40hp or 50hp???

Tim M · 09 February 2004, 20:22

I have a 4.1m Southern Pacific "Cormorant" RIB. The recommended engine for this boat is 40hp. I was wondering whether I might be able to out a 50hp on it without something terrible happening. The transform is pretty beefy - similar to those on RIBs capable of taking much bigger engines. The next model up, the 4.8m can take a 50hp. I was thinking that the transform on that is probably the same construction as on mine.
Anyone got any thoughts on this?

Diesel · 09 February 2004, 20:26

What you really want to be looking for is the maximum weight it can take, You could put a 40hp four stroke on it and it might knacker your transom. So the first thing to do is look at the weight before you look at how big an engine it can have.

Manos · 09 February 2004, 20:28

Concure with Diesel, engine weight is more importantnt than BHP. Although engine power also has some relevance to transom strength.
Best check with manufacturer.

Tim M · 09 February 2004, 20:29

How does one find this out?
Since funds are slim, what ever I get will be a 2-stroke. How much lighter are they?
Surely the manufactures allows quite a bit of leeway for safety when it comes to these matters?

Ian · 09 February 2004, 22:27

is there a manufacturers plate on the transom indicating max. weight and other details?

Phil Davies · 09 February 2004, 22:36

Quote:

Originally posted by timofengland
what ever I get will be a 2-stroke. How much lighter are they?

Call me an anorak if you wish (and Ian and MeMe probably will) but here are some comparative weights of the latest 2-stroke/4-stroke offerings from the major manufacturers. With the modern engines weight differentials between 4 and 2 stroke are significantly less of an issue than they were some years ago. For example the Honda 50 4-stroke weighs 10kgs less than a Yammie 50 2-stroke!:

Mariner 40hp 2cylinder 2-stroke - 75kgs
" 40 and 50hp 3 cyl. 2-stroke - 93kgs
Mariner 40hp 4-stroke 3-cyl. - 93kgs
" 40hp EFI 4-stroke - 98kgs
" 50hp EFI 4-stroke - 112kgs

Suzuki 40/50hp EFI 4-stroke - 110kgs

Honda 40/50hp 4-stroke - 92kgs

Evinrude E-Tec 40/50/60hp direct injection 2-stroke - 107kgs

Yamaha 40hp 2-stroke - 88kgs
" 50hp 2-stroke - 102kgs
" 40hp 3 cyl. 4-stroke - 90kgs
" 40/50hp 4 cyl. 4-stroke - 108kgs

Above weights relate to long shaft engines with power trim/tilt where applicable.

Ian · 09 February 2004, 22:38

Quote:

Originally posted by Phil Davies
Call me an anorak if you wish (and Ian and MeMe probably will

PD, I would never say anything of the sort.

Phil Davies · 09 February 2004, 22:41

Predictably predictable

Red Fox · 09 February 2004, 22:43

There is a chap who has a 4.5 Cormorant and has a 60hp Big Foot 2 stroke on the back (110kg). He has not been out in it yet (I don't think) but might have a view. Come in 'xr770a' where are you?

He bought it here:
www.devamarine.co.uk/southern_pacific.htm
You could give them a ring.

Bill S · 10 February 2004, 08:06

If the makers plate says max 40hp, and you stick a 50hp on, you might find insurance a bit more difficult to source. 'Course if you aint bothered about insurance, then you can put whatever you like on the back. Your call........

Phil Davies · 10 February 2004, 12:20

Quote:

Originally posted by Bill S
If the makers plate says max 40hp, and you stick a 50hp on, you might find insurance a bit more difficult to source.

Has anyone told Suzuki 416, who currently runs a 70hp on his 4m RIB, and who at the London Boat Show told me, with a faintly insane glint in his eye, that if he thought the transom could take the weight he'd lash a 90 on it!!!!?

Suzuki416 · 10 February 2004, 15:20

er,

thanks Phil - I think!

I used to belong to the school of you will NEVER have enough power! Your'll just use it in other ways!

Pete
Always wanted to do 100kts!

Bill S · 10 February 2004, 15:22

More to the point - has he told his insurers?

I've got no beef with anyone who wants to go quicker - the easiest solution is always more horses - but the problem remains - if you exceed the manufacturers plated HP, then insurance will be more difficult (and expensive) to find.
Of course this depends on what you tell them......

Tim M · 10 February 2004, 16:03

The plate on the transform just says 40hp - no mention of a max weight. I've emailed Southern Pacific, will see what they say.

xr770a · 28 February 2004, 14:41

Sorry for the delay Red Fox, yes, I have a 4.5 cormorant with a 60 Big Foot Merc, not been out yet, but Devamarine said no probs at all with the Bigger lump, which weighs a lot less than a 50hp 4 stroke knitting machine. As for insurance no problem, done via Devamarine, excellent shop, staff and products.
.....estimated speed according to Mercury should be around 50 mph, should be fun.
Just finished waxing the lot again today, glad its indoors, just now having a blizzard !