How to get more out of a 15hp 2 stroke yamaha?

[sleepy9]

Hi All

This is my first post here I am looking to buy a 15hp 2 stroke yamaha. Is there any way to increase 2-3hp on that motor? Reason been the boat I am looking to buy require the tohatsu 18hp minimum.
The 5 kg diference between the two motor might not sound much but there is a fair bit of diference between 36kg and 41kg especially and the end of a big day out.

Thanks

 

[robert graham]

Re: How to get more out of a 15hp 2 stroke yamaha?

Not many options regarding hot-rodding modern outboard motors. Maybe search around some more for an 18HP 2 stroke?

 

[99yam40]

Re: How to get more out of a 15hp 2 stroke yamaha?

Hi All

This is my first post here I am looking to buy a 15hp 2 stroke yamaha. Is there any way to increase 2-3hp on that motor? Reason been the boat I am looking to buy require the tohatsu 18hp minimum.
The 5 kg diference between the two motor might not sound much but there is a fair bit of diference between 36kg and 41kg especially and the end of a big day out.

Thanks

What kind of boat has a minimum HP rating?
All I have seen have maximum ratings.
You can up grade a 9.9 to a 15, but never heard of upping it more than that. You can change props or have them modified to a smaller pitch,you just run slower but get more push.
I take it you are not in the US and I believe Yamaha still puts out and sells 20hp 2 strokes outside of the US of A

 

[Silvertip]

Re: How to get more out of a 15hp 2 stroke yamaha?

If a boat requires an 18 HP MINIMUM then the boat is already underpowered. Acceptable boat performance generally is with an engine that is 70 - 75% of the boats maximum rated HP. If that boat calls for 40 HP maximum, then a 28 - 30 HP would provide acceptable performance and with anything less performance becomes marginal, especially if heavily loaded. If you are on the water all day you want more power, not less. What boat size and type are you considering and what is it's MAXIMUM rated HP?

 

[rosscopeeko]

Re: How to get more out of a 15hp 2 stroke yamaha?

I have a yamaha 15hp 2 stroke. It is an excellent motor. I have overloaded my boat and run this little motor on long lake camping trips. It does ok at this, but it is not great. Sometimes it works to plane my boat, which is a wide heavy 12ft aluminum, only when it's heavily loaded. When it's unloaded with 2 people in it, it flies. I too would look for a yamaha 20hp or a 25hp 2 stroke. I have a 25hp 2 stroke that i wanted to hop up, but there isn't a lot of help out there. One guy mentioned milling the head, getting boyesen reeds, and porting to give you a little more power. In the end, this is money, but it might be worth it. Take a look on youtube. I just saw a video of a suzuki 25hp 2 stroke that absolutely rips. This guy has his modded a bit with the mods i just mentioned. Good luck and i would stay yamaha if you can.

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

Thanks to all for the input so far.

I am from Australia.

The minimum 18hp was told by the boat dealer that I want to buy the inflatable from. Its a 3.8m and I will have 3-5 people plus fishing gear.

Like I said a big difference when you try to load and unload this to the back of a sedan between 36-41kg with one person.

 

[connemaraisland]

Re: How to get more out of a 15hp 2 stroke yamaha?

It is a false economy and you will never be happy, buy the maximum rated engine for the boat(rib) and be happy. If you buy a smaller motor and have to trade it it will cost you much more than buying the correct motor in the first place.

 

[99yam40]

Re: How to get more out of a 15hp 2 stroke yamaha?

Thanks to all for the input so far.

I am from Australia.

The minimum 18hp was told by the boat dealer that I want to buy the inflatable from. Its a 3.8m and I will have 3-5 people plus fishing gear.

Like I said a big difference when you try to load and unload this to the back of a sedan between 36-41kg with one person.

If you will be running with 3 to 5 people then you will have help loading and unloading.

Best to get a boat with trailer then you have nothing to worry about

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

If you will be running with 3 to 5 people then you will have help loading and unloading.

Best to get a boat with trailer then you have nothing to worry about

No problem unloading it and packing it at the lake and beaches but I won't have anyone to help at home because all my mates that go fishing with me live around the otherside of the town.

