1994 Force 120 Low compression on top cylinder

[stakultexsun]

1994 Force 120hp on 1994 Bayliner 19'.
Serial #: 0E088651
Model #: H120412PX

reading 89psi on top cylinder, 149 on other 3. (old compression guage, but readings were consistant, but might be off).

My Dad took off the head, as we could see what appeared to be metal shavings in cylinder when spark plug was removed..metal shavings on spark plug.

So, my question(s) is: What tale tale if any signs do these pics show? The top cylinder, I refer to as cylinder 1, the head looks cleaner than cylinder 2, I'll call cylinder 2. cylinder 1 is the low compression, and has evidence of scoring and metal.

The head gasket looked good.

Any input will be appreciated. If we can/could find a good mechanic, he might pay for a rebuild, which I'm sure it needs...but this boat barely even gets used so not sure how much money he'll put into it.

Thanks in advance.

 

[racerone]

Well the motor needs to come apart.------Finding a shop to work on it might not be easy.-----Finding a rebuilt block might be the best option.----Need to find what caused this issue.----Or it will fail again.----Was water pump impeller replaced about every 5 years or so ??

 

[Nordin]

Cylinder walls scored then that is the issue.
120Hp 4 cylinder has 2 carbs, one carb feeding 2 cylinders.
Check the carbs if they are clogged.
Lean running will end up with scored cylinder.
If you can catche the score with your nails you need to rebore, if not you can go for new rings and honing the cylinder.

 

[racerone]

Rebuilt 120 HP powerhead is listed on line at $1990.-----Then you have to install a lot of parts from yours onto that assembly.

 

[stakultexsun]

Thanks all for the response/info.
Water impeller replaced every year before use. Some years it never got use.

Was wondering about it running lean. Since it is 1 carb for per 2 cylinders...was wondering how only 1 could run lean?

I really want to understand why this happened. Like racerone pointed out, it will happen again. It seems like recent damage.

Like Nordin, I was wondering...replacing only the top piston/rings. This boat only gets 15 to 20 hours per year of use at most. where was that block? I looked for some...but couldn't see any in stock.

 

[racerone]

I see now there are none in stock.------It does give you the idea of the coins needed to have a shop repair this.

 

[ErSa]

I am also wondering, as stakultexsun,
how can we (Chrysler owners) avoid lean running cylinders.
Are there any basic tips? Colortune?

 

[Redbarron%%]

That cylinder may not be scored, but the piston is burned. (At least I don't see any serious scoring, but a quick clean with a scotchbrite pad to clean the crud and aluminum off.
If not scored then a piston would take care of the issue. What is the piston size. usually stamped on the top often this old a +0.030" I have some +0.030 used pistons that might help.

 

[Nordin]

Well I looked closer to your pics and if you compare the top of the damaged piston with another piston you can see the top cam baffle is affected and the whole piston top too.
This often depend on pre detonation.
I would suggest you to clean the carbs and check the timing advance at WOT.
From factory in those days they were manufactured it was set to 32 dg. BTDC.
Nowadays with worse fuel with more ethanol in the fuel it is better to retard the timing advance to 30 or 28 dg BTDC at WOT.
When tuning the carbs set the air/fuel mixture screw not leaner then 1 turn out from lightly seated. Better to have not so good idle than risk to melt a piston.
See Frank A:s link and sync post at the top of this site.

 

[stakultexsun]

thanks all for the responses. I haven't seen a label stamped on...other than what looks like a "B", but I can't really tell.

I see what you mean about the timing Nordin, thanks for that. Putting that in my memory bank..lol. This ethanol fuel is rough on stuff.

 

[The Force power]

Was wondering about it running lean. Since it is 1 carb for per 2 cylinders...was wondering how only 1 could run lean?

The #1 (top) cylinder likely is getting (slightly ever so slightly) less fuel than #2
So if #1 Carb is set lean and/or too lean if would be noticed first at #1
Also #1 cylinder is being "cooled" with water that has passed by #4 thru #2
in other words pre-heated water resulting in higher cylinder temp.

 

[stakultexsun]

The #1 (top) cylinder likely is getting (slightly ever so slightly) less fuel than #2
So if #1 Carb is set lean and/or too lean if would be noticed first at #1
Also #1 cylinder is being "cooled" with water that has passed by #4 thru #2
in other words pre-heated water resulting in higher cylinder temp.

