Johnson 4HP questions

Beakster

Petty Officer 2nd Class
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Jun 14, 2021
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Hi all,

Got myself a 4HP 2 stroke today, and an 8 foot fibreglass dinghy. I put the motor on and threw her in the water but she wouldn't start. However I didn't have any tools and it was getting dark so I'll start trouble shooting in a bin tomorrow. It hasn't run in 4 years but I'm told it was perfect when last run. So I'll start checking for spark, then fuel, compression etc.

This is my first small outboard and dinghy though so I got some questions. There's 3 seats in the boat. I can only reach the outboard from the rear seat but it feels like I should be sitting in the middle for stability. The tiller arm is very short and the throttle control is on the other side of the motor. Is this the right motor to be using with this type of boat?
 

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Crosbyman

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try using a longer fuel line and put the fuel tank up front.

not to many solutions other than balancing the load or moving up to a larger boat and OB with remote controls and steering :)
 

airshot

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If it hasn't run in 4 years, the carb will need a clean and rebuild with new gaskets. Get a factory rebuild kit so you get all the needed setup information to start. Clean out fuel tank, check hose and fittings to be sure they are still good. New spark plugs will only help, but check spark to be sure ignition system is good and healthy. Small boats require proper weight placement to be stable. As mentioned, get that fuel tank forward, you are probably required an anchor for safety so that can be moved as well.
 

jimmbo

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Pretty much every Used Engine I have ever seen as been described as running Perfect the Last Time it ran, even the Ones that had Broken Piston Rings, and even a Hole in the Crankcase...

First things first.
Is there Oil in the Gearcase?
I would suggest an Inspection of the Water Pump, and a New Impeller at Minimum.
What are the Compression Numbers?
Can the Ignition System provide a Spark that can jump a 1/4"-5/16" gap, on both Plug Wires?
Is Fuel getting to the Carb? Is it going into the Fuel Bowl?
If you have decent Compression and Spark, You can try spraying a bit of Premix(50:1 TCW-3) in the Carb and see if it fires
 

Nordin

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Do as Jimmbo says check compression and check for spark.
The spark should jump at least 1/4 in in atmosphere.
The ignition coils for these old OMC engines had a tendency to crack over time and dry out. They can create spark but when under load it will fail.
Pull the flywheel and check those coils.
 

saltchuckmatt

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Assuming the motor is running good, I usually layout as forward as I can until it gets on a plane then slowly move back and sit. If it's a light little boat it my get "squirly" so be careful

Tiller extension is what I use on my 12 aluminum boat.

Google it up or make your own. Obviously the throttle is a problem.
 

airshot

Rear Admiral
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Easy to make an extension for the throttle lever, not an ideal situation but very doable. Not sure it will plane with only 4 hp, but should be a fun little boat to play with.
 

Beakster

Petty Officer 2nd Class
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Jun 14, 2021
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Thanks for the advice so far. I confirmed there was spark then took the carb off and cleaned it out, although it looked pretty clean. Put it back in and still couldn't get her to start in the bucket.

I then used a drill on the flywheel and played with some of the settings and I got her started and running nicely.

Question I have now is how do I correctly set the middle position for the rich/lean fast and slow knobs? And how should I be using them when running the outbound?

Thanks
 

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Crosbyman

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go on the lake get heengine at operating temp. run full throttle and lean out CW till it starts to sputter then enrich CCW till it sputters go mid point slightly richer than leaner

GO idle and do the same.
remove the knobs ONLY do not turn needles ... center the knob pointers and install. tighten the needle collars to prevent shaking and looseneing of the needles...
don't touch after adjustments are finished.

to learn about these little 2 cyl JWs 3-4-5hp OBs you should get a copy of the johnson service manual which explains all you need to service your kicker

https://watercraftmanuals.com/outboard/johnson/manuals/johnson-302231.htm
1715806893364.png
 
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Beakster

Petty Officer 2nd Class
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Jun 14, 2021
Messages
113
Thanks. I also found a large online which I've used and she seems to be starting and running quite nicely.

I'm disappointed with the speed though. I'm only managing 5knts in my 8 foot fibreglass dinghy. Is that to be expected?1000011053.jpg
 

Beakster

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113
The 6 to 8 hp series is the best. I love the 87 with the primer a no choke.

Matt
Here are the specs of my dinghy
Length: 8 ft. 3 in. / 2.50 m
Beam: 4 ft. 6 in. / 1.37 m
Draft, board up: 0 ft. 4 in. / 0.10 m
Draft, board down: 2 ft. 4 in. / 0.70 m
Displacement: 75 lbs. / 34 kg

What HP would I need to plane? There's a 6HP for sale near me, would that do it?

Is the 8HP much heavier?
 

saltchuckmatt

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What year is the six? Most likely that's all you need. I like about the 82 on up....older ones are fun to work on and then put them out to pasture. (Wall)

Most 6 thru 8 are the same weight. Carb and restrictor plate. Best not to fool with them.
 

Crosbyman

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What year is the six? Most likely that's all you need. I like about the 82 on up....older ones are fun to work on and then put them out to pasture. (Wall)

Most 6 thru 8 are the same weight. Carb and restrictor plate. Best not to fool with them.
Matt... much to harsh on the 70,s 6hp ... lovely machines with TLC they run forever ! All that saltwater is killing your oldies but up here in the great North with all that fresh water those 6hp last foreever :) but we don't catch 40-50 pounders much .
 

saltchuckmatt

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We have millions of old 6 HP motors. Our water in Puget Sound is brackish so low salt.

I like to go boating when I want to go boating. Playing with carb settings while taking say a grand daughter fishing is not what I'm into.

I was merely telling him which motors are the best or at least what I think is the best, which is the question he was asking for.

Tim, I agree. Looking at the pictures that looks like those plastic boats that they sell at West Marine here in Seattle and they're really kind of rowboats, or both that you would use from your yacht into the land and a four horse would be perfect.

I bet if you got that thing up on a plane it'd be so squirrely that you tip over if you just tried to turn.

Could be wrong of course.
 

tphoyt

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Jun 10, 2010
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Correct. It has a displacement hull or could even be considered semi displacement at best. They are intended to carry more weight and be a bit more stable going to and from land and your big boat.
That type of hull has very little lift so getting it on a place is not easy.
 
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