70hp Johnson, lost compression on one cylinder...

Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Topic: 70hp Johnson, lost compression on one cylinder...
    Posted: 30 Jul 2017 at 3:21pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
G'day guys, we had the old Fi-Glass Dominator out in the sun today and after running awesome for half an hour or so the engine (93, Johnson 70hp 2 stroke) stuttered and died. It would restart but wouldn't idle so in the hope of not making things worse we lowered the aux and managed to get back to the ramp. It runs on premix 50:1 and I always mix my own 20L tote tanks and did this today with fresh fuel.

Back home I compression tested the old girl and the top cylinder compression is only 30psi. The others are still 125. I guess it's now a question of is it worthwhile rebuilding an old engine like this or should we just reopen the boat now and accept the loss?

Would appreciate what you guys think?
TIA
Macca
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Elevate Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 4:22pm
Elevate View Drop Down
Silver
Silver


Joined: 11 Sep 2010
Location: West Auckland
Status: Offline
Points: 102
Ah bugger :/ We were in a simalar situation with a slightly older 50hp johnson.

For us it wasnt worth buying a brand new engine for the old boat it was on.

Looked at buying a second hand engine, but with that we didnt know the history and who knows how long it would last.

We waited a bit to see if any used freshly rebuilt ones came up but nothing suitable came up at the time so went with rebuilding the engine we had. as it was in pretty good condition for its age and everything else on it was in really good condition.

Least we know it was all done and the workshop who did it knew the engine inside out now haha.

I guess it depends on how long you plan to keep the boat? and what the budget can stretch to.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 4:48pm
Grasshoppa View Drop Down
Gold
Gold
Avatar

Joined: 17 Sep 2007
Location: Wellington
Status: Offline
Points: 555
Really depends on what damage etc suffered internally, could be as simple as blown head gasket.....or as bad as damaged pistion/bore etc, suffice to say it'll take a mechanic to advise from here
Rest of motor will want to be in pretty good condition to warrant rebuilding at that age is my thoughts
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 5:30pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Cheers Jaspa - yeah mate, we are gutted as we saved long and hard for this boat. Its not much to look at, but get a lot of enjoyment out of it and is only worth 8-9K when it was going. Have just spent most of winter rewiring her and fitting new bimini's and instruments....Unfortunately we will struggle to repower the boat as there are other priorities which require the dollars. We are pretty much resigned to leaving her in the shed for a while now and scouring TM to see if another Johnson 70HP of similar vintage pops up. At least this way we will have a parts engine as well! Wink
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 5:33pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Cheers Grasshoppa, yeah mate, I hear ya... I know in my heart thats its not going to be worth rebuilding - no doubt they will find other things wrong and then it becomes an issue of throwing more money at an already tired engine. Would be great to pick up another Johnson 70HP of similar age so we could do a straight swap, a quick look at TM this arvo shows a newer outboard like a Yamaha  is probably going to run 4-5K, which is over half the value of the entire boat. Cry
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote DIY Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 5:49pm
DIY View Drop Down
Gold
Gold


Joined: 20 Apr 2012
Status: Offline
Points: 626
How about getting a workshop manual and giving it a go yourself. Sounds like you might have nothing to loose. At least strip it down and see if you can find the issues. I'm sure a lot of people on here would give advise if you can post up pictures etc. I have bought parts from Boats.net in the States and shipped with Youshop they work out quite cheap. Just a thought.
Oh what a smasher - two eggs and a rasher!
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 6:00pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Gday DIY, yep, I have the workshop manual.... next weekend Im going to pop the head off and have a nosy at the damage inside...will definitely post pics. Issue now is having confidence in the engine once or if, it is repaired... like you say, nothing to lose at this point tho. Appreciate the advice mate.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote DIY Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2017 at 6:43pm
DIY View Drop Down
Gold
Gold


Joined: 20 Apr 2012
Status: Offline
Points: 626
Nice one, good on you for giving it a go. I've got a Tohatsu 2 stroke and do all the servicing myself. Going through the manual everything looks doable. Just think it might get tricky setting up the carbs. Hopefully you might not need to touch those.
Oh what a smasher - two eggs and a rasher!
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2017 at 1:17pm
MacSkipper View Drop Down
Titanium
Titanium
Avatar

Joined: 04 Jul 2014
Location: Manukau Harbour
Status: Offline
Points: 4478
I rebuilt a 75 Johnson 40hp - had manual - stripped down to power head and for peace of mind got a marine mechanic to strip and check power head and gearbox, then I reassembled (painting and tidying wiring etc) - he gapped and checked points removed flywheel as part of powerhead inspection - if I had tools and experience could have done whole lot myself - at his suggestion bought back assembled and test run in his workshop - started first pop and ran perfectly afterwards except plugs would foul after a few hrs running (start missing particularly when cold/idle) needed hotter plugs.  Good motors but water pump impellers pretty fragile best to change annually and check pump flow at first start of day (should anyway) and parts hard to get in NZ now as not many around.
Good fishing trip nothing breaks, great trip catch fish.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2017 at 3:56pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Gday lads, I got the head off this afternoon as I couldn't stop thinking about what damage was hidden inside.... the top cylinder which lost compression has minor scoring you can see and feel with a finger nail in the cylinder wall. The other two cylinders still feel smooth as glass.

There is no sign of a cracked or overheated head or blown gasket or any other dodgy noises. Surprisingly, the water passages were pretty clean with little corrosion or deposits. So, perhaps its just a piston ring that has gone in that top cylinder... I could have a go myself, but if the costs of this type of repair are reasonable, I guess it may be better for someone more experienced than me to do it. The cylinder wall is definitely going to need machining as well I would assume.

