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How to make boat faster?


Majestic

Question

My boat seems beyond slow, it's kind of expected because the motor is a 30HP Honda 4 stroke and the boat is a 16 and a half foot Lund Rebel SS. It seems like it should be faster then what it is though.

I'm guessing I only can go about 10-12 MPH when I'm WOT. It doesn't seem like my boat and motor are in unison. I play around with the tilt but it doesn't seem to change much.

I researched this one late night awhile back and found a thread where some guy had a 4 stroke that was really slow on his boat and he added something to his boat and said it was like adding an extra 10HP, it was much faster.

Problem is I can't find that thread or remember what they were talking about lol.

Any suggestions? Thanks

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Here are some real world numbers. Merc 4 stroke 30 = 172#, Yamaha 4stroke 25= 168-178# Honda 4stroke 30 = 155/160# The ranges are based on different shaft lengths. So much for the old "honda is heavier" banter.

Oh, and the 2 stroke Evinrude Etec 30 is 156# for the 20" shaft. Thats a whole 4# lighter than the Honda 20".

The fact is that the boat is underpowered, no matter what 30hp is on the back. The 1999 catalog lists the dry weight of the boat at 675#, with a max Hp rating of 50. My '97 Explorer was 615# and rated for a 45, but I still got gps speeds of 26+ mph, so I would think that he should be able to get in to the 22 or so range.

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Finally found it! It was on a different forum I'll just post what was said here.

One thing you can do inexpensively that will help your hole shot is to add trim tabs. No need to buy them from cabelas/westmarine; go to TrueValue and buy a 48" piece of 2" aluminum L-angle. Cut it to fit your boat and silicone it in place. Let it cure for a few days, then test it. If it gives you what you need, then silicone/screw/bolt it in place.

I had a similar situation with a 25hp tiller on a 40hp rated hull. Could not get the boat to plane with any setting. Added about 80 sq inches of tab this way. Put me back in the middle of my pin range. Simple fix. Didn't even have to remove any transducers. I get so much hole shot now, i even wish I'd only put 1/2 as much on.

trim tabs: i glued mine on the back of the transom at the plane line to extend the 'bottom' of the boat an additional 80 sq in. i was amazed at the impact. it was like adding 15hp.

fins: will help also and can be used in combo. they will knock a bit off the WOT speed and gas consumption, but it's not significant to me.

Conceptually, it's like adding pods to the back of your boat like the mud motor boys do. Puts your mass further forward on the planing surface, i.e. easier to come up and out. For $20 it was a pretty phenomenal impact.

Has anyone out there done this?

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Too many cooks in this kitchen...

Majestic... You have a set up problem. No doubt about it. Throwing cash or snake oil cures at it won't do what you need done. The other experts here seem to have a good handle on things so I'll bow out and wait for the outcome.

And as far as the "80 inch aluminum angle trim tab" thing... That would NEVER happen on any of my boats. Not even with a gun to my head. IMHO... A waste of a nice piece of aluminum stock.

Any job great or small, do it right or not at all.

Edit: Check out the Honda site for specs and info on your engine. Pay close attention to the changing pictures at the top of the page. that is a Rebel, isn't it?

http://marine.honda.com/outboards/motor-detail/BF30

Best of luck on your project.

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Agreed Moose! That boat should be getting high teens low 20's if setup properly. I had a HEAVY 1983 16ft Lund with a 25hp Merc tiller and could get up on plane easily and top out around 25mph with just me in it. If I added anymore weight (extra person, fill livewell, etc.) the performance suffered greatly and could hardly get up on plane.

First, easiest, and cheapest thing to check is make sure you have everything setup properly. You may also want to get someone to check it out for you, they may be able to notice or figure out the problem if you can't. Heck if you're near me I'd be happy to meet you and figure out the issue. I've setup and diagnosed issues on a fair share of boats.

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Well isn't my first problem the fact that my anti cavitation plate is an inch or so below my boat? I see I can raise my motor 1 more hole and that would take my anti cavitation plate level to or just above the boat bottom.

Would that make that much of a difference? I'm gonna do it either way but could that be the issue?

What about the prop? Looks like I have the same prop that comes stock with the motor by looking at my specs.

Moose-Hunter, that picture with the green Rebel is my exact set up, but you can't tell if it's the 1650-V, there's like 4 different Rebels.

So first thing I'm doing is raising the motor. What about the tilt since I have to do it manually? I have 5 different holes I can set the tilt at, it's set in the middle now. Should I drop it down closer to the boat?

Not like I can be switching it as I increase my speed, where it's set is where it stays until I stop and lift the motor, pull the pin, put it in a different hole, and drop the motor back down.

Oh yeah and Moose-Hunter, once a job has once begun, never leave it 'til it's done.

grin

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I've always seen the best performace out of the second trim hole.

Just guessing but it sounds to me like a weight distribution issue combined with possibly too much tilt in the motor.

I haven't seen a description of how the boat is acting. It is guess work without knowing the symptoms that go alone with the slow speed.

Is it going slow and plowing water with the bow low?

Is the bow coming up but not plaining?

Is it plaining without getting much speed?

Does it sound like the prop is slipping?

We need more info. If you "think" the trim tabs will work then that sounds like a function of weight distribution and motor trim hole.

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The OP is complaining about top end speed, but doesnt actually know what it is so its completely possible that its within the capabilities of the boat/motor.

Then finds trim tabs as a cure? Um, those will get you on PLANE faster, but will destroy your top end. They are helpful if there is a big disparity in weight distribution as others have mentioned. If all the weight is in the back and the bow rides really high, they would be beneficial for you, BUT they will not help top speed.

