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Old 24 August 2021, 10:43   #1
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2 Stroke Outboard Servicing

Hi All,

I’m sure the has been covered numerous times before but I couldn’t find anything obvious when searching topics... I’d put it more down to me getting older and loosing touch with technology.. (I’m only 34 :-s)

I Currently have two 2 Stroke Outboards - A Yamaha 2B and recently managed to pick up this Johnson 4HP Seahorse for £100... I’m sure I got a bargain on the Johnson.

The Johnson appears immaculate given its age and started first time and ran whilst we burnt the fresh fuel down in tank without cutting out..

I want to service my own outboards but I’m the kind of guy that struggles with an IKEA flat pack.. how easy is it to service a 2 stroke outboard are all 2 strokes similar as in will a general guide cover it or would I be looking at two separate guides for Yamaha and the Johnson.

Also the Johnson is a 4BR78E so would appreciate any general feedback on this engine if anyone has any experience of it, haven’t managed to get out on water with it yet due to work and tides being out of sync :-(
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Old 24 August 2021, 13:15   #2
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Both of those are lovely little motors. Well done. The Johnson particularly - nice and smooth twin cylinder motor.

Servicing them is nice and simple too - mostly changing the gear oil, spark plug(s), bit of grease here and there.

I think I might have some service guides for the 2B, I'll have a look.
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Old 24 August 2021, 13:20   #3
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Here you go:
* 2B Owners Manual
* Parts Guide
* Alternate Owners Manual
* Impeller Replacement Guide

password is rib.net
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Old 24 August 2021, 14:09   #4
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Thanks Matt very kind of you to upload them.

Had a quick look through!!

So servicing is well within the average persons capabilities - do you need to do something with carburettor as well?
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Old 24 August 2021, 14:37   #5
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Only if it needs something doing. IMVHO worst thing you can do is dismantle stuff that doesn't need it. So if the motors run fine, I'd leave the carbs alone and only dismantle them if there's a problem.
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Old 24 August 2021, 15:24   #6
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Only thing I will add is make sure you run it dry after use, there's stuff (rubber and fibre washers) in those carbs that won't like being soaked in E10 for long periods
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Old 24 August 2021, 17:20   #7
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Don't forget about the anodes
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Old 24 August 2021, 17:33   #8
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Only thing I'd add, and often gets overlooked, is periodically replace the starter rope. Yes, it's not broken, but when it breaks, then you have a problem. Salt water, oil, petrol and general wear and tear all take their toll. Quicksilver supply the replacement rope.

With the engine running - you can slowly inspect the rope if your draw it out from the cowl. Again, that's just an inspection, personally I'd replace it.

There's is a knack to replacing it - otherwise the spring recoil will retract minus the rope! Hopefully you'll find some how-to videos on YouTube.
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Old 26 August 2021, 13:46   #9
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So took the Johnson 4HP out yesterday despite looking immaculate from the outside it wasn’t particularly smooth...

Started up fine, got about 25 Mins in and it started to run a little rough and appeared to be juddering, looked at the fuel tank and appeared a little low, so topped it up ran it for another 5-10 Mins and the same happened again... this appeared to happen when at full revs..

Decided to head back and cruise along the shore close proximity to avoid getting stranded and it begun to run happy again without issue.. after continually fiddling with fuel tap choke in out shake it all about and continually re adjusting the vent (An amateur equivalent of blowing the dust out of it and hitting it with the yellow pages)

A Couple of things have sprung to mind, the engine is a 50:1 mix I had about 2.5L of 100:1 mix so at the petrol station added another 2.5L assuming this would dilute the mix... still not 50:1 but a lot closer... I didn’t get much smoke from the engine... would the mix cause the outboard to conk out and take multiple attempts to restart..

The other thing I’m thinking is the fuel tap which is a brass tap under the cowling at the back of the tank, should this be fully open or closed or half way.. I’m thinking if I was restricting fuel this would obviously cause problems

Feedback appreciated.
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Old 26 August 2021, 13:56   #10
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50:1 is twice as much oil as 100:1 so if starting with 100:1 and wanting 50:1 you'd need to add oil.

