Another 1997 Force 120 Reeds problem

[blackd]

Put the boat into the water and tested WOT and response. Lost several 100 RPMs and was sluggish trying to plane. At the dock idle was erratic with sneezing. Thought maybe was from a combination of old gas, dirty carbs, and old plugs. I idled on muffs for few minutes in the back yard and idle got worse with more frequent sneezing.

When I cleaned the upper carb found it to be just fine, so decided (after researching here, thanks) to check the reed blocks. Wow! One reed in each the upper and lower blocks were nearly gone, and 1/2 of the total reeds showed this loss or chipping damage. I was able to rebuild two blocks by salvaging those remaining undamaged reeds, and ordered two used blocks off Ebay. Now, just waiting for the reeds and gaskets to arrive.

What's next? Been wrenching on outboards all Summer.

 

[pnwboat]

Hard to say what's next. Good that you found what you need. Don't know why, but the 1996 and later 120HP motors seem to have more reed issues than the 1995 120/125HP and earlier motors.

There are composite reeds available for the 1996 and later 120HP motors, but I don't know how long they last. Have to say though, I've seen many late 80"s 125HP motors with the original metal reeds.

 

[Frank Acampora]

I have seen these square-tipped reeds broken and it does seem to be a relatively common problem. Hopefully the used ones you put in will last longer. Pnwboat did mention composite reeds: They usually do not last as long as the Factory steel reeds BUT--- when they do break, they will pass through the engine without doing any damage. Were I you, I would take off the head and inspect the combustion chambers and piston crowns for pieces of reed stuck in them.

What next? Hate to be the bearer of bad news, but these engines all used a semi-keystone top piston ring. Again, these rings are prone to carbon and catch in the exhaust ports. When they break, the damage can range from minimal, requiring a piston replacement, to maximal, requiring a tear down, boring job and piston replacement.

I have a 150 with these pistons and rings and when one does go, it is my intention to replace ALL the pistons with Wiseco after-market pistons and rings.

BTW: Older round-tipped reeds from the 1970s and 1980s were five petals per reed vee block side and almost never failed. In fact, in about 35 years I have only seen one petal failure. NOW, the screw pattern on the vee blocks is different and the side tabs on the vee blocks are also a bit shorter BUT Since Merce never changed the relief in the manifold casting and simply added four more reliefs to accommodate the Square-tipped screws, you should easily be able to swap in the old style. I have gone the other way and swapped the square-tipped reeds for the round-tipped and found no increase in performance.

 

[Jiggz]

To add my 2 cents, you need to account for all the petals missing otherwise highly recommended you open and inspect the head including the crankcase ( through the intakes) for the missing broken petals. I highly recommend not using any of the petals remaining but instead replaced them all with new ones. And I mean replacing all 4 sets. Do a compression check before opening and inspecting the cylinders. This will give you an idea if you have bad rings.

 

[jerryjerry05]

Also setting the carbs after a good cleaning.
The air screw start about 1 and 1/2 turn out from lightly seated.

 

[blackd]

Thanks folks. I'll let you know how it works out

 

[blackd]

Here's the update. The reeds solved the sneezing problem, BUT, now it won't run well at all. Won't idle unless throttle is advanced. Smokes, and runs rough at high speed. All this is on muffs.

Compression is 147, 150, 150, 150 - 1 through 4. New plugs. Since it is running so rich, I am leaning toward the fuel pump, since it is still in original condition. I will re-check the lower carb to ensure the float is set correctly. I already did the upper. Both have been cleaned and set.

Still need to check spark and then what?

 

[pnwboat]

If it's running rich, double check the fuel primer solenoid. If it's stuck open, it'll dump excess fuel into the motor. It's only supposed to do that when you engage the choke. Just disconnect the small fuel line from the top carb. fuel bowl to the primer solenoid and plug it off temporarily to see if that helps. You can squirt some carb cleaner into the inlet fitting of the solenoid and push the black button on the top of the solenoid repeatedly and see if that fixes it if it is stuck open.

Probably wouldn't hurt to replace the fuel pump diaphragm like you said and double check spark.

 

[blackd]

pnwboat solved the major issue. Thanks!