So, unless you know engine RPM, actual top speed dont do anything.

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If you're really only getting 10 to 12 mph.... my opinion is you either have a spun prop (slipped hub) or totally too much prop to where you can't reach proper rpm.

Be nice if you had access to a tach. You're under powered but you should do better than that.

again....JMO and repeating what's already been said.

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  • 'we have more fun' FishingMN Creators

No where in your posts do you mention the attitude of the boat.

Is it running with the bow up.

If so re-distribute weight into the bow.

Lower the pin to its lowest position.

Running with the bow plowing.

Move some weight out of the bow.

Raise the pin.

Knowing the RPMs at WOT along with speed at WOT would be helpful BUT those numbers are meaningless it the bow is plowing or high. The boat should be at a proper attitude to use those numbers.

After doing that and finding the boat performing to your satisfaction.

Raising the outboard will decrease drag. Your boat is flat at the transom. While it will pound in the waves that flat transom will help an underpowered boat get on plane.

Your problem could be from a few things.

At setup the outboard is mounted resting on top the transom.

That isn't always the proper height.

Loosen the motor clamps and place a 1x2 between top of transom and outboard to raise the motor height. If you have bolts remove, raise the outboard, seal and replace bolts.

Now experiment with tilt and weight distribution.

Once you get the boat to run at the right attitude you can use the RPM at WOT numbers for prop selection.

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Not exactly the same boat but I have 2000 16-Ft Lund Rebel Tiller with a 25HP Yamaha 4-stroke and I can get 23MPH on flat water. Iam guessing you have a power prop on that motor or the trim is not set correctly.

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Have you tried painting flames on the side of your boat?

I'm about to! After all I finally hit 12mph tonight! LOL

When I first got my GPS going my top speed was 8.5, since then I've raised the motor, tried every tilt location, got new gas, put in new plugs.

It only changes a mile or two per hour or so depending how I load things, not like if I put some heavier stuff up front I go from 8.5mph to 20 mph.

I think it some kind of carb issue or something now, I'm finding out I can go faster at 3/4 throttle then I can at full. Now it's jerking a little more like it wants to go but then doesn't, then it will snap out of it and go a little faster then bog down a bit again.

If I go from idle to full throttle it will just die, starts perfect everytime, idles perfect everytime, goes smooth and nice like normal until about half throttle, not much different from half to 3/4, after 3/4 I actually go slower.

I had carb issues in this motor a few years ago and it was kind of like this, I was told my jets are super tiny and easily clog.

Guess I could just cruise around half throttle and pretend I have a 5hp.

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So this was a test? Engine wasn't running right all along but after five pages of posts this juicy tidbit is finally revealed?

LOL...well, anyway, yeah, you could do that. But, running with clogged jets does, I believe, have potential to damage the engine due to lean mixture.

Never know when might get surprised but I can't imagine the carb is too complex. Sounds like it's time to roll up your sleeves...

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So this was a test? Engine wasn't running right all along but after five pages of posts this juicy tidbit is finally revealed?

LOL...well, anyway, yeah, you could do that. But, running with clogged jets does, I believe, have potential to damage the engine due to lean mixture.

Never know when might get surprised but I can't imagine the carb is too complex. Sounds like it's time to roll up your sleeves...

Well actually the motor was running fine when I started this thread like I said on page 2, after taking it out a few times it has started to spit and sputter toward full throttle. It's always been slow since the day I bought it.

You sound like everyone else that has said that about my carbs until you take a look at them. Carbs are easy, that's no problem, then they pop the hood and tell me to take it to a dealer lol.

I think raising the motor helped alot but now I need to get the motor running smooth again to see the results. I gained about 4 mph doing that even though my motor wasn't running as good as it did the time before I had it on the water.

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I took my Merc to a shop for carb work even though access doesn't look too bad and I have the official Merc Service Manual. Didn't have a good place to do it when it needed to be done. So, yeah, I do understand there are different reasons why people do things differently.

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OK, good news for me, I got the boat going up to 22mph right now with me 190lbs and my 110lb dog. It seems it's the fastest it's ever been since I bought it, although I can't back it up because this is the first time I've actually had gps speed on my boat.

I got the carbs cleaned, new plugs, new gas, raised the motor.

Now after doing research on my motor Honda recommends that the anti-ventilation plate is 0-2 inches BELOW my boat, which is exactly where it was before I messed with it. Right now it's an inch or so ABOVE the boat.

Do you guy's think it's fine right now or would I be better off dropping it back down to where it was? I know sometimes manufactures say things that isn't the best but they say it is.

Seems like I get the best top end speed with the 2nd hole down from the top, but when I turn sharp it makes some porpoising sounds if thats the correct way to put it. The further down I go I lose a mph or so but it seems more stable when I turn.

I'm happy with 22mph it's about what I'd expect, but if someone thinks I can get it to go a few MPH faster with some adjustments I'm all ears.

Thanks for all the replys.

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I'm happy with 22mph it's about what I'd expect, but if someone thinks I can get it to go a few MPH faster with some adjustments I'm all ears.

Thanks for all the replys.

Sounds like you have reached top peed and about all thast is left to gain more speed is to try going down hill with it. grin

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This has been a enjoyable thread. I wonder if I waxed my boat and painted flames on the side how much faster I would go?

grin

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Just a guess here but I'm thinking if I were to wax my boat, paint on the flames, and have the wind at my back I could hit 28mph.

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