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Discussion Starter · #1 ·
I have a 3.95 tinnie, aluminum. has forward controls and is in need of a new outboard.
Its an old stile and is very heavy, deep v with high sides. The out board was stuffed when I got it and was a 20hp johnson. I have been using a 9.9 merk. tiller steer but it struggles to get on the plain with two of us in.
So here's the problem, do I go the 15hp at $2200 or do I get a 30hp merk for $2900.
There is a big difference in physical size, there is 9kg difference in weight also.
I have spoken to two dealers who both say the 15hp will be plenty but I am unsure.
Any comments would be a help from those who have tinnies.

Shane.
 

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depends on what you use it for, anything more than yourself in it and the 15 will struggle and will probably need a smaller prop to perform at all loaded. I have a 15hp longshaft yamaha on a 375 Quintrex Dart and whilst it goes ok Id love to put a 20 on it and remove the restrictor plate in the carby to get 25hp. On a deep V 395 the smallest Id go is a 25hp 2stroke never ever look at 4 stroke.

Go the 30, they are actually a big 2 cylinder tohatsu, much better down low and will give great performance unloaded or good performance loaded.

Id ignore what the dealers have said, unless they are an old bloke or have skin like a ****** they have no ****ing idea what they are talking about.

I personally go a Yamaha 30hp 2 stroke for smoothness and lack of noise but thats me. Then you can pluck the restrictor and swap the carby jets for 40hp :) :) Dont worry about the warranty, its a 2 stroke.
 

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Definitely go the 30hp, Too much horsepower is better than not enough especially with boats
I reckon the 15 will struggle once you have a couple of blokes with gear etc
 

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Discussion Starter · #4 ·
The dealer also said that if I go the 30hp it will keep skipping from side to side when on the plain. is that right?

cheers
 

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Nope, its a deep V 4m tinny.

He is talking about chine walking which is when the keel of the boat is actually out of the water and therefore does not track in a straight line and is all over the shop. Normal cure is to raise the motor until the keel is back in the water.

Dealer sounds farkin hopeless.

Are you fitting it yourself or having the dealer fit?
 

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The dealer also said that if I go the 30hp it will keep skipping from side to side when on the plain. is that right?

cheers
Afraid I must disagree with Benno here. That boat is only 13ft in the old currency and 30hp will be a handful unless it's got a big load in it. Don't Merc make a 20hp anymore, as I reckon that would be ideal. I'm talking from experience here as I used to be an outboard mechanic, and overpowered tinnies have given me a few frights!
 

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KICKEN BACK IN THE BUSH
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30 HP ,check with the manufacturer (should have a plate on the hull with max engine size) i bet its to big for the boat
My first wee tiny was a 13 foot with a 25 HP,and fug what a weapon and what a hand full
Every time we nailed it ,it nearly flipped,
Even lifted my mate sitting over the bow clean outta the water
Never sat on the plane (no matter what we did)
 

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Get a tohatsu 18 nice and light and plenty of grunt. If a 9.9 gets it on the plane in normal use then the 18 will eat it
 

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Afraid I must disagree with Benno here. That boat is only 13ft in the old currency and 30hp will be a handful unless it's got a big load in it. Don't Merc make a 20hp anymore, as I reckon that would be ideal. I'm talking from experience here as I used to be an outboard mechanic, and overpowered tinnies have given me a few frights!
Merc dont make a 20hp, you have japanese (tohatsu) to 15hp, a single USA made 15hp shift in tiller 15hp, then tohatsu 25s to about 60hp.
 

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Discussion Starter · #11 ·
The merc 20,25,30hp are all the same physical size, the 9.9 and the 15 are the same physical size. I will check out the 18 tohatsu, My way of thinking was that if you are only paying $500 more for twice the size why not. but at the same time if its not safe then no, I would not.
I'll go out and see if I can see something about max size motor.


cheers
 

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The merc 20,25,30hp are all the same physical size, the 9.9 and the 15 are the same physical size. I will check out the 18 tohatsu, My way of thinking was that if you are only paying $500 more for twice the size why not. but at the same time if its not safe then no, I would not.
I'll go out and see if I can see something about max size motor.


cheers
no such thing as a new Merc 20 mate

Mercury Marine

Mercury Marine
 

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Im running a 15 hp mariner on a savage snipe 3.8m, and it hammers.

I had a 20hp johnson, and nearly flipped the boat.

Note, my boat is a little bit smaller and lighter then yours
 

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Discussion Starter · #14 ·
Yes you are right benno, but the dealer has a late model second hand one on display. Thats how I know they are the same size.
Just had a look for a plate with the make on it but nothing, nothing on rego papers either, so back to square one.


cheers.
 

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It takes next to no time to convert a Tohatsu 25 to a 30. Very well known mod and you will actually have a part left over. A smaller motor then the 25, the Tohatsu 9.9, 15 and 18 are also basically the same motor, but I don't know if the lower hp ones can be "converted" to the 18 easily.
 

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I have a 3.95 tinnie, aluminum. has forward controls and is in need of a new outboard.
Its an old stile and is very heavy, deep v with high sides. The out board was stuffed when I got it and was a 20hp johnson. I have been using a 9.9 merk. tiller steer but it struggles to get on the plain with two of us in.
So here's the problem, do I go the 15hp at $2200 or do I get a 30hp merk for $2900.
There is a big difference in physical size, there is 9kg difference in weight also.
I have spoken to two dealers who both say the 15hp will be plenty but I am unsure.
Any comments would be a help from those who have tinnies.

Shane.
mate I had the same size boat early last year had the same problem
I ended up going for the 30 (long shaft, they have electric start, its worth it)
then I sold it 12 months ago for less then I paid for the motor alone
 

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Go the 30hp. I've been in both and the difference is huge. You won't regret spending the extra cash.
 

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Yup go the 30hp. Have a 25hp on the 4.2 dory and with three people on board she's a struggler to reach max rpm. Of course the dory isn't a deep V hull either which will suck some more power. Does it have a compliance plate? It will list maximum everything. Maximum HP on a 4.2 dory is 40hp!
 

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go the maximum that its rated for
 
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