1990 force 120hp outboard HELP!

[The Force power]

Good for you!
(I'm a little jealous of your location, I'm in the great white north and have to wait till the ice melts)

Now I'm starting to wonder about my options with my 90 HP???

 

[racerone]

Was the low compression on the one cylinder resolved ???

 

[puffitu]

YEs the comp numbers improved after head gasket, water jacket(bad shape) were replaced. Not perfect but workable! After being told to throw the motor in the dumpster by two different marine mechanics and then coming to this forum; I took on the challenge of repairing it myself even though Ive got no prior marine propulsion experience.

 

[puffitu]

Hey "may the force be with you"

Whats the issue with the 90hp? Maybe I got some insight..?​

 

[puffitu]

Hey all

I have a question that's been on my little brain in regards to the lower unit and lack of throttle in forward; only getting around 4400rpm WOT but not overly worried about it since the engine behaves WAY better after all the advise and info from this site.
On the lower unit; the shift rod which is threaded into the shift coupler. I have read in my manual (but cant find the info now) to thead it down finger tight at first then to back it out 4 turns for initial install. is this correct? Does this have an effect on the distance of the throttle throw, if the shift rod was threaded in too far??
Thanks ...

 

[The Force power]

Reply to Puffitu,

So far no issues any more, my motor is still on a stand as we still have freezing temperatures.(run in bucket in my heated garage)
I learned a lot on how to work on Force motors and I'm starting to get a grip on them(worked on many older Mercury)

To answer your question about the Shift-rod backing out 4 turns; I read that too in the manual, but they're referring to a two piece shift-rod???
when I Re-did my lower-unit (because I pulled the shift-pin/screw) I backed it out one full turn and it worked out just fine.
I don't think it will affect the distance of the throttle throw as it's fine threat & adjustment can be made after if necessary.
but boy; do NOT back it out completely or you'll be opening the entire lower-unit

as far as the RPM at 4400 I'm not there yet.....are the butterflies on the carbs completely open/horizontal?
when they over-turn & start closing due to over adjustment it would the same effect as not completely open

keep her going

 

[Nordin]

From factory service manual.
If you have a one piece drive shaft gearcase the lower shiftrod should be threaded all way down into the shift coupler.
If you have a two piece drive shaft gearcase the lower shiftrod should be threaded all way down into shift coupler and then back out four turns.

 

[jerryjerry05]

The butterfly's shouldn't move unless the throttle is moved or the
choke is activated.
They don't need to be flat when your at wide open, they can be past level
and not affect anything.

Shift rod: the 2 piece is the drive shaft not the shift rod.

If the rods adjustment is off and adjustment can't remedy any problems,
there is a double locking nut at the top of the shift rod that can be adjusted.
Hard to access, just remove the air intake baffle under the carbs.

 

[puffitu]

Thanks guys-
yeah, I don’t think is a carboration thing as I’ve went through the system and not much to it.
Thanks for the shift rod advise though
im not too worried about it; the engine is turn key after all the work and help from all you guys; Jerryjerry05 I definitely would buy a beer if I ever ran into him

 

[puffitu]

Thanks Nordin; I knew I saw that info somewhere.

 

[The Force power]

Thank you JerryJerry & Nordin for the correction on the shift-shaft and it got me to get out the factory manual to Re-read the topics I'd given "advice" on.
I did find in section 1C page 36 the position of the shutters/butterflies can affect the performance if not completely horizontal.
this of course can theoretically speaking but in reality not affect it as you said.

thanks guys, you are a wealth of information and greatly appreciated

 

[puffitu]

hey guys
How much water is this engine supposed to move when the water pumps working correctly? reason im asking is because this thing is moving a real lot of water; like gushing...kinda like kitchen faucet about 3/4 wide open. Am I only supposed to see a couple of peeing streams? or am I overthinking this..? and yes the thermo is in the right way...Thanks

 

[Nordin]

The holes at the back of the leg are idle relief holes and when idling a lot of water should come out.
When runing most of the cooling water passes through the lower leg through the center of the prop and the snout above the prop together with the exhaust.

The impeller is a low coast maintainance and I would suggest you to check it and if it looks worn....... just change it.

 

[jerryjerry05]

The earlier motors had a pressure relief system that shunted excess water out the holes
in the back of the mid section.
They found the system clogged up and the spring/plug seized and ended up doing nothing.
The later models 88up didn't use the pressure relief system.
They just left it open and plugged the hole.
The bad: the passages get clogged with crud and the flow is shut down.
If you run in sand/mud it clogs easier.

That said the pump is designed to push WAY,WAY more water than your motor can use.
I wouldn't worry unless you run in shallow water, sand or mud.

Beer?? just donate to the local no kill animal shelter.

 

[puffitu]

Hey thanks guys for all the awesome info! I’ve already replaced the impeller and housing. Running out of things to repair haha. I’m actually on the boat now; all is functioning and engine is responding as per design, besides the fact I’m only able to get 4400rpm but I think it’s because the comp numbers aren’t the greatest-they’re closer to even yet somewhat lower than factory. The motor is 30yrs old so I’m happy with performance which was achieved from the beginning of this journey. Jerry; I don’t know if the animal take beer donations but I’ll def be looking for a dog soon as wifey is eyeing a pet.lol Thank you all! Cheers!

 

[jerryjerry05]

4400 could be the prop? overloaded boat?
What did the compression end up being?

 

[puffitu]

Comp numbers were
1@115+​

2@95​

3@120-​

4@120

THis was before decarboning and before I ran it on fresh and salt a few times. I am going to check them again; probably good idea. The 4400rpm is at WOT maxed out. Seems i dont have enough throttle. The prop cleaned up was a significant improvement-didnt see any markings on it except a "S" on it so Ill have to research a bit more to identify and go from there. I am noticing an issue with the tilt/trim so that will be my next assignment. ​

 

[jerryjerry05]

Let us knw the new comp #s??

 

[The Force power]

The holes at the back of the leg are idle relief holes and when idling a lot of water should come out.
When running most of the cooling water passes through the lower leg through the center of the prop and the snout above the prop together with the exhaust.

This is when its a dual port exhaust & when its a single port it come only out of the snout (I believe)
Less to no water comes out of the "relief holes" while in the boat is in forward motion, as it creates a vacuum at "snout" and/or Prop (a great way to regulate the back-pressure)

 

[puffitu]

Ok
i got tied up at work last couple days late so I’ll get the new comp #’s on here tmrw...