15 HP Johnson overheat Q
 

On 13 Jul 2003 02:10:42 GMT, (BORDEN1000) wrote:

Greetings

I have a mid 70's era 15 hp Johnson that has been starting and running fine for
the past year. One year ago I replaced the water impeller.

Last weekend I idled down the river about 3/4 of a mile and the engine just
stopped. I looked back and smoke was coming from the engine. Oh
great...water impeller broke??? I paddled back to the ramp and pulled on the
cord. The engine would spin, but I didn't try to start. Back at the house I
ran compression and I am getting 55-60 on both cylinders.

So, aside from buying a new 4 stroke, what are my "home repair" suggestions?

Thanks in advance

BL


I have heat sized a 15 HP Johnson twice, and it still ran OK
afterwards. There was a destinct ring rattle, but it still ran fine.

This last winter I rebuilt it and replaced the rings, and a few other
pats not related to the heat seize. It now runs like new.

My advice is to replace the water pump/impeller and see how it runs.
You won't do any more damage than what's already been done....
Good Luck.

15 HP Johnson overheat Q
 

Joe Here wrote:

On 13 Jul 2003 02:10:42 GMT, (BORDEN1000) wrote:

Greetings

I have a mid 70's era 15 hp Johnson that has been starting and running fine for
the past year. One year ago I replaced the water impeller.

Last weekend I idled down the river about 3/4 of a mile and the engine just
stopped. I looked back and smoke was coming from the engine. Oh
great...water impeller broke??? I paddled back to the ramp and pulled on the
cord. The engine would spin, but I didn't try to start. Back at the house I
ran compression and I am getting 55-60 on both cylinders.

So, aside from buying a new 4 stroke, what are my "home repair" suggestions?

Thanks in advance

BL


I have heat sized a 15 HP Johnson twice, and it still ran OK
afterwards. There was a destinct ring rattle, but it still ran fine.

This last winter I rebuilt it and replaced the rings, and a few other
pats not related to the heat seize. It now runs like new.

My advice is to replace the water pump/impeller and see how it runs.
You won't do any more damage than what's already been done....
Good Luck.

Yes that's a good idea, 55-60 is not bad news as such because the numbers
depend on lots of things, not the least being the type of gauge you were using.

When you pull on the cord if you feel a distinct bouncy sensation on each
compression stroke, it should be OK & if you were only idling when it happened
------------------ certainly worth the trouble of a new impeller & making sure all
the water flow is clear.

K

15 HP Johnson overheat Q
 

Greetings:

I will check the impeller. If the impeller is OK, how do I continue to track
the problem??? Where is the thermostat?
What else can stop working to overhead the motor besides the impeller,
thermostat and plumbing lines?

Thanks

BL

15 HP Johnson overheat Q
 

Head gasket blown

"BORDEN1000" wrote in message
...
Greetings:

I will check the impeller. If the impeller is OK, how do I continue to
track
the problem??? Where is the thermostat?
What else can stop working to overhead the motor besides the impeller,
thermostat and plumbing lines?

Thanks

BL

15 HP Johnson overheat Q
 

BORDEN1000 wrote:

Greetings:

I will check the impeller. If the impeller is OK, how do I continue to track
the problem???

With the water pump & leg removed you should be able to push a piece of wire
up the pipe to make sure none of the rubber grommet has gone up there last time
the leg was put on.


Where is the thermostat?

In the water cover (bolted to the head) it's in the centre at the bottom, but
you can take the water cover off easily & clean any salt buildups etc out.


What else can stop working to overhead the motor besides the impeller,
thermostat and plumbing lines?

As another suggested the head gasket?? is there any water getting into the
cyls?? turn it over with the plugs out & make sure it remains totally dry.



Thanks

BL

K

15 HP Johnson overheat Q
 

Over 12 years ago my 1976 15hp had same problem. We installed a new
impeller, new themostat. Then only a drip out the peehole and still
overheating. Finally found the little o-ring at the top of the water
tube had crumpled and blocked the flow going into the head. This is at
the base of the head where your watertube from the foot inserts.
Get the Clymer Manual (B732)from Carquest Auto, excellent book.
Tough engine, still strong today, went 12 miles yesterday in salt,
don't replace! Give to me if you do.
Bill Mc

15 HP Johnson overheat Q
 

Greetings:

I will check the impeller. If the impeller is OK, how do I continue to
track
the problem???

With the water pump & leg removed you should be able to push a piece of
wire
up the pipe to make sure none of the rubber grommet has gone up there last
time
the leg was put on.


Where is the thermostat?

In the water cover (bolted to the head) it's in the centre at the bottom, but
you can take the water cover off easily & clean any salt buildups etc out.


What else can stop working to overhead the motor besides the impeller,
thermostat and plumbing lines?

As another suggested the head gasket?? is there any water getting into
the
cyls?? turn it over with the plugs out & make sure it remains totally dry.



Thanks

BL

Greetings:

Pulled the leg and the impeller is shot...byw, my local merc dealer sold me a
merc impeller...said it was a sraight replacement for the Johnson. Hmmm

I pulled the head and the cyl walls seem smooth to the touch. Each cylinder
has one very slight groove. A friend is supplying a cylinder caliper to
measure the dia of the cylinders...then I will spec / replace the rings and
give her a go.

Thanks for all the help
BL

15 HP Johnson overheat Q
 

Over 12 years ago my 1976 15hp had same problem. We installed a new
impeller, new themostat. Then only a drip out the peehole and still
overheating. Finally found the little o-ring at the top of the water
tube had crumpled and blocked the flow going into the head. This is at
the base of the head where your watertube from the foot inserts.
Get the Clymer Manual (B732)from Carquest Auto, excellent book.
Tough engine, still strong today, went 12 miles yesterday in salt,
don't replace! Give to me if you do.
Bill Mc


Greetings:

I have a second one w/ low compression in the garage also, so...if you need
parts, let me know.

BL

15 HP Johnson overheat Q
 

Over 12 years ago my 1976 15hp had same problem. We installed a new
impeller, new themostat. Then only a drip out the peehole and still
overheating. Finally found the little o-ring at the top of the water
tube had crumpled and blocked the flow going into the head. This is at
the base of the head where your watertube from the foot inserts.

Greetings

Is there a clever trick to make certain the tubes align into those rubber
grommets?

Thanks

BL