Veideo of my Lencraft 4.8m and DT55 on the water - Page 3

TomKat · 19 December 2011, 13:47

DM · 19 December 2011, 13:51

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)

TomKat · 19 December 2011, 13:58

Quote:

Originally Posted by DM

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.

Downhilldai · 19 December 2011, 14:31

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.

TomKat · 19 December 2011, 21:45

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....

Xk59D · 19 December 2011, 21:51

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

TomKat · 19 December 2011, 22:29

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...

Xk59D · 19 December 2011, 22:47

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.

cheers

TomKat · 08 January 2012, 20:03

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!

Xk59D · 08 January 2012, 20:15

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

TomKat · 08 January 2012, 20:42

I think their point was that for an engine that is almost 30 years old a pressure drop is not the end of the world as long as it runs OK but I could be putting words into their mouths!

Xk59D · 08 January 2012, 21:09

30psi is close to the end of the world in outboard terms :-).

there is something amiss in that top cylinder obviously.

i'd rather have 3 cylinders the same at 90psi than the readings you got.

running ok is relative, i think your not running ok which is a result of the PSI reading. your probably losing a good 3/4knots and 500rpm with that reading.

will the engine work for someone pottering about-yes without doubt. however it still doesn't change the fact the motor needs pulled apart if the owner cared. it is only a matter of time before whatever it is becomes terminal and it will no doubt be in the middle of nowhere it happens and not going back on the trailer.

btw i have had an engine before like that, funnily enough a suzuki 85 the same model as yours. after winterisation i had lost about 5/6knots, upon inspection with compression tester the top cylinder was about 35 psi off. took the head off and seen a crack-i.e the end of the world! :-(.

enjoy your new motor-take the compression gauge with you when buying and trust me, not your outboard dealer, if the PSI is 5 or so of a diff then walk away :-)

cheers