Alarm - Johnson 1989 115HP 2T (Help Needed)

CH1968

Petty Officer 3rd Class
Joined
Oct 15, 2007
Messages
80
All,


Just started my outboard (with ear muffs over water pump area) the first time in 18 months - after an extensive storage period of non-usage.

It ran fine (idle only) up to 3 minutes - then an alarm sounded at the console and i turned it off. I do not know if this alarm was caused by overheating or another tigger?

- the fuel is new.

- water pump/impellor is new (installed just before layoff in 2008).

- new thermostats and confirmed they open at the right temps (installed just before layoff in 2008).

- cleaned all cooling passageways, head internals in the block and exhaust area
- no cracks in cylinder heads.

- good / even compression from all 4 cylinders.

- fairly healthy water flow from **** hole.
- water does splash out from the propellor area.
- water supply pressure from tap not the strongest IMO.
- both heads were hot to touch.
- all water deflectors in block have been replaced and are not swollen.

It is noted that it is best to measure the temp at the cylinder walls, not on the cylinder head because there is very little cooling water around it. The head gets very hot normally and will burn your fingers.

I am using OEM oil mixing container which is connected up to motor.


Questions....

- best way to test ohms for temp sensors and in what type of oil bath?
- what temp/ohm triggers off the sesnors?
- how to determine if the water supply pressure is sufficient to prevent possible overheating?
- how to determine if this alarm is triggered by a strong vacuum in the fuel line or another cause?

- does a vacuum switch exist on this motor (if so where exactly)?
- where exactly are vacuum switches normally located on other motors?
- how to ensure I am not running my 2T fuel mixture too lean (hence too hot) ?
- exactly where at the cylinder walls should running temp. be measured?
- what is a good brand laser temp. measuring device?
- how to confirm if heat sender is faulty (causing alarm to trigger)?



Any advice on next steps to diagnose this problem would be much appreciated.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

Your cylinder heads should run between 143 and 150, at normal idle. You will get a hot horn once one/both head temp reaches 212 degrees- and won't silence till the temps get back down to 175. (still too hot) Once up on plane, the powerhead temps will go down, esp if you are running in cold water. You could borrow/rent a laser temp gun and see what actual temps the both heads run. Pull the two hoses off the thermostat housing and see what the water flow is exiting the block to the thermostat housing. If either of those new stats won't open, you can get an overheat at idle. If everything checks out ok, you might want to pull one/both cylinder head covers off the heads and inspect for debris/restrictions.
 

CH1968

Petty Officer 3rd Class
Joined
Oct 15, 2007
Messages
80
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

really good info there. much appreciated..

what is a good brand to buy - laser temp gun ?

i suspect i will be needing this tool more than once....

when you say "Pull the two hoses off the thermostat housing and see what the water flow is exiting the block to the thermostat housing."

i am assuming this activity is done without motor running?


Cameron
 

boobie

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Nov 5, 2009
Messages
20,826
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

You should also want to keep in the back of your mind that this mtr has water defelecters in the block underneath the cyl heads and if they get swelled up they can also cause an overheat.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

I paid something like $60 for my laser gun a number of years ago. A Craftsman from Sears. I have recently seen them down in the under $40 range. You can find a number versions of them in their special Sears Tool catalog.
 

CH1968

Petty Officer 3rd Class
Joined
Oct 15, 2007
Messages
80
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

You should also want to keep in the back of your mind that this mtr has water defelecters in the block underneath the cyl heads and if they get swelled up they can also cause an overheat.

thanks for this.

these water deflectors were replaced in 2008.

cameron
 

CH1968

Petty Officer 3rd Class
Joined
Oct 15, 2007
Messages
80
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

if i were to remove the bottom leg, what gear does the motor have to be in prior to dismantling?

Cameron
 

emdsapmgr

Supreme Mariner
Joined
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Messages
11,551
Re: Alarm - Johnson 1989 115HP 2T (Help Needed)

You might want to double check the year (model number) of your engine. OMC did not make a 115 in 1989, it was a 110 hp V4 that year. When you remove the lower unit, you will have to decouple the shift rod as it connects to the quick release shift mechanism under the bottom carb. Once you get into it, you will see how it comes apart and goes back together. It's a lot easier than the older ones where you have very limited access to unscrew the bolt to disconnect the rod.
 
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