1990 force 120hp outboard HELP!

puffitu

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New to this so bare with me.
Long story short; the engine ran fine last seven times I took it out. Yesterday, I noticed the temp gage acting up in high rpm, then loosing power/hesitating, then stalled. Couldn't get it started; almost as if the battery didn't have enough juice to power the starter. Before that day I had a mechanic do a compression test and the cylinders came in at 1=85,2=140,3=155,4=150. Today I tried to start it in a bin of water and same thing; on a fully charged battery-sounds like just not enough juice. so I tried to see if its seized manually and it was rather tough to turn the flywheel but got it to go. Pulled the plugs out and tried; perfectly smooth. Its got plenty of fuel, Checked plugs. Im thinking of replacing the impeller water pump thing and do a lower unit inspection since Ive not checked it since I purchased the boat about two months ago. Any advice will be greatly appreciated.
 

Tassie 1

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You've got a big difference in compression between no.1 and the other 3,
you have to see what the issue is there first,
 

puffitu

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Thanks,
the mechanic said to start looking for a Merc a couple of weeks ago when I had the compression test done. So I was aware . What do you think would be wise to do in this situation, first? When I turn the flywheel by hand without the plugs in, it turns smoothly but as soon as I put the plugs in it’s hard to turn. I also had a all the gages replaced; maybe a cross wire or grounding issue which contributed to the overheat? Is that a possibility? I also noticed that after I replaced the plugs maybe three weeks ago, the #2 plug was pretty fouled, which was odd. Am I getting water in the chambers?
 

jerryjerry05

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The difference in the compression is what's making the motor hard to turn.

Try pulling the head off and check for damage??
It could be just a bad head gasket??

#2 plug fouled could be the recirc system is clogged?

Location? fill out the signature and add a location.
You might be close to someone who can help.

If you change to a Mercury??
You'll need to get a new shifter and wiring.
Make sure the drive shaft is the same length.
 

puffitu

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Thank you!!
The dilemma I’m having to boot is that there are no decals or any ID on transom; so no idea what model motor this is. Maybe someone has some ideas as to how to identify this engine. Apparently it’s an original motor which is on a 1990 18’ welcraft. The boat and trailer are immaculate...the motor ran fine for the six or seven times I took it out; other than the fact that it would stall every once in a while but work in progress, right? Anyways, I would really appreciate if someone can help; I’m pretty mechanically inclined, I have manual, just not enough experience with marine propulsion. Also, I live in the Sarasota/Bradenton Florida area-maybe someone knows a good marine mechanic that won’t bend me over too much..haha
 

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SkiDad

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Have you verified spark ? I had a stator go our on mine - that is an electrical component under the fly wheel. It was good one minute gone the next. Replaced it and had many trouble free years after that. Of course don't replace it unless you do some troubleshooting/testing first. If you are not getting spark check out this website: https://www.outboardignition.com/support/176-3095.pdf
 

jerryjerry05

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With the compression readings??
Spark or not isn't really needed until he figures out why #1 is so low??
He said it ran then quit running.

The uneven comp readings on #1 causes the problem of the motor not turning over.

Like I suggested, pull the head and check the gasket and cylinder for damage.
 

puffitu

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I want to order parts for this thing but can’t seem to figure out what model number this engine is-any advice?
 

SkiDad

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1990 is a tough year b/c they were piecing them together from various sources. Most of the major parts were the same but electrical is dicey at best. What part are you looking for ?
 

puffitu

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Thanks Skidad, and to all who responded.
Ive got two different marine mechanics telling me that I should start looking to re power; one who actually did comp test etc. and another who after listening to me explain how the motor behaved before it overheated said the same and said I should get a Yamaha 90hp to re power. Now all that being said, I do not have the cash for a re power at this time but am willing to spend time and reasonable $ to get this thing running if possible. The thing is that Ive recently replaced the (Sierra)gages on the boat which were gifted to me from my dad who works for a gage co. Maybe a coincidence but the motor overheated and stalled right after I replaced gages(ive kept originals), after running for about 1.5 hours. I should also mention that it almost felt like the motor was fuel starved right before it died. I thought maybe the fuel/water separator so I went and replaced along with new squezzie thing because I thought it needed to be replaced and got fuel back into the system.
The guy who sold it to me had mentioned that the #1 cylinder had been hoaned or something to that extent. The previous owner also confessed that the boat sat for a few months so maybe a condensation issue?? As I said before the motor ran ok for six or seven times out but then after the new gages it suddenly overheated( I think) and died.
My position at this time is to check out what the comp loss is all about first. Change head gasket, check cylinders for damage while in there. Replace thermostat, water pump kit/impeller, check out the fuel pump diaphragm, gasket, maybe replace stator and any other items that you may suggest. Again, Im having a hard time figuring out what model/year motor this one is b/c the cowling says 120 on it. 120hp or 125hp? does this matter?? id be willing to bet this is the original engine and boat title says 1990 center console Welcraft.
Happy New Year to all and looking forward for your expert advice
 

jerryjerry05

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1990 was the first year for the 90 and 120
The impeller was the same on the 90/120
Before that it used a different one.

Before you buy any ignition parts??
Do a simple spark test.

Usually low comp has nothing to do with spark.

A cylinder with low comp could be caused by a few different things.
Over heating , bad gasket on the intake, recirculation system clogged etc.

You say your mechanically inclined, it's not that hard to bore and rebuild.

You can contact Wellcraft with the hull ID# and they can tell you what motor was originally
used on the boat.

You can find a used 85/90 120/125 up till 1993/4 and as long as the drive shaft is the same length??
It would be pretty much a straight swap.
From the pic, it looks like yours is a 20"

Post pics of the lower unit and ignition system we might be able to ID it from them.

Pull the head and take some pics.
 

puffitu

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Tech Tony

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The motor needs to have the low cylinder fixed, otherwise your throwing your money down the bog.
 

puffitu

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Thanks to all for advise. What’s the best and safe way to get seized bolts loose-I welcome any ideas!
 

jerryjerry05

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From what I see looks like mid year 1990 90hp.

To loosen seized bolts.
Head bolts: PB Blaster, a propane torch, and a hammer.
Heat the head, then along the side of the head and into the block.
The torch can heat the head and do no damage no matter how hot it gets.
An acetylene torch gets too hot and will melt the aluminum and you'll never get the bolt out.

Spray PB and tap with the hammer the top of the bolts ,heat and spray and repeat.
Then SMALL turns of the bolt, both ways in and out.

I've found that the bolt seizes in the head and not into the threads.
The galvanic corrosion from the dissimilar metals builds up and seizes the bolt.

I've worked hours and the bolt broke anyway :(
 

puffitu

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Thanks jerryjerry
really appreciate your input. I’ll try to monkey with it again bit later; it’s an everyday event. I had the lower unit off yeasterday and replaced the impeller/pump kit thing. Pretty easy; no major issues that I saw there. Began trying to get to the thermostat but only got 2/4 screws off. Going to check for spark today too.
 

puffitu

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puffitu

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