If I have storage room for a trailer I would not be posting these posts.

 

[ENSIGN]

Re: How to get more out of a 15hp 2 stroke yamaha?

I would keep looking for at least a 20hp you can always throttle it down

 

[Silvertip]

Re: How to get more out of a 15hp 2 stroke yamaha?

3 to 5 people plus gear in a 12.5 foot boat?????? Unless this is a vey deep and wide boat I would consider it unsafe with anything more than two folks aboard -- but that depends to a degree on where you boat.

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

3 to 5 people plus gear in a 12.5 foot boat?????? Unless this is a vey deep and wide boat I would consider it unsafe with anything more than two folks aboard -- but that depends to a degree on where you boat.

Its rated to 7 adult. So 5 people with moderate gear is not too much loading. We are not that big in size 60-80kg and yes its one of those honda rebadge v hull inflatable.

 

[99yam40]

Re: How to get more out of a 15hp 2 stroke yamaha?

You never said what the max HP is for it, but I really do not think you will be happy with the way this boat will move with that 15hp motor with all that many people in it.

Have you thought about renting storage to put a trailered boat set up?

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

You never said what the max HP is for it, but I really do not think you will be happy with the way this boat will move with that 15hp motor with all that many people in it.

Have you thought about renting storage to put a trailered boat set up?

It max hp is 30.
Renting storage is out of the question. My bank(wife) dosen't approve it.
My final solution would be buying/making a outboard carrier mount on the tow ball. That way I don't have to lift it all the way into the boot which allow me to buy a 20hp outboard.
Anyone know where I can buy a outboard carrier online?

 

[Silvertip]

Re: How to get more out of a 15hp 2 stroke yamaha?

I mean no disrespect but would you post either a link to your boat or show us a picture. I'd like to see what a 12.5 foot boat looks like that's rated for 7 people. You did say is was 3.8M so to us northern hemisphere folks where toilet water swirls the other way, that figures out to be 3.28 ft/m x 3.8m = 12.46 feet.

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

I mean no disrespect but would you post either a link to your boat or show us a picture. I'd like to see what a 12.5 foot boat looks like that's rated for 7 people. You did say is was 3.8M so to us northern hemisphere folks where toilet water swirls the other way, that figures out to be 3.28 ft/m x 3.8m = 12.46 feet.

No offence taken. My boating experience so far only involve a 2.7m inflatable with a 55lb trolling motor.
Below is the link I am looking at sirocco air hull 3.8m.
http://www.siroccomarine.com.au/sirocco/specifications
Was told it will comfortably serve 4 people and upto 5 people as a fishing boat by the dealer.
And I just check the spec the max hp is 25 hp.

 

[Outsider]

Re: How to get more out of a 15hp 2 stroke yamaha?

.. as a fishing boat by the dealer.

I suspect what the dealer told you is that 18hp would be the minimum you'd want to put on it, as opposed to a requirement. Sounds awfully crowded for fishing, but that's just me. I'd tell the mates you can go fishing when they get everything on the boat, and they can go home when everything is put away, but again, that's just me ...

 

[sleepy9]

Re: How to get more out of a 15hp 2 stroke yamaha?

.. as a fishing boat by the dealer.

I suspect what the dealer told you is that 18hp would be the minimum you'd want to put on it, as opposed to a requirement. Sounds awfully crowded for fishing, but that's just me. I'd tell the mates you can go fishing when they get everything on the boat, and they can go home when everything is put away, but again, that's just me ...

Well the dealer said the boat will definately not going to plane with 5 people on a yahama 15hp. With the tohatsu 18hp is questionable depending on the size of the passengers.

It is pretty crowed for 5 people as a fishing boat but again it will be a rare occassion to have 5 people on board fishing. It will serve 3-4 people most of the time which is ok size.

 

[Silvertip]

Re: How to get more out of a 15hp 2 stroke yamaha?

Being a RIB satisfies my curiosity. Would have been nice to know this up front. According to the web site it will take a 25 HP engine so a 15 would definitely struggle with the loads you indicate.