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Old 17 September 2023, 14:50   #1
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Johnson 15hp 2-stroke. Post purchase checks & service.

As mentioned in a recent thread I've bought this outboard on something of a whim, part fun/project and part to see how it suits the Aerotec. Furthermore Willk hinted this maintenance thread might follow on and I hate to disappoint.

The outboard is a 2003 Johnson model J15RSTD. Usefully just under 34kg. Bought with eyes open from a guy at the coast who'd owned it a couple of years , only used once last year and then just left it in the shed. Priced to allow for some work. Just looked it and him over, didn't test start.

The pics below are actually after I'd done the cosmetics. Spray the sand abraded skeg and the prop too for the same reason. Also touched in some paint chips with a small brush. Finally a T-cut and polish.

I was lucky with the prop as the wear is just paint loss and it's otherwise 100% true. An 11" unusually for an old 15hp. We'll see how it revs in use soon. Good too the splines had obviously been greased recently in terms of hours run.

I found a manual online at...

http://f4ewz.free.fr/wp-content/uplo...06_215688E.pdf

And for me more interesting, the maintenance manual...

http://files.motorka.org/plm/jo-ev/J...ice.Manual.pdf
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Old 17 September 2023, 15:04   #2
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Before a test run in the bucket I went through all the nuts and fixings for tightness. Oiled all links/pivots and greased where appropriate. Please to see again in hours run terms it had all been greased recently.

The plugs looked almost new and in the photo of them out just a carb cleaned blast bought them up clean so it obviously runs OK. They were the wrong type though, actually for the previous generation of this motor, so I fitted the correct Champion Q type. Apparently something special about the interference suppression compared to a standard resistor plug.

I'd ordered a cheap tach. Hope it works long enough to suss the prop/revs but it's not waterproofed well at all. There's no seal on the battery compartment so I've run a bead of silicone.
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Old 17 September 2023, 15:24   #3
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Felt it was time to test start/run in the bucket. It came with proper Johnson tank and line, as it uses the same 50:1 as my Tohatsu I transferred some of that fuel to the Johnson tank. Looking round realised I'd not bought its kill cord home, temp sorted with a twist of wire. Filled the bucket with water and pumped the primer.... damn fuel sprayed in a fan from the connection at the outboard end. Despite clicking on positively it was wobbly. Couldn't work out why the fuel leak was so dramatic but decided to rig up the hose straight into the OB's fuel pump inlet. This is on a plastic cover that has the filter screen under. Sadly the 20yr old age hardened spigot snapped off while I was trying to force on a too tight hose! Still keen to hear it run I applied even higher levels of bodgerey to get fuel to the carb involving a neighbour holding a plastic taper into the fuel pump. This was impossible to make total free of air leaks. Add to that we found the wire twist temp kill cord substitute was only intermittently doing the job so we had fuel... sometimes... and a spark... sometimes... but not always together.

On the few times it burst into life it was with the typical rorty 2-stroke keenness. But only a dribble from the tell tale. That's a good arrangement in that there's a spigot on the head and it's so easy to remove the short hose that exits the lower cowl to poke/blow out. Once that was done we had a good fire hose spray.

At this point both satisfied and frustrated in equal measure I called it a day. I did check out the fuel leak to find some Johnsons have the same fuel connection to the outboard as the tank, both 8mm. But this model is 8mm at the tank and 6mm at the outboard... and the guy had given me the line from another of his outboards. Once I'd sussed this I bought the correct 6mm connector.

Also ordered and fitted a new fuel pump as the filter cover with spigot is impossible to find in the UK online whereas the pumps are easily sourced.
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Old 17 September 2023, 15:33   #4
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In changing the fuel pump I found a great bit of design re maintenance, the lower cowl is a plastic clamshell and easily comes off with 5 screws. This gives easy access to those bits low down on the powerhead that on most portable 2-strokes of this era are a pig to access.

While in that area I had a look at the tilt mechanism... which didn't tilt at all. I found wear, play and stretch in the linkage was just stopping the hooks freeing from the trim pin to tilt up. Tightening, minimal filing and grease sorted that.
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Old 17 September 2023, 15:41   #5
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Lower unit oil change next. Standard job. The old oil was only a little discoloured, free of water, silt and metal filings which is a result. You never know 'till you look. I get on well just using the tube nozzle to pump up from the drain plug.

I took the intake screens off and it was all free of debris there. Also removed the anodes and cleaned up their backs and the surface they contact.

I was happy to see the paint chipped away on the thermostat housing bolts as it's the best place to look in and get some idea of the waterway condition... and good to know someone has bothered. Just light "dust" and no deposits of any significance. I tested the stat opening/closing in a saucepan of water and that was fine.

Always compression test a new to me engine... 105psi both cylinders. For a cold/dry reading on a 2-stroke pulled over by hand that's fine.
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Old 17 September 2023, 15:47   #6
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While I was about the lower unit I carefully loosened all the retaining bolts. They were all at a sensible torque and came out easily as they were greased. Excellent as that's half the battle sorted when I go to do the impeller once we've tested the motor runs OK at sea.

The only other autumn/winter job will be a carb strip and new gasket set.

There's some really good extra info on these motors at LeeRoy's ramblings...

https://www.leeroysramblings.com/Out...0articles.html
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Old 17 September 2023, 16:10   #7
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Nice one David, as I said in the previous - a mighty fine looking OB, just something timeless with the white finish and Johnson logo.

