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Current Replies for Replacing Atomic 4 with Yanmar YSB8
  Replacing Atomic 4 with Yanmar YSB8 (malteskipper)
Posted: 1:19:54 pm on 1/22/2015 Modified: Never
Does anybody know if this will be a fairly straightforward replacement?
  Re: Replacing Atomic 4 with Yanmar YSB8 (whippet)
Posted: 8:27:45 pm on 1/22/2015 Modified: Never
From everything i have read, this will be an expensive replacement.  Many systems including all fuel and others will have to be replaced, and decoupling and re-aligning shaft is not simple job.

Is the A4 in need of major overhaul, or are you doing for fear of the gasoline engine?  

There are many discussions of this topic on the Moyer Marine forum, where there are many loyal fans of the A4.   I might also suggest you pose your question there.    You will get an outpouring of advice and opinions.

1981 MkIII, Hull 886
Etobicoke YC, Toronto ON

  Re: Replacing Atomic 4 with Yanmar YSB8 (Van_Isle)
Posted: 11:19:37 pm on 1/22/2015 Modified: Never
Yes and considering the YSB8 was only made in 1976/77 ... it very well could be as old as your A4? As well ... I'm sure 8hp would move the boat fine, but you won't have much reserve there. Even C&C, when they started offering diesel as an option, used the YSB12. Most diesel installations seem to be done with > 14hp.

North Saanich, B.C.

  Re: Replacing Atomic 4 with Yanmar YSB8 (davidww1)
Posted: 5:17:13 pm on 1/23/2015 Modified: Never
I'd be disinclined to install an older engine, unless a) it's one of these never-completed-project engines that has been sitting in someone's basement in its crate for decades and b) it's being offered at pennies on the dollar. The problem with older engines is that they end-of-life engines very quickly these days, so you could be stranded for lack of some simple part. Our club's head mechanic told me about scouring the globe for a delisted part for a Volvo engine 12 years old Yanmar is probably much the same.

The other issue with an engine of this vintage is that the old diesels were not designed for smooth running, just efficiency. I assume this is a single cylinder? If so, the vibration will flip quarters placed on the cockpit sole.

Finally, as Whippet notes, you will have to replace a number of other items in the boat, going from an A4: larger steel L's for the engine bed, better fuel filter; new return line to the tank; new exhaust hose; new anti-siphon valve for same; new water trap muffler; larger diameter stern exhaust fitting; new prop pitched for the engine and while you're at it, you might as well replace the stern gland, cutless bearing and shaft. Oh, and the control panel won't fit the existing opening. Putting all this together isn't terribly hard, but there's a lot to get through.

The mechanic noted above, who did about half the work on my changeover, thought it was pretty straightforward, but I was certainly glad to have him as a resource for the work I did.

Notwithstanding all the above, I'm glad to have a diesel. No, I wasn't afraid of the A4 blowing up but it was a balky, fussy, unreliable PITA and I'm glad to be rid of it.

David Weatherston
Towser, Toronto
C&C 27 Mk IV

  Re: Replacing Atomic 4 with Yanmar YSB8 (bosco)
Posted: 10:28:37 am on 1/24/2015 Modified: Never
I second Steve's thoughts. If your A-4 has lasted this long, it proves these beasts are strong, reliable engines. You can basically reset the odometer/hour meter back to zero by getting a rebuilt A-4 from Moyer for under $5,000. The installation will be a " drop-in" with no extras to buy or worry about. Unless you are very young, the rebuilt will outlast you ( and your boat ).

Clare Jordan.     Aragorn
  Re: Replacing Atomic 4 with Yanmar YSB8 (malteskipper)
Posted: 8:31:18 pm on 1/24/2015 Modified: Never
Thank you all for all the useful answers.
I will follow the advice and give the old Atomic 4 another chance.
Alex Flamengo
  Re: Replacing Atomic 4 with Yanmar YSB8 (Van_Isle)
Posted: 1:09:53 pm on 1/26/2015 Modified: Never
If you do go for a rebuild ... or rebuilt ... take the opportunity while the engine is pulled to replace the fuel tank. I'm not sure if all the 27's were the same but there was no way my original tank was coming out the cockpit lazarette (79 MkIII).

North Saanich, B.C.

  Re: Replacing Atomic 4 with Yanmar YSB8 (Katara)
Posted: 9:25:52 pm on 2/17/2015 Modified: Never
The Moyer engine is $4880.00 plus tax , plus shipping , plus $700.00 core charge (if engine is rebuildable)

Beta Marine has  good diesel replacement for the atomic 4 (beta 14)

I'm sailing on a budget so searched high and low for a good runner used Atomic 4 and ended up getting electronic ignition with the used engine i found for $1400.00 , i also cleaned out the fuel tank (nasty) and installed a in line water separator fuel filter .very pleased and it ran fantastic last season

I also think that the yanmar is underpowered for your application

Gerard Warner
Katara, '79 Mk III
D.Y.C.  Ontario