way, correct?

Once you've planed out your raise the trim slowly until the boat porposis and then trim back down a little until it stops?

It sounds to me like you're running your motor trimmed out too far, causing the porposing.. Just about any boat will porpose with the motor trimmed out too far.

marine_man

[CatManLee]

The best thing you could do is get a better prop. Find a nice stainless steel prop with a good "cup" to it. The cupped edge will help hold the water and give a little better bow lift. You would be amazed at what a "good" prop will do for your boat.

Weight is also an issue you need to address. Do you have "a lot" of weight in your boat and where is it located? The more weight you have up front, the harder it is to get the bow to stay up, but too much weight in the rear will make your boat plane slower.

There are too many variables to say for sure, but I'm guessing weight, a normal prop, and only having 80hp are all combining to make this happen.

Start with a prop and go from there.

[zachp]

I start out with the motor trimmed almost all the way down, once i get up on plane i can trim it back a little bit, but very little, and it's not even close to being in the vertical position which is considered "optimum". I'm going to try a couple different props this spring and see if i can get a little more performance out of the motor. I should be getting up in the low 40's with that boat/motor combo but i have yet to get it above 35.

The boat is only 16.5' and it is rated for up to 90hp. There are a few times when i have a lot of weight in it but i have done tests with just me and nothing else but maybe a battery and anchor. I've also had 3 people, a couple coolers, 2 batteries, and if we're lucky 15 gallons in the livewell and a few lbs of fish. It didn't seem to matter what i had in the boat, the results were always the same.

[CatManLee]

One more thing to look at is the height of the motor. Is it set up and mounted in the right holes? I don't know how to help you with that, but it made a difference with my boat.

I have a 1990 17' MirroCraft Ultra Pro fiberglass boat. The hull has a slight angle "up" at the rear 1' of the keel...I guess it's kind of like a pad on a bass boat. The motor is a 1990 90hp Evinrude (boat is rated for 130hp)so I could have more hp, but the cash flow wouldn't allow it. When I had the motor mounted, we put it on the bottom holes (all the way down). It performed all right, but had the exact same problem your talking about with the boat porposing with just the slightest trim. The advice I got from "bass boat guys" was to raise the motor and try it. Well to make the long story a bit shorter, It's now mounted as high as it can go and it performs better. My speed with a 17-pitch aluminum prop went from 34mph to 36mph (under the same conditions) and I could trim out a little more. (but it still proposed fairly easily) My hole shot with this boat is great, so I wanted to get a higher pitch SS prop and see what that would do as far as performance. I got a good cupped Stainless Steel Propeller and tried that...WOW, What a difference. It's not quite as fast on take off (not bad though), but top end and bow lift improved considerably. Top speed (GPS) is now 42-43mph under normal conditions and weight (full of fuel, etc). I have had the boat as fast as 45mph, but 42mph is about the norm now. That's an increase of 6+ mph. It might not sound like a lot, but the boat also handles better, corners better, and the boat doesn't porpose as easily. I also have a nice shiny prop now too! lol. My boat now according to "the calculator" is performing as good as it can with my motor and prop pitch.

I guess what I'm trying to say is try stuff! It's not a lot of fun, and it takes some time, but in the end it will be worth it, because you'll find something that will work. And when you find that "thing" that works, it feels great. Just make sure you pay attention to things like the RPM's and water pumping through the motor, so you don't wreck anything.

Good luck, hope you get it all figured out.