Another Guy With Force 120 Issue

[Popeye_1990]

Greetings. Ive read many post here regarding force 120 overheating alarm issues and tried a couple of fixes I have read. It seems like there's no pattern to the alarm sounding. Motor run strong. Sometimes sounds at idle coming off power, sometimes sounds on power. I added a tell tale and new thermostat. Run boat on lake on and off power from idle, neutral, up to 4600 rpms for over an hour....no alarm. Went next morning and didn't make 100 yards before alarm sounded on power. Backed off and powered up again and alarm went off. Run for about 5 minutes up lake, went to idle....alarm sounded for a couple of minutes them went off. Motor streaming lots of water 120s and below temp from tell tale and from rear ports. Today, alarm sounded on power, went to idle alarm went off. Did temp check on all cylinders next to plugs while at neutral with temperature gun. Top 3 cylinders in 130s degrees....bottom cylinder 167 degrees.

Any advice where to look? Are top 3 cylinders temp normal? What may causing such a difference in bottom cylinder? I appreciate any input.

 

[jerryjerry05]

You say you have a 120 any idea of the year??
Your thermo: 130d it opens.
Wonder why the bottom cyl. is 30d hotter?
Is there a thermostat in there?
Pull it and see how corroded it is? Throw it in a pot of hot water and see if it opens right?? Any crud on the thermo? it(crud) will settle down around the bottom cyl. cooling passages and will make it run hotter.
No way to check the passages unless you pull the powerhead.

 

[las]

Maybe running lean on number4?

 

[Popeye_1990]

You say you have a 120 any idea of the year??
Your thermo: 130d it opens.
Wonder why the bottom cyl. is 30d hotter?
Is there a thermostat in there?
Pull it and see how corroded it is? Throw it in a pot of hot water and see if it opens right?? Any crud on the thermo? it(crud) will settle down around the bottom cyl. cooling passages and will make it run hotter.
No way to check the passages unless you pull the powerhead.

Sorry. Year 1990
Thermos is 130 and new works as it should.
Would blown head gasket be the culprit?

 

[Popeye_1990]

Sorry. Year 1990
Thermos is 130 and new works as it should.
Would blown head gasket be the culprit?

PS ...only thermo is at top of motor above yoo plug...thanks jerry

 

[Popeye_1990]

Maybe running lean on number4?

If lean on number 4...how can I check that?
Thanks had not thought of that

 

[las]

If lean on number 4...how can I check that?
Thanks had not thought of that

Well I don't know the engine, but does it have 4 carbs?
If so you could adjust the carb to run a little richer than the others by turning the idle mixture on that carb and then measure temp again while running it like you did.
Could be many reasons for a lean condition, but adjusting idle mixture could give you an answer if your on the right path or not.

 

[Popeye_1990]

Well I don't know the engine, but does it have 4 carbs?
If so you could adjust the carb to run a little richer than the others by turning the idle mixture on that carb and then measure temp again while running it like you did.
Could be many reasons for a lean condition, but adjusting idle mixture could give you an answer if your on the right path or not.

Only 2 carbs. All 4 plugs are new. Gonna go pull them and compare them soon. To run richer...i back adjuster out right?

 

[las]

Yes it should be backed out to richen the mixture.
Maybe take a note of what it's base adjustment is, from lightly seated. Then run the engine and screw it out till the engine starts running rough, then a hair back and try it out and see what temps you got.
If nothing else it's a starting point in your troubleshooting, let's hear what your findings are!

Like I said I have zero knowledge of this engine! Maybe they doo tend to run hotter on no. 4? Is the overheat sensor placed near 4?

 

[Popeye_1990]

Location of alarm sensor...that is one this g I have tried to find out with no success. Really need that info if anyone knows. View a few videos regard overheating issues. In combination with what Jerry said...gonna bring boat home and pull exhaust cover and tale a peek inside. I'm a school teacher and there's just never enough time. Watch for post...back in touch soon.

 

[Popeye_1990]

Location of alarm sensor...that is one this g I have tried to find out with no success. Really need that info if anyone knows. View a few videos regard overheating issues. In combination with what Jerry said...gonna bring boat home and pull exhaust cover and tale a peek inside. I'm a school teacher and there's just never enough time. Watch for post...back in touch soon.

Haha...one more thing. Forgive my spelling and grammar. Texting from cell phone and my old thumbs are not my kiddies...

 

[las]

I haven't seen anybody bash anybody on this forum over grammar, and that's nice! We are quite a few people from other parts of the world getting the spelling and grammar wrong all the time. But as long as people get the meaning, I think it's fine.

 

[Popeye_1990]

Plugs from left to right are top to bottom. All seem very good. 4 the bottom has a little residue on bottom of threads but still very clean. Don't think this is it.

 

[Popeye_1990]

I believe this is thermo sensor. Between plugs 1 and 2. Good distance bottom cylinder. Gonna pull exhaust cover this evening. Pray don't break bolts and see inside.

 

[las]

First, did you clean the plugs after taking them out? Or did you change their position earlier. The one on the left seems odd compared to the others, and the others seems strangely clean on the surface?

The sensor could be faulty, but you do know now there's a difference and need to fix that somehow.

 

[Popeye_1990]

First, did you clean the plugs after taking them out? Or did you change their position earlier. The one on the left seems odd compared to the others, and the others seems strangely clean on the surface?

The sensor could be faulty, but you do know now there's a difference and need to fix that somehow.

Yes. I wiped them all except number 1. I cannot read this style plug without the electrode and tip. Gonna attack exhaust cover next.

 

[puffitu]

Really dial in your fuel mixture, and…when I had that same year force 120hp I also noticed that it would tend to like NGK BUHX PLUGS over Autolites and I even tried Champion UL18V’s but ended up back to the NGK because of the results I was getting. Compression numbers?? You mentioned blown head gasket?

 

[puffitu]

You running strictly in fresh water or salt

 

[puffitu]

Sensor may be faulty as well

 

[Popeye_1990]

Sensor may be faulty as well

Thanks. Had champions before could not find them around here.

Right now only in freshwater. Get things straightened out wanna hit inland new here.
Was curious if blown head gasket could be at root of #4 heating up so much than others. Gonna pull exhaust cover and see if debris is issue. If not...will go into head.
Do buzzers fail?