Jump to content

Re-engining our boat


ChrisE
 Share

Recommended Posts

My brother and I are thinking of exchanging the current 115 yam plus 10 hp Honda for a pair of 60 yams, largely because it will give us better back up than the Honda and both engines will be used so there should be less danger of the back up quietly going tits up.

 

I have a question, does anybody have any idea on relative fuel consumptions of a pair of 60s vs a 115?

 

Many thanks

 

Chris

Link to comment
Share on other sites

Very roughly it will use about 1/3 more fuel than you are currently for the same speed.

It is unlikely to have quite the same performance as the 115 so your fuel may go up a little further than my estimate as you may find you are pushing it harder.

 

If you can go twin 70's you'll match the performance of the single (possibly beat it) and only use the same sort of amount of fuel as the twin 60's.

 

Tom

Link to comment
Share on other sites

It's an Orkney Orcadian 23.

 

Oh dear, another nice idea down the bog...

 

Maybe just a newer 115 then. The current one guzzles like no tomorrow and doesn't get anywhere near the 22 knot boat max speed, prob 16 on a good day with new antifoul..

 

Chris

Link to comment
Share on other sites

That's stumped me Chris!

I didn't know they did an Orcadian 23. I've sold a couple of 20's, but not seen any bigger Orkney's other than the PH and DA.

 

Hmmmm. It's a big boat for a 115Hp, but the hulls were in that transition between semi displacement and semi planing (assuming it's a similar hull to other Orkneys of the same sort of size).

I would have thought it would scrape 20 knots if set -up and propped correctly. What engine is it, 4s or 2s? How old?

Not sure if a new engine is the answer without knowing more, but even with twins it will use more fuel. That said, it sounds like you are running at WOT most of the time already. You may need to simply work to a slower cruising speed or rather than look at changing the engines.... possibly a different package if you want speed and economy?

Link to comment
Share on other sites

Yep, the 23 wasn't a big seller I believe that they made about 10. A nice boat if a little rolly but built like brick do-dah house.

 

The engine is an early Yam 115 4, probably 10-12 years old.

 

You are probably right about a better bet being to chip the lot in for a better economy/ speed package.

 

Thanks for you help, we'll have another head scratch.

 

Chris

 

 

Link to comment
Share on other sites

Had a quick squizz around the Interweb and saw a couple marked for sale.

One on the east coast and two or three dotted around Europe, oddly (for Orkney) right down in the Eastern Med.

 

It all depends on your need for speed.

Fit some hydraulic (or electric) tabs and run at 12 to 14 knots and you'll find you will almost half your fuel consumption for the four or five knots off what you are getting right now.

 

It's what some would describe as a "Fast Fisher", but it really depends on whose definition of fast.

 

Tom

Link to comment
Share on other sites

Oh don't start me on trim tabs!

 

The geometry of the 23 is that there is a platform on the stern where the o/bs are fitted. This preclude the fitting of the pair of Vovlo QLs that I had bought especially for the purpose.....

 

Might go back and have a think about just what is possible tho'

 

Chris

Link to comment
Share on other sites

If the 23 is anything like the 20 then it naturally runs quite bow high and is rather light at the bow.

 

Tabs would, of course, work to help drop the nose and create a more efficient planning surface, but not much use if you can't fit them.

An alternative would be a couple of bags of builders sand up in the forward lockers OR increase the amount of chain used.

This will also give a very much enhanced ride in a head sea, albeit the ride may well be much wetter.

 

There is one very obvious downside to this. That being that when you turn the boat around into the same sea, but now it is following, you would rather have the bow up otherwise you "raise" the risk of a possible broach (boat slewing round as it hits the bottom of a wave trough).

 

It's a toughy, but I do know many Hardy and Orkney owners who sware by a bag or two of sand up in the bow.

 

Try it and see if it has a positive effect on handling and efficiency, but be wary of the possible downside too.

 

Tom

Link to comment
Share on other sites

It's not all about speed Chris.

I'd love Quest II to be faster, but her hull shape means that she'd develop all sorts of odd characteristics if pushed faster and, IMO, she's an awesome sea boat just the way she is.

Quest II cruises around at 12 to 16 knots (I run at about 13) and will scrape 20. It's simply a case of training yourself that that speed is plenty.

 

Your Orcadian is fairly similar, she's happiest at a certain speed and whilst you can enhance the ride and tweek the efficiency, if you really want more speed you need to look at a different boat. But then with a speedier boat, you'll have a whole different set of issues to deal with.

 

Try the sand bag route and let us know how the boat handles, but as you are clearly aware, test it gently with the sea in all directions.

 

All the best

 

Tom

 

 

Link to comment
Share on other sites

 

You will find you will get more torque from a new genearation 2stroke - ETEC & Mariner Opti do a 115 and I am always amazed how BIG the props on them are. Charlie A has an Optimax 75 on his heavy Shetland and it goes some!!! (I even manage some air when he let me have a go! ohmy.gif )

Link to comment
Share on other sites

My work colleague has an Orkney 23 old style Pilot House and gets 20 - 23 knots or so out of it but cruising around at 16/17 knots is best

He has a Honda 130 on the back at the moment but is just getting ( I can picture Tom now ... ) an ETEC 115 smile.gif

Link to comment
Share on other sites

Thank you all for your input. We've decided to hang on to the existing engine (and our cash!) for the minute and have a longer term think about what kind of craft we might replace Hilda Maud with in the future.

 

Hmm, so that means that there will be a few bob left for new tackle, a man can never have enough gear.....

 

Chris

Link to comment
Share on other sites

Hey, Guys

 

What you want is an old 4hp Merc 2s like mine. I only have to refuel every 12 months, but then "Yamabuki Blue" is only 12.5ft. Flat bottom and now has Trim Tabs. Home made of course. laugh.giflaugh.giflaugh.gif

 

Seriously thou guys. Enjoy your boats whatever the size!

 

Alan

Link to comment
Share on other sites

My work colleague has an Orkney 23 old style Pilot House and gets 20 - 23 knots or so out of it but cruising around at 16/17 knots is best

He has a Honda 130 on the back at the moment but is just getting ( I can picture Tom now ... ) an ETEC 115 smile.gif

Ah E-Tec ! wink.gif

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...