Overpowering

hydroforce3 · 14 December 2017, 19:30

hi guys im wondering what would be the dangers of overpowering a SIB by 5hp?, my sib has a max power rating of 15hp but a friend of a friend has offered a straight swap for my current 10hp honda for a 20hp four stroke honda, the dimensions are near enough identical and weight will only be increased by 4.5kg. are there any serious or dangerous consequences of slightly overpowering an inflatable?

cheers

Dan

GuyC · 14 December 2017, 19:39

...and I thought this was going to be a thread about Maximus' Brut 33

beamishken · 16 December 2017, 10:16

Slightly overpowering a boat isn't realy a problem assuming your conservative with the power and the transom is able to carry the weight. The biggest assumed problem is with insurance, there has been several discussions on here regarding wether insurance is available & valid. Maybe speaking to insurers would be a good idea before you go ahead.
The general opinion was that insurance would be void if you overpowered but I seem to remember a recent thread where several people had obtained cover for slightly overpowered boats.
I did get cover for a 30ft cruiser which was overpowered but that's a slightly different ball game.

jeffstevens763@g · 17 December 2017, 15:46

As Bken says but if it's a good deal I would go for it look into having it de-rated to 15 hp

69cmw · 17 December 2017, 19:29

Take the sticker or plate off that says max HP then just use it [emoji106]

hydroforce3 · 17 December 2017, 20:26

thanks guys for your replies I was a bit worried about the transom being ripped off by the sheer power of the new engine but as you have all said it will all be fine il just slowly ease the throttle on, So I'm getting my new engine tomorrow. CANT WAIT now I need the weather and the swells to settle so I can play.

he said it will need a service as he hasn't got around to it this season,

My service will include,
engine oil and filter
fuel filter
gearbox oil change
impeller and key, O-ring, pump housing gasket
fresh spark plugs
pair of anodes (if worn)

anything else you guys think I should change or take a look at before spring 2018?

As for insurance I haven't told them the max that my boat can handle is 15hp so I'll just change from the 10hp to 20hp and hope for the best lol

il post pics when I get the new engine

cheers guys

GuyC · 17 December 2017, 21:13

It's easy for me to say because it isn't my friend of a friend but I'd be tempted to try and get the service done prior to doing the swap. Whilst I'm sure it's OK, the service may highlight any significant issues it may have.

hydroforce3 · 17 December 2017, 21:17

yeah, good point! il get in touch with him and arrange a service, don't want to swap a cracker for a complete dud! did that with a car once and won't be happening again lol, cheers mate

beamishken · 17 December 2017, 22:55

4 stroke engines that have stood are prone to carb issues so a pre swap service is a good idea

rossymtb · 17 December 2017, 23:01

Hydroforce3

Straight swop for a larger engine hp sounds a good deal. Are engines similar age?

I went to alot more hassle to increase mine from 9.8 to 15hp
Ended up buying another complete boat &engine package.

Maybe if he's a friend of yours will allow you to try his engine out first? Or have you already had a go of it.

lightning · 21 December 2017, 19:22

My Zodiac 285s is rated to 8hp max with a recommended 6hp max.

I did have a 6hp on it but upgraded to a 9.8hp Tohatsu which weighed the same as the 6hp.

The boat performs really well with the 9.8, planing without delay, and will achieve close to 20mph with two of us on board.

Also look at the maximum recommendation for transom weight. Ours is rated up to 39kg so well within limits as the Tohatsu weighs 26kg.

The maximum hull speed rating for our Zodiac 285s boat is 17mph and above this speed it is harder to steer. So with a 20hp on a boat rated to a 15hp you might go outside the rated maximum speed of the hull, care would be needed in this case.

hydroforce3 · 24 December 2017, 15:53

Hi guys i have the engine and its immaculate he serviced the engine for me we ended up going halfers on the parts and all it needed was oil and filter change and a set of plugs, gear oil was still blue so brand new and no leaks or water in there, all ive done is grease everything and cleaned out the tell tale pipe with air just so i know nothing can block the water jet hole. I didnt think of hull speed...can this cause unstable keel steer?

Thanks guys

Dan