2 stroke engine choice/weight/cylinders 25/30/40

Max... · 20 May 2016, 07:55

I'm a bit in the dark regarding the larger 2 strokes - specifically 25, 30 and 40 hp.

Considering a new boat and the engine would likely be one of these sizes - can anyone explain the choices out there for say the last 15 years from Yam, Merc, Mariner? Not looking to buy older than this. The 40 would need to be PTT.

Do the 25 and 30 share the same block (weight?) - how many cylinders in each size - what sort of weight? Best specific models to aim for?

Cheers guys.

Poly · 20 May 2016, 08:02

Quote:

Originally Posted by Max...

Do the 25 and 30 share the same block (weight?) - how many cylinders in each size - what sort of weight? Best specific models to aim for?

It depends! Some Yam 20/25 are the same block (2 cyl). Some Yam 25/30 are the same block. No 2str Yam 20 and 30 were the same block!

Fenlander · 20 May 2016, 09:03

Max,

It's not a size I have complete understanding of but in my (paperwork not virtual) folder I have some info from when I looked at hard trailed boats and larger 2-strokes from early/mid 2000s.

Mercury... 25/30 near identical at 430cc 2-cyls 51kg. I think then the jump to 40hp was a 3cyl larger capacity 70kg lump.

Confusingly Mercury also did what's called a Sea Pro/Marathon you sometimes see advertised where the 30/40 are the same... a much more chunky motor at 644cc 2cyl which I think is 70kg+.

Tohatsu with the 25/30 being a 429 2cyl 51kg and the 40 jumping to a 697 3cyl 75kg.

As Poly says Yamaha are odd doing a 25 395 2cyl 50kg and also a 25/30 496 3cyl 60kg.

Thats about all I have noted in the file.

Anyway... what new boat would be OK with 25-40hp range... small RIB? RNLI thingy? Going trailed?

Max... · 20 May 2016, 09:24

Quote:

Originally Posted by Fenlander

Anyway... what new boat would be OK with 25-40hp range... small RIB? RNLI thingy? Going trailed?

Cheers Poly, David.

Ahh, talking two boats not one.

Same old story, Y-Class or SR4 (for the 40).

Remind me again what your 4S 20 Suz' numbers are? - weight, WOT on the BAT, fuel, price...

Fenlander · 20 May 2016, 10:58

Suzuki DF20A... £2300 or thereabouts... 44kg.

Not fully run in remember and only trialled at speed with a fair load and in choppy water for just a few seconds before backing off due to conditions.

Load... persons + dog = 532lbs then add all the kit and 20l fuel.

With a 10" prop it repeatedly climbed to 5750rpm and 19Kts in short sections and the only time I could keep the throttle wide open for 20sec I saw 20.5Kts without the rev limiter cutting in but it was far too rough to take my eye off the sea and look at the revs... I'd guess around 6000-6100rpm.

With your loads I reckon an 11" prop would suit better for another couple of knots.

But for me the impressive thing rather than flat out speed is being able to operate in the up to 19kt range without that lag after opening the throttle waiting for the boat speed to catch up which I've had with 10 & 15hp motors and our normal load.... it's much more instant.

Max... · 20 May 2016, 11:22

Is the 20 the biggest on that block?

Fenlander · 20 May 2016, 11:28

Yes... Jeff has the 25 version on his trailed setup. Extra cylinder, 30% extra capacity, another £550 and weighs 62kg.

HDAV · 20 May 2016, 12:49

Mariner 25 is a 2 pot (same as Yamaha?) the larger are 3 pot so heavier.

Saw some very deft handling of Yamaha 40 tillers (manual trim and tilt) on the beach this week in Portugal by the watersports guys.

Max... · 20 May 2016, 16:47

Cheers.

Anyone got more on the 40's - Yam? Are they mostly 2 cylinder.

What's the advantage with a 3 cyl 40 over the 2 cyl 40? More grunt/holeshot? Less stressed?

jeffstevens763@g · 20 May 2016, 18:43

Max

Go on Ron hale marine site you can compare yam, suzi,merc, tohatsu ,Honda are larger engines than you want it gives all the points gizmos all the weights long short shaft.

Cheers

beerbelly · 20 May 2016, 19:07

my merc 40 on the sr4 is a twin cyl single carb and has plenty of grunt for the little avon I was chatting to an old guy who was dragging his fishing boat in up on the west coast of Scotland and he said my outboard was a quite sought after unit apparently very simple no issues and very reliable

spartacus · 20 May 2016, 20:37

I've owned a mid 80s Yamaha 25D (2 cylinder) and a mid 90s (3 cylinder) engine. Both were manual start and trim, but I can honestly say they were fantastic engines. Service them, and these engines will run and run.

The 25hp is perfect on a SIB. I had it on a Zodiac MK IIC. Plenty grunt and with 2-up was perfectly matched. The short shaft engine weight 48kg. The 40hp was on a Zodiac Pro 7-Man Rib. Again, fine 2-up, but the extra weight of the boat, and it's about on its limit. Weight wise for long shaft, then around 85kg. The 40hp shares the same block as the 50G. The 50hp is nigh impossible to find (favoured by commercial fishing). It also had different carbs and a larger exhaust manifold.

Max... · 20 May 2016, 20:51

Is that used stuff though Jeff from BITD? ie 2000 to 2006 or so?

Fenlander · 20 May 2016, 21:43

Max a site I use is smalloutboards.com in the USA. They are sellers but leave all their historical listings up.

So if for example you Google Yamaha 25hp smalloutboards.com you get this...

25 hp Yamaha Outboard For Sale Tiller

Several images, usually a weight and sometimes capacity/cyl no. and some facts.

Results are a bit random but I've picked up useful data on older motors.

jeffstevens763@g · 21 May 2016, 11:11

Quote:

Originally Posted by Max...

Is that used stuff though Jeff from BITD? ie 2000 to 2006 or so?

Sorry max pitched in mid thread talking 4st but having said that weights not far off 2 st now, Barnet marine were selling 2st should be some info there Plus tohatsu site give 2st specs.

Cheers

jeffstevens763@g · 21 May 2016, 11:15

Quote:

Originally Posted by Fenlander

Max a site I use is smalloutboards.com in the USA. They are sellers but leave all their historical listings up.

So if for example you Google Yamaha 25hp smalloutboards.com you get this...

25 hp Yamaha Outboard For Sale Tiller

Several images, usually a weight and sometimes capacity/cyl no. and some facts.

Results are a bit random but I've picked up useful data on older motors.

That's not much lighter than mine and I paid £2600 new nice engine though.

jeffstevens763@g · 21 May 2016, 11:17

Look at woods of crediton mod stuff last I looked marina 40hp for sale.

Cheers

Max... · 21 May 2016, 13:00

Thanks again all - Spartacus, missed your post very useful.

As some may know from the ever running Y CLass topic I've always fancied one of these and the itch won't go away so I will have to get one eventually. I will look out for a 2 stroke 25 short shaft if anyone knows of a decent one around, preference would be a Merc/Mariner circa 2006 to match my 15, love these engines.

I will keep my 15 but want to try a 25 on the Aerotec and that will give me the choice for different days and have the 25 for the Y when it comes...

Might even go with a crazy idea of using a compact (easily detachable and bolted up through the Y floor) console running the 25 on remotes and transform the Y into a kind of "baby brother to SR4" mini "SRIB"...

http://www.rib.net/forum/f50/central...tml#post263163