25 or 30 HP?

simonafloat · 24 October 2015, 11:09

Hi all

Searching around to buy a 25 or 30 HP 2 stroke for my sib this winter. Would I be right in saying that most 25s and 30s have the same block and are therefore similar in weight? If that's the case I may as well get a 30. My aerotec 420 is rated for up to 30hp.

Cheers

Simon

Poly · 24 October 2015, 11:19

Quote:

Originally Posted by simonafloat

Hi all

Searching around to buy a 25 or 30 HP 2 stroke for my sib this winter. Would I be right in saying that most 25s and 30s have the same block and are therefore similar in weight? If that's the case I may as well get a 30. My aerotec 420 is rated for up to 30hp.

Cheers

Simon

Not sure about with four strokes, but my 20hp two stroke is the same block as the 25hp (and the 30hp has an extra cylinder so is not the same!)

spartacus · 24 October 2015, 11:25

25hp Mariner here for under a grand. http://www.willsmarine.co.uk/store-p...rd-engine-£995

As Poly has mention, different weights based on increase from 2-3 cylinder, certainly for Yammies. 2 Stroke Mid Power marine-outboard Products | Yamaha Motor Australia

dave3235 · 24 October 2015, 11:35

Hi

Mariner does a 30hp twin which is the same weight as a 20hp,I think the difference is possibly carb and exhaust change.

dave3235 · 24 October 2015, 11:50

Hi

Here's one on Ebay item no.111798343261.carb clean or electric probs.

simonafloat · 24 October 2015, 16:06

Quote:

Originally Posted by dave3235

Hi

Here's one on Ebay item no.111798343261.carb clean or electric probs.

That does look nice! Need a long shaft ideally but if the right engine came up I would alter the transom

jeffstevens763@g · 24 October 2015, 17:57

Yam 25 @ 54kg two stroke
Yam 30 @ 59 kg through to 66kg according to an Australian site
As a comparison Suzuki 25 @ 62kg 30 @ 71kg four stroke 2015 models
I went for the maximum engine size on mine less work on the engine OMO

Landlockedpirate · 24 October 2015, 18:17

As mentioned above, largely depends on the number of cylinders.

For instance, Yamaha did make a 2 cyl block that was 20/25/30 hp, and were all a similar weight. They also make a 3 cyl thats 30/40/50 hp and those are a lot heavier.

Roflhat · 25 October 2015, 10:28

Quote:

Originally Posted by Landlockedpirate

As mentioned above, largely depends on the number of cylinders.

For instance, Yamaha did make a 2 cyl block that was 20/25/30 hp, and were all a similar weight. They also make a 3 cyl thats 30/40/50 hp and those are a lot heavier.

The 2 stroke 40hp and 50hp 3cyl are the same block, the 30hp 3cyl is different. The 2 cylinder tohatsu 25 and 30 are the same, just a restriction behind the carb I think

Landlockedpirate · 25 October 2015, 10:53

Quote:

Originally Posted by Roflhat

The 2 stroke 40hp and 50hp 3cyl are the same block, the 30hp 3cyl is different.

The OP's question was about weight,I know they are not exactly the same.

Was making the point that you can get Yam 30's that are similar in weight to a 20, but you can also get Yam 30's that are similar in weight to a 50.

Trust me, you dont want to try picking up a 3 Cyl 30 and sticking it on the back of your SIB.

C-NUMB · 25 October 2015, 16:08

Tohatsu 2strokes 25hp and 30hp has the same weight(basically same engine), the long shaft was out of memory abt 52 kg. I had a 25 on my aerotec 420 and that was sufficient but no harm done to have little extra hp.

Roflhat · 25 October 2015, 21:20

Quote:

Originally Posted by Landlockedpirate

The OP's question was about weight,I know they are not exactly the same.

Was making the point that you can get Yam 30's that are similar in weight to a 20, but you can also get Yam 30's that are similar in weight to a 50.

Trust me, you dont want to try picking up a 3 Cyl 30 and sticking it on the back of your SIB.

Sorry, misunderstood! Yes you are right the 2cyl is considerably lighter than the 3cyl

sunsport · 26 October 2015, 12:29

i have had a 20 yamaha on a aertoec 380 for 4 years plenty off power for normal use will pull waterskiers up to 13 stone have just recently fitted yam 30 3 cyl model this is not auto lube and is connected to steering and remotes not much weight difference but would advise remotes on the larger engine as it would be easy to flip with your weight and a heavy engine on the transom ,have been close a few times. superb performance with the 30 proper powerboat . but if i was not using the boat for skiing i would still be using the twenty ,either way do no not forget your kill cord as with both engines it is a superb power to weight ratio and you will get lots off smiles per mile ,happy boating

simonafloat · 26 October 2015, 18:38

Thanks all!

I currently use a mariner 15 2 stroke on the boat and tbh its perfect 90% of the time. I believe it's just 34kg and is very easy to carry around. But if we are 4 up plus picnic tent etc we could do with a bit more va va voom. 1 up with a tiller controlled 30 HP would be interesting.

sunsport · 26 October 2015, 19:18

the 380 does not accelerate onto the plane ,it launches itself ,my wife has skied behind it for years ,but the 30 tears the handle out of her hands unless you feather the power on.top end isnt much quicker but it gets there in half the time , dont let anyone put you off just be aware that the boat is at the upper limits on being safe, your only live once so enjoy.cheers

piotr · 27 October 2015, 12:15

I recently bought a mint 2003 Tohatsu 25hp two-stroke. It's a down-tuned 30hp. Can be easily converted to 30hp. Weighs 51kg.

9D280 · 28 October 2015, 10:16

Ok, a wee bit late here with my 2P's worth, but there is (as you have seen) no sweeping answer.....

Also for a given manufacture the "shared block" may change with model year.... E.G. the Johnsorude 25 sometime in the mid 70s went from being the same basic lump as the 20 to then being a de- tuned 30 (35?) and also got this new fangled thru' prop exhaust thing at the same time - and of course the new 25 Hp head wouldnlt fit the old leg....

The best thing to do is pull the specs for the engine you are looking at, then compare the CC & weight of the bgger / smaller lumps.

OTher thing to check is how easy a change is it? I upped a Suzy DT25 to a 30Hp by changing a throttle cam and a WOT stop on the middle carb! I have read threads in here about new exhausts , and even new ECUs (spark advance & the like type changes), so If you are serious about an upgrade do some reasearch or you may end up being cheaper just buying the bigger HP variant!

Boatinfo.no has a lot of useful reference material (and I think is run by someone on here?)