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Old 11 September 2016, 12:38   #11
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Re-ran compression, 110-115 on too 4 cylinders, bottom right 70, couldn't get to bottom left (port) due to the gauge fitting g fouling the casing. Gonna strip the head off Tuesday see if there's damage to the cylinder or piston I think. At least too 4 seem good!!
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Old 14 September 2016, 06:59   #12
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Head removed, found one difference between top cylinders and bottom 2, small lip/ridge on the bottom (6 O'CLock) of the cylinder right at the top (last 5mm). I assume this is the limit of the piston ring.

Some play across the pistons, but it's uniform across them all so i assume this is normal.

Unsure where to go next, thinking of replacing the O-rings and seeing if that makes a difference, failing that i'm guessing rings or cylinder is warped? (will need a bore gauge)

Incidentally most of the small waterways appear to be blocked with salt and calcium build up.

Only other noticeable difference was a large build up of oil in the two bottom cylinders in the ports (exhaust i think, ports closest to centre of engine).

Anyone know much about changing the rings on these, rings appear about 20, but unsure how many more consumables i need to change in the process (bearings/shims etc)?

Tom
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Old 14 September 2016, 07:19   #13
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I would be inclined to get run a few cans of seafoam or similar through the engine to try and de-carbon. It could be you have a ring sticking. Put the heads back on and give then engines a few hours of use before going to the extent of stripping them. The bores look OK to me, as long as they are smooth I would avoid any more cost.
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Old 14 September 2016, 07:38   #14
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Will do, I've run 2 cans through and it kicked plenty of sludge out, gonna have to wait until i'm on the water to do it again, neighbours weren't happy! Added it direct to the cylinders before will put the last can through with some fuel i guess. Called Mike at southcoast to see if he's got some o-rings. They were pretty stiff. Parts have broken away when i've taken the head off.
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Old 14 September 2016, 15:59   #15
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ona side note anyone know where i can get one of these fuses?

AGA-20 | Cartridge Fuse, F, 20A | Cooper Bussmann

AGA-20amp,

its the small one near the starter, 20amp 32v, i cant find them bloody anywhere! Googling has told me they're called AGA-20.
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Old 25 September 2016, 17:23   #16
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Quick update as progress has been made incase anyone else has similar problems, cleaned all the pistons and head up, and replaced the O-rings. Compression was this the same 115 top 4, and 60 - 65 on the bottom right. (still cant get into bottom left until i buy a new gauge). I suspected a fault with the ignition system from what i'd read on other sites, so renewed the HT leads and plugs, and found many sites suggesting power pack issues so installed a new CDi Power Pack unit.

Took the boat out today, consistently hit 5200 - 5400 rpm with a top speeds at WOT of 42 knots which i'm pretty pleased with.

Plugs looks good after the run and the cylinders that are low are still fetching plenty of oil through. Looks like i'll need to look at re boring to resolve the compression issue, but overall the performance of the engine is back on par with no stalling issues and the miss has also disappeared.
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Old 17 October 2016, 09:30   #17
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Help Please! Can anyone recommend
a) a decent machine shop preferably someone who have experience with outboard engines i guess?
b) where i can go/look to source parts (google only seems to return a sea of US sites)? I know i can get genuine pistons and rings from various suppliers at ridiculous costs but are there any aftermarket parts that are cheaper? Lastly the 3 companies i've spoken to so far didnt know where i'd be able to source a new sleeve or aftermarket pistons.

I'm in Sheffield so the closer the better!

Doing the rebuild myself, so only need someone to measure the damage and carry out the machine work.

Cheers
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Old 17 October 2016, 09:36   #18
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Btw, engine is running really well bar the fuel economy, but the low compression on two cylinders isnt giving me the confidence I want on longer trips.

Racked up around 200miles last week at Linnhe
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Old 17 October 2016, 10:24   #19
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http://www.riversidepowerboats.co.uk/

Try Steve hutch
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Old 18 October 2016, 05:31   #20
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Does it realy need bored? usualy with a 2 stroke as long as it's not scored or badly worn a good hone & set of rings does the trick
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