Thanks for this input. These are two of the things I wondered about myself. I want to understand/diagnose this root cause.

Regarding the potentially lean due to carb #1, it seems they should get equally lean, or very close to it. So let's say carb # 1 is running 80% of the fuel it should be...
Are you saying cylinder 1 might be getting 70% of the fuel while cylinder 2 is getting 80+%? If so, how/why?

I also wondered about Cylinder # getting the "sloppy seconds" water from 4 thru 2 also. In addition, was thinking that when engine is off, does water drain out or is # 1 the last to get water and and first to have it taken away?
Thanks again.

Side note: My father has taken it to another mechanic, we'll see.

 

[jimmbo]

A leaky upper Crankshaft Seal or Bearing Cage Seal, can cause a leanness in the Top Cylinder

 

[The Force power]

Regarding the potentially lean due to carb #1, it seems they should get equally lean, or very close to it. So let's say carb # 1 is running 80% of the fuel it should be...
Are you saying cylinder 1 might be getting 70% of the fuel while cylinder 2 is getting 80+%? If so, how/why?

It not the actual Carp. not equally dispersing the fuel equally but the amount of fuel going in is also affected by the valve-reeds for each cylinder. Also the recirculation hoses that handles the unburned fuel have an effect on the cylinders (mostly on the bottom one, when its being re-introduced to the engine

I also wondered about Cylinder # getting the "sloppy seconds" water from 4 thru 2 also. In addition, was thinking that when engine is off, does water drain out or is # 1 the last to get water and and first to have it taken away?
The cooling-passage starts at the bottom & end at the bottom, so yes the top is dry first

jimmbo brought up a very good point, that got me thinking to check the gasket on the starter-side & reed-valves

 

[stakultexsun]

Update: Thanks again for all the input. Due to time constraints my father took it to a different boat mechanic. Not surprisingly, he says it needs full rebuild. Our biggest concern is getting a good job done. Don't mind paying good money for good work.

He quoted $5400 ish, which is more than we hoped for, but if he does a good job, than it will be worth it. He says he will of course. That includes everything, including boring it out to 3.375" (think it's 3.30" right now).

Crossing our fingers!

I'm relatively sure the last mechanic actually caused this failure by not having the timing correct. Though it has only ran for maybe 2 to 4 hours since the mechanic replaced the stator and all that. he kept messing with the timing and all that. Do you think it could go from being ok to that damage in 2 to 4 hours?

 

[racerone]

Opinions vary on this topic.----I would simply pick up a bad Johnson / Evinrude 115 HP for say $200 or so.----Rebuild that.-----In my wildest dreams I would not spend $5400 on that motor.----Well , maybe $1500 to replace 1 piston with O/S one !!

 

[Nordin]

I would not put 5400 dollar in a used 30 years old engine.
If they want to charge your 5400 dollar for a rebuild.....no, no, no.
They are cheating you. Rebuilding one hole with a new piston, rings and rebore is about 250 dollar then the cost in time to disassemble and reassemble the engine.
The cost in time to do that I can not estimate, but not about 5200 dollar, that is for sure.

 

[stakultexsun]

thanks for your inputs. Trust me, it was a debate. Time is so short in more ways than one as we all know.

$3840 of that is labor. labor rate $120/hour. 32 hours I guess. That sounds about right. Guessing it would take me 3x that. What do you say about 32 hours?

He entertained buying a newer boat, spending maybe UP TO $15,000 or so. Even with that, you get a newer boat, but you never know what you may end up getting.

This boat is in very good shape for a 1994, it has been garage kept it's entire life. It could use a new interior, but even that isn't bad.

We'd need to find that motor, rebuild it, then put it on, etc... I can't see how that would save that much, particularly if we're hiring someone.

Again, time. I want to and thought about exactly that...but man! Time time time...lol.

 

[racerone]

I say 20 hrs is reasonable.-----I say do this job yourself .----Or find a reputable dealer and get a rebuilt motor ( Johnson / Evinrude ? Mercury with warranty for those kind of coins!!

 

[stakultexsun]

And if this was the end of this summer season, would be less likely to pay someone, maybe more likely to attempt ourselves. Boat has already been down for over 1 year.

My father is 2.5 hours away from me, he has an RV park and 25acres of land. He can work 80+ hours a week and not get everything done, not for several months, maybe longer. Our time would be better spent doing that work rather than boat.