Compression etc on a coupla old Evinrudes

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    Posted: 13 Feb 2017 at 10:17am
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I'm after opinions and suggestions on these motors... anything could be helpful besides "Buy a new motor" because I absolutely categorically do not have the money for that :p

First off I've got a 135hp 1974 Evinrude with cylinder compressions at:
122
122
99
118
Opinions: Good/bad/tollerable, maintenance etc I could do to possibly improve the low one? I've done some research and got sime.ideas but there's some extremely knowledge fullas among you lot.

Other issue I'm having with the 135 is it idles badly. Give it any throttle at all and it runs smoothly for as long as you want it to but try and sit still... nope. Have done spark plugs, running a brand new battery, checked carb and jets are clean etc.

Secondly my flatmate has a 1986 Australian built 40hp Evinrude. This one is a lot sadder running at 109 and 50 psi. It goes but not happily.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 2017 at 1:28pm
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1st tried to find outboard engine compression specs on the net.. or even in manuals?
Sry good luck...even service repair manuals dont give compression specs in most cases.
What the do say is all compressions should be close together 5 or 10% from memory

Other issue I'm having with the 135 is it idles badly. Give it any throttle at all and it runs smoothly for as long as you want it to but try and sit still... nope.
 Keep in mind this is pre unleaded fuel.. even so a seal or crap in the idle ciruit of the carbs...but more commonalty the idle advance....If compressions.. these are idle compressions  are a little down then the advance needs 1 or 2 degs to fire the fuel reliably..
Rule of thumb higher the cylinder pressure (Not compression ratio) the less advance, faster flame across the chamber.
 in saying that .. that 99lb is a little low.

Bottom line thu.. there are no short cuts, they will come back and bite you in the bum, and pocket.
The only way to really tell is strip down , check bores etc then decide where to go from there

If one watches around, and may take a yr or so.. took me just over 2 yrs....till a good engine at a fair price pops up on trademe...

 What boat is the engine on the back of and what is the boat used for?
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Post Options Post Options   Likes (0) Likes(0)   Quote Kevin.S Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 2017 at 1:50pm
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This is from an Evinrude repair manual -which I have in pdf if you need a copy.


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Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2017 at 10:07am
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Originally posted by NZR NZR wrote:

I'm after opinions and suggestions on these motors... anything could be helpful besides "Buy a new motor" because I absolutely categorically do not have the money for that :p

First off I've got a 135hp 1974 Evinrude with cylinder compressions at:
122
122
99
118
Opinions: Good/bad/tollerable, maintenance etc I could do to possibly improve the low one? I've done some research and got sime.ideas but there's some extremely knowledge fullas among you lot.

Other issue I'm having with the 135 is it idles badly. Give it any throttle at all and it runs smoothly for as long as you want it to but try and sit still... nope. Have done spark plugs, running a brand new battery, checked carb and jets are clean etc.

Secondly my flatmate has a 1986 Australian built 40hp Evinrude. This one is a lot sadder running at 109 and 50 psi. It goes but not happily.
Kevins manual sounds really useful info.
Re Evinrude 40hp you should be able to get spares if needed with a bit of googling etc.  My 40 - I stripped it down using manual which I bought (don't have now) - removed leg got stripped power head checked by a shop and water pump serviced and checked, reassembled and it ran sweet - he put s/h pistons in as damaged - the water pump impellars are not very robust compared to later designs so it may have overheated at some point.  With a manual you can do it yourself - biggest problem is frozen bolts from corrosion being difficult to remove - heat works wonders on these.
You can easily remove a side plate that lets you look into exhaust port fairly easily - these can rot out letting water into bores as well, then you can look at piston and bores - you will probably find 50psi pot badly scored.  You need to fix that as it will be terminal fairly soon if not now.
Good fishing trip nothing breaks, great trip catch fish.
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Post Options Post Options   Likes (0) Likes(0)   Quote Durban Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2017 at 11:49pm
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Two things will cause the drop in the compression worn or damaged sleeve and carbon ed rings that are stuck in the ring grooves .You can find out if the rings are not moving freely in the ring groves by removing the covers on the block 2 on the port side and 2 starboard side this will give you aces to the rings viewing them through the reed valve ports . To view them through the exhaust ports you need to remove the exhaust port bubble back situated between the 2 cylinder heads , I recommend to remove this cover because then you also have aces to the exhaust port area as these old motors have a corrosion problem being used in salt water the water from the impeller comes up between the 2 cylinder heads in the channel[ the cover to the channel is situated just below the flywheel at the aft end ] and corrode resulting with a hole and the water then ends up in the ports and end up getting into the block
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Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2017 at 5:14am
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or it could jst be a head gasket......simple things first......

What cylinder is @ 99psi?, assume its #3 given your order but some people count cylinders left/right and some up/down
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Post Options Post Options   Likes (0) Likes(0)   Quote NZR Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2017 at 10:20am
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Thanks everyone. Got some investigating to do this weekend :D

Originally posted by Grasshoppa Grasshoppa wrote:

or it could jst be a head gasket......simple things first......

What cylinder is @ 99psi?, assume its #3 given your order but some people count cylinders left/right and some up/down



As follows:
1: 122
2: 122
3: 118
4: 99
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Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2017 at 10:31am
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i would bet my left .....  the bottom crank seal has failed or maybe the lower exhaust has rotted out as described by Durban, both let water into bottom cylinder which rusts/seizes rings
Does the sparkplug from #4 appear rusty or discoloured compared to the other 3?

Unfortunately neither of these issues are economic to repair, if water has been present the crankshaft will be shot

Depending on where in Wellington you are i'm happy to have a quick look over things for you
Will PM with some contact details
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Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2017 at 4:16pm
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Originally posted by Grasshoppa Grasshoppa wrote:

i would bet my left .....  the bottom crank seal has failed or maybe the lower exhaust has rotted out as described by Durban, both let water into bottom cylinder which rusts/seizes rings
Does the sparkplug from #4 appear rusty or discoloured compared to the other 3?

Unfortunately neither of these issues are economic to repair, if water has been present the crankshaft will be shot

 
A story re repair and pull it down rather than she will be ok - I had a Mercury 115 2S 17ft boat that brother (we co owned boat) took over to barrier towing behind a bigger boat - motor not running being towed - he lost it on way when tow rope broke in rough seas and recovered 2 days later floating with bow only visible -he was told to strip down and recondition but didn't want to - another shop (yes he shopped around) said flush it and you will be fine.... any way he flushed motor with fresh water and then CRC in bores and ran it within a few days - it went for 2 months afterwards - developed a rattle then threw a rod - we pulled it down and rust throughout and crank shaft not pretty, big ends all gone.  Got another power head from a motor that had hit a rock and smashed  gearbox/leg and all go. 
Good fishing trip nothing breaks, great trip catch fish.
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Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2017 at 7:40am
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So how'd things go NZR? Occasionally "knowledge fullas" are interested in outcomes......helps qualify any advice,opinions etc and a common courtesy 
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