I'd probably mix up some fuel correctly and run the engine in a bucket to see how it is with the right amount of lubrication and take it from there. Hopefully if you were running it with hardly any oil it will be ok.

If still lumpy when revving then the usual suspect is the fuel flow so it tends to be a case of working through that.

I recall you recently got the engine so what maintenance have you done so far? If none then probably worth flushing the tank, replacing the fuel filter and even removing the carb and giving it a good clean. Then check plug, maybe thermostat and the impeller along with gearbox oil etc. Ie a bit of a basic service.
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Old 26 August 2021, 14:26   #11
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Mate thank you for your detailed feedback it’s appreciated, I have to admit I have very very little knowledge of outboards, really is an area I have to at least get a basic understanding.. some of your prompts have given me a cold sweat!! Haha

I brought the outboard of the most charming elderly gentleman he brought it 35 years ago, last used 25 years ago... he told me he changed spark plugs and emptied and cleaned fuel tank prior to my purchase, I also saw it run faultless for 30+ mins whilst it drained the fuel tank - so was assuming I had a good buy it’s immaculate on outside

Ohh the shame, I’ve just re read the Oil/Fuel chart I’ve been reading your quite right re it being more oil, so instead of diluting I should of been adding!!
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Old 26 August 2021, 14:57   #12
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I shouldn't worry. You've either murdered it or not. It had some oil and as you couldn't rev it then you could well be very lucky.

If it hasn't been used for 25 years then it may well not have any wear on it and be a cracking motor but you do need to service it as age just perishes certain things.

None of this is difficult even for someone who has lost a fight with an IKEA chair.

Bin all the fuel for starters. Empty the engine tank and the canister. Lawnmowers will drink it happily enough as will a nearly full car tank.

You need to buy a service pack for that outboard and then set about replacing the impeller, the gearbox oil and fuel filter. I would also buy a can of carb cleaner and remove the carb and give that a good wash as a minimum. Personally, I remove the fuel pump plate and float pot and leave the whole lot submerged in clean fuel overnight.

You don't need anything more than some spanners and screwdrivers and just work slowly and gently through each phase. Always sensible to take pictures as you go along and loads of people on here can help with each step.

Once you've done that then the chances are you'll be off and running with a good motor.

Whether you want to start by draining the fuel and firing it back up with the correct mix (you'd really want to get rid of all the old fuel from the engine and carb first) to check that it isn't fubared is a personal choice.
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Old 26 August 2021, 16:30   #13
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I'm fully with tmorris above but would add, be obsessive about accurately mixing your 2-stoke mix. Buy a proper measure and measure out both your petrol and oil. Most people know too little oil=less lubrication=trouble but too much oil, far from being "good" =lean mixture=overheating=trouble
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Old 26 August 2021, 16:47   #14
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Thank you both, once again I’m appreciative of your responses.

Re the fuel tap any idea if these ones are meant to be fully open? I’ve read something about a reserve when fully turned one way then half way open means tap fully open then the other way closed... does that make sense to anyone... I assumed it would just be fully open for free flow?
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Old 26 August 2021, 20:15   #15
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I'm sure there'll be someone along shortly who knows that engine intimately but I'd be surprised if the answer wasn't "full open"
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Old 26 August 2021, 20:19   #16
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A1o,
Just re-read your last and you mentioned "adjusting the vent". If you mean the air vent on the tank, that should be full open whenever the engine is running
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Old 26 August 2021, 20:44   #17
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Wasn't there something a little unusual about the seahorse in that it had the carb idle mix as a dial next to the choke and a sliding throttle under the pull?
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Old 26 August 2021, 22:17   #18
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Yes, that's the one.

Seem to remember some had a dial for the mixture, but the later ones I think had a little cap with a screw head under it.

Lovely engine - but that throttle was horrible.
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Old 26 August 2021, 22:26   #19
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Old 27 August 2021, 05:58   #20
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https://www.screwfix.com/p/no-nonsen...tle-1ltr/46908
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