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Old 19 December 2011, 08:47   #41
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Old 19 December 2011, 08:51   #42
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You really need to sort the sensors out first before messing with props. There's an oil level sensor and an oil flow sensor which both need the wiring connecting properly otherwise the engine won't rev out. Some models also have a reset button on the port side of casing.

I'd also run on a oil/petrol mix until I was sure the lube system is working properly. The oil flow sensor filter is notorious for clogging up but can be dismantled and cleaned. Oil pump will need bleeding after doing this. (8mm bolt on top of oil pump)
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Old 19 December 2011, 08:58   #43
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Quote:
Originally Posted by DM View Post
You really need to sort the sensors out first before messing with props. There's an oil level sensor and an oil flow sensor which both need the wiring connecting properly otherwise the engine won't rev out. Some models also have a reset button on the port side of casing.

I'd also run on a oil/petrol mix until I was sure the lube system is working properly. The oil flow sensor filter is notorious for clogging up but can be dismantled and cleaned. Oil pump will need bleeding after doing this. (8mm bolt on top of oil pump)
as its hitting 5,000rpm I was thinking that the sensors might be OK? I was hoping that it would top out at 4,000 which from what I can find may indicate a limp home mode kind off thing. Seems nice and smokey at the minute so I think its gettign oil OK but you are quite right I should strip it to be sure.
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Old 19 December 2011, 09:31   #44
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On the calcs presented earlier in the thread, your RPM and GPS speed appear to be consistent with a 12" pitch prop.
What surprises me is that you can only make 5000 rpm with that set-up. This could be down to the motor being down on compression, so wise to do the checks you're proposing and a carb clean-up/balance/tune wouldn't be a bad idea if the compression is ok.
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Old 19 December 2011, 16:45   #45
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90 on the top cylinder and 120 on the bottom 2, not ideal but not the end of the world? Please tell me it OK....
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Old 19 December 2011, 16:51   #46
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sorry mate, that is a sign things are not well in there, they will only get worse if left unattended :-(

was the motor warm when you done that?

if the motor was cold there is a chance you have a stuck ring (unlikely but possible)

if you have an outboard shop nearby they will have a scope to have a peak in the chamber, if not buy a USB one on ebay and have a look yourself. OR you could of course take the head off and have a looksy.

i would hazard a guess you will find either scoring or a crack :-(

i sincerely hope i'm wrong though.

cheers
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Old 19 December 2011, 17:29   #47
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bum :-(

I have a usb camera in work (I knew it would come in handy!). Will have a peek and see whats going on. Engine was coldish - ran for 2 or 3 mins before testing.

Least bad scenario is a stuck ring, any ideas on how easy it is to pull a piston out of a DT55? Fully aware of the lottery of buying a used outboard so maybe this dice roll was not landing in my favour...
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Old 19 December 2011, 17:47   #48
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sorry buddy, how to get it out that particular engine is not my strong suit but i assume it is not the end of the world-this is assuming you don't snap a bolt which i would guess is likely to happen if your not careful i.e heat or wd40 as applicable and let it do its job.

if you scope it and you find a crack i wouldn't waste a spanner on it. if you find scoring you could get oversize pistons and a rebore but you will end up with a fairly large bill. good thing is you know you will end up with a rebuilt motor for less than chancing a 2nd hand one again.

let us know how you go but your wise to look at this now before it gets worse and i wouldn't do nothing until you look at why that cylinder is low.

if it is a stuck ring it should be easy enough to sort compared to the other options.

EDIT- there is one other possibility and that is the gasket has gone on the top cylinder so a few cheap options it could be.

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Old 08 January 2012, 15:03   #49
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bores look OK so I took it out again and it went well for about 30 mins, making full rpm but max speed was 25 knots so too small for the boat.

It then went into the limp home mode again so I am convinced it is an electrical fault with the sensors. But as its not fast enough for me anyway I am going put something bigger on it and sell it as is if I can.

Spoke the a local outboard chap who used to be the Suzukin dealer and the pressure drops he reckoned were OK for that engine and he has seen many work fine like that (given the age of them). So could be an easy fix but like I say cant be bothered any more so have taken the decision to replace!

Thanks to all for their tips. Will report back on how it goes with a 75HP!
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Old 08 January 2012, 15:15   #50
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please tell us your local dealer so we can avoid them for outboard sales if they think that difference is "OK".

good luck with your new 75 when you get it.

cheers
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