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tony bruce
02-29-2008, 05:47 PM
hi..tony from new zealand...found the forum after trolling around looking for help with my 15 hp 2stroke johnson which runs...but...has "issues"
from cold...she starts first/second pull..with choke...idles ok...then seems to run fine...gets my 3meter inflatable up on the plane quickly and runs well..
but..after a few minutes ...she progressively looses power and goes off the plane...won't idle...will not come out of forward to neutral easily on gear lever... then stops/stalls and will not start again .
if left for 1/2 hour or more she starts and the same thing happens again..
the motor "smells" hot...but telltale /impeller has good strong flow...
so...is the exhaust blocked???is there a port that may be blocked at the prop???or similar???
anyone out there that can help me with this???

i live 60 k away from nearist johnson dealer and hope to avoid having to truck motor into the city...

thanking you for any help ...tony

88 PS190
02-29-2008, 06:00 PM
This is really beyond the scope of this site, being that you have a 15 hp johnson outboard, and these boats are all inboard or 200+ hp outboard engines.

What year engine is this? An older engine carburated? I would wonder if your tank has its vent closed and is therefore building up vac and starving for fuel.

If you think the engine is overheating and the impellor isn't bad then I'd look for plugged passage ways.

But really these engines are simple, if the exaust were blocked it would not run. period.

Check the basics, air, fuel, spark.

Most of these engines smell hot, because they have to be fairly hot to combust cleanly.

But really, this is not the website for outboard motor repair. ha ha.

Prostar Rich
02-29-2008, 06:11 PM
What model year is the engine?

Prostar Rich

Sodar
02-29-2008, 06:17 PM
I would wonder if your tank has its vent closed and is therefore building up vac and starving for fuel..

First thing I thought of! Nice job!

88 PS190
02-29-2008, 06:25 PM
First thing I thought of! Nice job!

not my first time fiddling with outboards,

In our garage there are saw horses with about 10 of them, in the basement a few in boxes, in the shed a few leaned against the wall.

They are everywhere.

Old johnsons, waterwitches, montgomery wards, etc.

My dad loves those things.

flipper
02-29-2008, 06:33 PM
I've seen them do that when the motor has low compression, when it gets warm the compression goes down even more causing problems once hot.

Prostar Rich
02-29-2008, 06:37 PM
With a 15 HP he probably has a 6 gal can for a tank. Check the hose and the hose connections. Depending on the year there may be a screen in the fuel line right by the carb. There is 4 screws that need to be removed and be careful of the gasket. Check the screen.

Prostar Rich

stuartmcnair
02-29-2008, 06:47 PM
it's fifteen horsepower...go out in the water...detach it...drop it in the water...go to store...buy a new one...should run fine after that

flipper
02-29-2008, 06:56 PM
:uglyhamme :uglyhamme :uglyhamme :uglyhamme

your killin' me

tony bruce
02-29-2008, 08:17 PM
hi guys...i realise you are all M/C guys ..but thought someone out there may be able to help...
motor is S/H 1994 15HP# J15RERE...
tote tank has vent fully open...screen clean
sorry i'm killing you flipper

Maristar210
02-29-2008, 09:04 PM
Tony,

You are experiencing a loss of compression after warm up. Use a compression tester to verify. Once the motor warms up the components contract and it runs like and old slug.

New Rings mate, new rings !!!!!

flipper
02-29-2008, 09:18 PM
Tony,

You are experiencing a loss of compression after warm up. Use a compression tester to verify. Once the motor warms up the components contract and it runs like and old slug.

New Rings mate, new rings !!!!!

That's what I'm thinking. Not a hard job on a two stroke either.

flipper
02-29-2008, 09:19 PM
it's fifteen horsepower...go out in the water...detach it...drop it in the water...go to store...buy a new one...should run fine after that

Oh, and this is what was killin' me, not you.

rob935
03-01-2008, 08:47 AM
had the same issiue with a yamaha 15 horse power a few years back after 3 trips to the workshop turned out to be a crack in the cylinder , traded it in against a brand new one with a different dealer and have had no trouble since, old used 2 stroke outboards are a real head wrecker and waste too much valuable boating time. do yourself a favour and buy a mastercraft...!!!

kurtr
03-01-2008, 02:28 PM
Most of these outboards have a crankcase vacuum operated fuel pump; I have seen engines that will act like this when the fuel pump is not working properly. You could attempt to pump fuel into the engine while it is running by using the squeeze bulb. You could pull the choke on to see if it is running lean on fuel. Most of the time these fuel pumps are mounted on the side of the block and easy to rebuild or replace.