...and knowing you it will be a well running one before long too.
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Old 18 September 2023, 13:42   #8
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Well with new fuel pump, correct fuel line connection and the new kill cord she's a runner. It's my guess this hadn't run for perhaps two years before my aborted attempt the other day. Third pull start this time and quickly settled down to a choke back in even idle. I really like the ability to set a higher idle speed if you want from the twist adjuster on the end of the tiller.

Another good feature is the flush plug on the side of the powerhead... a flush down from top to bottom make sense to me. Removed the stat and gave it a good run through from the flush point with the garden hose once the engine had warmed to loosen any deposits.

Weather is against getting out any day before this Sat so I'll get an impeller and do that in the meantime.
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Old 18 September 2023, 13:57   #9
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Looking good David
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Old 18 September 2023, 17:38   #10
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Thanks Steve.

Decided to pop the lower unit off to check if I just needed an impeller or whole pump kit.

Routine job really but this one was super easy to come apart. As usual left two bolts half in until appropriate tapping with the rubber hammer had started to drop the gear case. On this motor you just get a bit of a gap then the gear change rod clamp screw is seen. It's a better arrangement than some in that it screws to a fixed position, on some makes you have to measure the position of a clamping screw or the gears don't properly engage after assembly.

Nothing untoward seen once the pump assy was apart. It needs an impeller, gaskets and a lower plate so I'll order a kit.

Took the opportunity to flush the engine again from the upper flush port with a good flow seen from the pickup pipe.
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Old 19 September 2023, 09:00   #11
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My son has a 9.9 GT with the restrictor plate removed so technically a 15
On his T38, he gets 18 mph 2 up and 22 solo and this is around Morecambe bay
The acceleration is superb and it's surprisingly very economic on fuel
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Old 19 September 2023, 09:27   #12
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Looking good so far. Nice article . That's a nice looking engine,
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Old 19 September 2023, 18:48   #13
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Thanks guys. Good to hear your comments re performance Tommy.

Not much on today so had a look at the carb. You have to remove the recoil start and air intake box to access but that's easy and only 5 bolts in total.

What was more problematical was that the maker's manual way to access one nut is to remove the plastic link indicated by my screwdriver. This link is on a plastic spigot and retained by an O-ring in an external groove.

Given I like to have the ability to remove the carb at the slip in an emergency on a day out this seemed complicated so I fettled a spare spanner to allow it to fit without removing the linkage and that's going in the toolkit I carry..
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Old 19 September 2023, 19:07   #14
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Quote:
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...and that's going in the toolkit I carry..
Tch!

You had been making such excellent progress and now this - making tools to carry down the slipway...
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Old 19 September 2023, 19:36   #15
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Well think of all the weight ground away as a saving not the spanner as a gain. I have a motorcycle tourer mate nearby who cuts half the handle length off all his tools to save space and weight.

Getting the carb apart I was pleased to see a very clean float bowl and no other issues. Silly small nice detail on this carb... the gaskets being a rubber type which don't stick to flanges and tear like the paper ones.

Slightly different to clean than many in that the main jet is removable from the side of the emulsion tube housing rather than the bottom... and the emulsion tube is non-removable being sealed in by an alloy plug.

Float height and drop measured to spec but they are rarely out unless fiddled with.

Rebuild/gasket set arrives tomorrow so it won't be apart for long.

While I had the recoil off I took the opportunity to make up an emergency pull cord.
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Old 20 September 2023, 07:36   #16
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I have a motorcycle tourer mate nearby who cuts half the handle length off all his tools to save space and weight.
You think that's bad - check out the lightweight hiking crowd. I saw a guy cut off all his clothing/gear labels and weigh them - he saved soooo many grammes...
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Old 20 September 2023, 09:01   #17
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You think that's bad - check out the lightweight hiking crowd. I saw a guy cut off all his clothing/gear labels and weigh them - he saved soooo many grammes...


I recall a bloke taking the piss out of my cheapish not so lightweight pushbike. He had a very expensive, lift it on your little finger jobby. He didnít see the funny side when I pointed out that his outfit would still be much heavier than mine, when he parked his 17st fat arse on the saddle. Iím 12st7lbÖ
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Old 20 September 2023, 09:36   #18
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I was about to make the cycle reference PD. In the mountain bike community folks will spend thousand more than my modest outfit to save every extra 100g... yet wipe that out advantage with a rucksack packed with energy bars and more fluid than they'd drink in a week marooned on one of Donny's islands.

Unfortunately I'll have to find a way to shave a bit more weight from my kit for tool offset... the Johnson needs imperial spanners so I'll need to add those to my otherwise metric toolkit.
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Old 20 September 2023, 09:55   #19
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I was about to make the cycle reference PD. In the mountain bike community folks will spend thousand more than my modest outfit to save every extra 100g... yet wipe that out advantage with a rucksack packed with energy bars and more fluid than they'd drink in a week marooned on one of Donny's islands.

Unfortunately I'll have to find a way to shave a bit more weight from my kit for tool offset... the Johnson needs imperial spanners so I'll need to add those to my otherwise metric toolkit.
You could just keep a can of carb cleaner in the car. A few squirts of that in the air intake usually sorts many carb issues when on a day out
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Old 20 September 2023, 10:16   #20
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Technically incorrect. Anything sprayed in the air intake just goes through the 1" dia (or so) throat of the carb into the engine in a spilt second which is not the place blockages occur. It may help an engine start for a few seconds but will not resolve the problem.

Running issues that appear out of the blue are so often idle or main jet blockages from debris that has sat in the bottom of the float bowl or even varnish/gum build up from older fuel. Only taking off the float bowl, cleaning out and clearing the jets can sort the issue. Nothing sprayed into the intake gets through to these fuel flow paths.
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