I mis-connected the fuel primer feeds making it act as if it was stuck open. Now to do the fuel pump rebuild, just for safety sake, and check the ignition spark.

Otherwise the motor tuns much better, idles with minimal smoke and revs on muffs. I will put it into the water next week.

 

[pnwboat]

Looks like you've got all your major issues resolved. Hope all goes well next week.

 

[blackd]

Back from the on water test and things are still not quite right. Its not reaching WOT throttle. When goosing the throttle at the dock I got lots of smoke, so think it is now running rich at WOT. Things I did before going out, 1) rebuilt the fuel pump. 2) Reset idle speed. I did not double check that one carburetor, so float may be off. I did check that primer solenoid, and when I depressed the button engine stumbled. Anyone have any other ideas?

Also the battery died while I was testing. Another one is in the work shop, so will install that next.

On the plus side, the engine starts easier than it has in years. It idles really well. Doesn't smoke at idle. It's time to cut some grass so will put off many or the little checks for a few days.

 

[pnwboat]

I would double check the other carburetor. After you squeeze the primer bulb 5 or 6 times, it should get firm. If it doesn't, then you may have a needle valve that is not shutting off the flow of fuel to the carburetor.

 

[blackd]

pnwboat, the bulb does get hard, so don't think its the needle valve. It wasn't getting this hard before rebuilding the carbs. Wonder if I messed up the timing when I was setting idle. I messed with the wrong screw. Need to borrow a timing light, and double check that carb.

Thanks for responding. Chasing the gremlins in this motor (some made by myself) has been enlightening.

 

[pnwboat]

Yes definitely verify the timing.

Idle mixture screws should be set to anywhere from 1 to 1 1/2 turns out from lightly seated. My service manual says one turn out, but it varies slightly from motor to motor. Sometimes I get a lot of smoke when I goose the motor in neutral in the water. Depends......if I've been running the motor at low RPMs prior to hitting the throttle, I get more smoke than if I've been running at high RPMs.

 

[blackd]

Another gremlin identified. Put the timing light on the motor and found it set at ~10 degrees. Tried to adjust and NOTHING CHANGED. The only thing I can think of is the key has broken and the flywheel slipped. Anyone else have this problem? What was the fix?

At least it appears I have good spark to each plug.

 

[pnwboat]

A broken flywheel key is relatively easy to fix. Ace hardware has a selection of keys, or you can order a replacement.

Did you check the timing at WOT? At idle speed it's around 5 or 6 degrees BTDC but all the specs in the manuals are for WOT. There is a procedure for a static timing check with the throttle set to maximum speed and using the starter to spin the motor over without actually starting the engine.

 

[blackd]

Latest update as I chase gremlins in this motor. Took off the flywheel and found nothing amiss under it. I did mess up the timing when I was adjusting idle so got a timing light , remote starter, took the plugs out grounded the leads, and set timing at WOT at 28. While cranking the motor to adjust and set timing noted some light smoke coming from starter. So, a new starter is on order.

New plugs, rebuilt fuel pump, rebuilt carbs, used lower unit, soon to have new starter, and many hours working on checking and/or fixing these items. If it runs well after all this I will be pleased. I'm already more comfortable with the motor than I was last year, when I parked it for another boat. At that point I was afraid that the lower unit was broken. It was. The other boat is a whole other saga which is still to be written.

Old retired guys with old stuff and plenty of time and work space. ;-)

 

[Jiggz]

The old starter may still be good except it need some cleaning. Disassemble it (make sure you mark the orientation of the end bell or end plate with the body) and inspect the condition of the brush and commutator. Clean both using fine sandpaper and if you have contact cleaner (available at Radioshack) use it. Test again.

 

[blackd]

Well, the gremlins are still not quite gone. Installed the new starter and it made a huge difference. Battery doesn't seem to be totally down.

Put it into the water. Let it warm up. Idled away from the dock. Opened it to WOT, and ... it only went to ~2600 RPMs. It just wouldn't go any higher. Next week when its cooler I will put it back in the water and under load start checking things.

Any ideas?

 

[pnwboat]

1. First make sure that the throttle plates are pretty much in the horizontal position at WOT.
2. Check for spark on all cylinders.