Any thoughts on this guys? Costs or advice? Appreciate all the help so far...
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2017 at 6:09pm
MacSkipper View Drop Down
Titanium
Titanium
Avatar

Joined: 04 Jul 2014
Location: Manukau Harbour
Status: Offline
Points: 4478
Not sure who does this in Wellington - I wonder if a piston rang has cracked?  What does spark plug look like compared to other pots?  If rusty then water present from cooling galleries....
Good fishing trip nothing breaks, great trip catch fish.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2017 at 6:50pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Plugs all look pretty good. No rust or any signs of water in the block. Water cooling galleries all look clear with very little sediment or corrosion. Head gasket looked good, no evidence of any blowby. Im going to get in touch with Scott at Coastal Outboards and see what he reckons... at this point, I think its worth having it disassembled and inspected by a pro, then if its beyond economic repair at least we will know.
Back to Top
Post Options Post Options   Likes (1) Likes(1)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2017 at 6:54am
MacSkipper View Drop Down
Titanium
Titanium
Avatar

Joined: 04 Jul 2014
Location: Manukau Harbour
Status: Offline
Points: 4478
Originally posted by NZMacca NZMacca wrote:

Plugs all look pretty good. No rust or any signs of water in the block. Water cooling galleries all look clear with very little sediment or corrosion. Head gasket looked good, no evidence of any blowby. Im going to get in touch with Scott at Coastal Outboards and see what he reckons... at this point, I think its worth having it disassembled and inspected by a pro, then if its beyond economic repair at least we will know.
if you can find an agreeable mechanic (make it clear what you expect and that you are realistic) getting him to work on power head only and you do rest will save you dollars.  Suggest when reassembled take in for first start as he would be able to tell you if something drastically wrong which may save you further damage or a row home?  I did this and he tweaked idle etc and gave it thumbs up - no hassles! 
As a carrot (to mechanic) say you will be looking at a repower at some point in future and will remember the service you received at that time - and please do.
Good fishing trip nothing breaks, great trip catch fish.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2017 at 8:34am
Grasshoppa View Drop Down
Gold
Gold
Avatar

Joined: 17 Sep 2007
Location: Wellington
Status: Offline
Points: 555
Where in Wellington do you keep boat?
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2017 at 8:59am
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
Gday Grasshopper, we keep it in our garage on a trailer in Upper Hutt.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Elevate Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2017 at 6:16pm
Elevate View Drop Down
Silver
Silver


Joined: 11 Sep 2010
Location: West Auckland
Status: Offline
Points: 102
heres a link to a crowd in the states, has parts schematics and part numbers etc if you need to order anything, they have alot of older stuff available.

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1993&hp=70
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote NZMacca Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 2017 at 11:02pm
NZMacca View Drop Down
Bronze
Bronze


Joined: 07 Feb 2017
Location: Wellington
Status: Offline
Points: 14
G'day lads, well thought I would finish off the thread with the final outcome. After much consideration and looking at other second hand motors (that had unknown history and cost more than our rebuild) we had the motor assessed and repaired by Scott at Coastal Outboards. Top quality bloke and excellent workmanship.

The fault was a severely scored no1 cylinder and piston, most likely caused by a cracked piston ring. The engine was fully dismantled, inspected and then fully rebuilt with new parts where needed. The engine is now back on the boat and we hope to get a few more years out of her yet. Interestingly, we were using Valvoline Outboard oil... Scott reckoned he had seen a lot of motors with our symptoms, all running on this type of oil. Coincidence or not, we changed to some OEM oil while we run the newly rebuilt engine in and will then look at the options.

Thanks for all the help and advice lads, hope this thread helps someone in the future.

Cheers
Macca
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote kishidabu Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jun 2018 at 4:33pm
kishidabu View Drop Down
Bronze
Bronze


Joined: 09 May 2017
Status: Offline
Points: 6
I have the same issue with my '82 60hp Johnson.  Can I ask what it cost to get it fixed?
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote kishidabu Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jun 2018 at 4:35pm
kishidabu View Drop Down
Bronze
Bronze


Joined: 09 May 2017
Status: Offline
Points: 6
BTW I use valvoline as well
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote kinger Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jun 2018 at 6:54pm
kinger View Drop Down
Silver
Silver
Avatar

Joined: 15 Nov 2009
Location: Taupo
Status: Offline
Points: 137
Just an FYI.
I had a 1973 50 which lost a bit of ring and scored the bore.
Because of the age, it took a lot of ebay to source the oversize rings, but after getting the barrel bored, and despite much nay saying, I stripped and rebuilt myself for a grand total of less then two hundred bucks.
Runs like a dream, starts first pop, and both compressions sit nicely over 140.
Give it a go. All you can do is **** a ****ed engine.
Back to Top
Forum Jump
Forum Permissions View Drop Down


This page was generated in 0.391 seconds.

Fishing Reports Visit Reports

Saltwater Fishing Reports
Top of the South Fishing Report - 22/03/24

Tasman and Golden Bay snapper still running hot We are not far away from daylight... Read More >

22 Mar 2024
Saltwater Fishing Reports
Bay of Islands Fishing Report - 22/03/24

Variety is the spice of life On one recent trip, the plan was to spend a... Read More >

22 Mar 2024
Saltwater Fishing Reports
Hauraki Gulf Fishing Report - 22/03/24

Fish where the fish are! Catching fish or just going fishing? I tackle this issue... Read More >

22 Mar 2024
Saltwater Fishing Reports
Inner Hauraki Gulf Fishing Report - 22/03/24

Thoughtful tactics required for better fish Over the course of each year the fishing varies,... Read More >

22 Mar 2024
Fishing bite times Fishing bite times

Major Bites

Minor Bites

Major Bites

Minor Bites