Question about a 17ft dory.

[alandav123]

Hi all, I recently had fitted a 90HP 4 stroke Mariner to my dory hulled boat. It is sitting a bit low at the back and even novice people walking round the harbour comment on it.
This is probably partly due to the added outboard weight and any accumulated water will no be running to the back end adding to the problem.
I am fully aware that the outboard is too big and way too powerful for this boat but thats another story.
Given that the boat is in the water, is it feesible to ballast the front end with say 100 or 150 kilos. as there is a cubby there for storage. I have heard some say I could get some hessian bags filled with small smooth stones that will nestle down to a nice evenly distibuted load.
I know that I am kind of changing the boats payload etc but I am trying to make the best of the situation I am in.

Any constructive suggestions would be gratefully recieved.
Regards Alan in Arbroath

 

[Channel Ribs]

I like chain as ballast, it is easy(ish) to move and comes in handy in it's own right.

Still, you could part exchange the engine for a 40.

 

[Nautical]

Hi Alan

Unfortunately it is not just a matter of re-ballasting the boat. If the motor is over rated for the size of boat all sorts of problems can arise not least insurance, have a smash up into the side of a nice £1/2m sports cruiser and watch your insurance company sink you faster than the bling you holed!.

Other issue will be that your boat has a certain rated payload add the extra weight of that size of motor and the extra ballast required for'd and you probably have'nt much stability left with a few bods on board which is fine if the water is like a mirror all the time but in lumpy stuff it will handle all jittery and horrible and more than likely go tits up.

Sorry to be a bit of a downer and not that constructive but reality unfortunately.

 

[duncan]

it all depends on the boat to - my Dell Quay Malibu was 17'6" and came with a 90 Merc as standard and they fitted 135s for barefoot skiing..............equally a 17ft Boston Whaler will handle a 90 fine too.

 

[Stoaty]

I wouldn't panic too much. there are loads of 17ft dorys with that size outboard on them. I have even seen them with 150hp on. It will look low at the back but once your on board and your mate and the anchor and sandwiches are in the cuddy it will be fine.

Look here and here

You'll find more if you browse that site.

 

[jfm]

Agreed. 90hp should be fine on a 17foot dory. The pic below shows one with a merc 125hp and -in the picture of it in the water- a 5hp aux. It's same hull mould as the second link in Stoaty's post above, the Nab 17 (but better boat than the Nab) and doesn't sit low at the back.

It makes sense to stow the fuel forward-ish eg in the centre console, not at the stern

Exactly which dory is it that is struggling with the Mariner 90? Picture?

 

[thefatlady]

Some 25 years ago, I had a 100hp straight-6 Mercury on a 17 ft dory. Probably a heavier engine, given it's age (about 1968 vintage). No problem. It also had a 10hp Suzuki spare. This is it.

 

[scej]

from Memory the dory was rated to 115 Hp the version that the Royal Marines use is rated to 140. However these where rated when 4 stroke was not around so i would check the weight of your 4 stroke against the comparable 90 two stroke and see what the weight difference is. for instance Yamaha 115 4 St is the same weight as their 200 2st so you should be able to work out why it sits low at the stern just from that.

I friend of mine had a 17 cuddy with a 140 on it and it was fine apart from being a bit lively in teh chop and at the time we worked for the company based in Poole who wher building the Dory boats

 

[Chris_d]

Just another thought, some dories if not all dories? are double skinned and the void between hull and inner moulding filled with foam. This is where the Boston Whaler types get their unsinkable tag from, however older dories have a habit of leaking and the void fills with water, this will obviously all run down towards the engine, that plus any rainwater in the cockpit. Could explain your excessive list at the stern.