1987 85hp Force outboard idle questions

[lowvlot]

It has been a while since I have been on the forum. My rebuild is complete as far as the boat is concerned and now I have moved on top the power plant.
The other day I decided to be a "mechanic" and try to adjust my carbs as I thought it was running to rich. I downloaded the manual for the engine and went to work. There are three carbs and I adjusted them according to the manual. However, when I tried to put it in gear it would die. I then adjusted the screw in the picture. Let me cut to the chase. What is this screw for anyway? I took the boat out yesterday and it ran great for about 15 minutes then died. It starts right back up and will remain running as long as I don't throttle it past about 10 miles an hour. Also, when in neutral the idle is extremely fast. Can anyone tell me what is wrong and what that screw is for?


Thank you in advance.

 

[Frank Acampora]

AHHH! CARBS! They hang out front like women's breasts and men just have to play with them. The result is usually the same as grabbing or groping a woman.

Adjusting the carbs according to the manual will usually result in them running too lean. Typically, you would set the low speed needles to about 1 1/4 turn out from lightly seated and adjust from there to no less than one turn out--no matter what the idle quality. Then use the idle stop screw on the timing tower to adjust idle to 700-750 RPM in forward gear, in the water.

Now, run a compression test on all three cylinders to see if the engine is still mechanically sound inside. Then, if it is sound, do yourself a favor and watch my video at the top of the forum. Also read the sticky: FAQS--Synchronizing carbs and timing.

 

[lowvlot]

So is the screw referenced in the OP the idle stop screw?

 

[lowvlot]

There is a cover covering the carbs on the back side. can I remove this without ruining something? is there a gasket I will need to replace?

 

[SkiDad]

the screw that is near the flywheel is the timing screw - if you changed that you messed up the timing - if you adjusted the one all the way at the bottom then that is the idle. If you are referring to the 2 black covers in front of the carbs with 3 flat head screws in them, then yes those can come off

 

[lowvlot]

No Title

This screw

 

[Frank Acampora]

Yes, that is the idle stop screw. IT is the way you set the idle speed AFTER timing and low speed needles are set correctly. If you change propeller pitch, it may also need to be reset since higher pitch propellers load the engine more in forward gear than lower pitched props do. Screwing this screw too far in will raise the idle, but may also eliminate the fast idle position. Typically, this happens when you go to raise a too low idle because of timing or carb settings or even low compression.

The air box covers all three carbs held on with two screws through each carb. It can be removed with no ill effects. At the bottom is an oil recirculation hose. It enters the bottom of the manifold through a metered fitting so the hose can be disconnected with no harm to the engine. There is a separate gasket at the face of each carb. When replacing the air box, these three gaskets must be in place and correctly oriented. If installed sloppily, these gaskets can interfere with the operation of the choke butterflies

 

[lowvlot]

Yes, that is the idle stop screw. IT is the way you set the idle speed AFTER timing and low speed needles are set correctly. If you change propeller pitch, it may also need to be reset since higher pitch propellers load the engine more in forward gear than lower pitched props do. Screwing this screw too far in will raise the idle, but may also eliminate the fast idle position. Typically, this happens when you go to raise a too low idle because of timing or carb settings or even low compression.

The air box covers all three carbs held on with two screws through each carb. It can be removed with no ill effects. At the bottom is an oil recirculation hose. It enters the bottom of the manifold through a metered fitting so the hose can be disconnected with no harm to the engine. There is a separate gasket at the face of each carb. When replacing the air box, these three gaskets must be in place and correctly oriented. If installed sloppily, these gaskets can interfere with the operation of the choke butterflies

You are a wealth of knowledge, thank you.
How would I, a guy with limited knowledge of engines check compression? Also it looks as though my engine has the tick marks for timing but I do not have a timing light or the know how to use one. Thoughts on this? How am I to know if I have the carbs adjusted correctly or the idle speed? I feel lost here.

 

[Jiggz]

You need to tackle your concerns with the motor one at a time instead of trying to cover it all at once. The first thing is to find out if the motor has good compression to start with. Here's is a video on how to do it. Note, the video did not explain the requirement of grounding the spark plugs to ensure it does not create a problem with the power packs.

If compression numbers are good (within 10% of each other with a minimum of 90 psi - very subjective due to difference in gauges) you can check timing. There is a video in one of the sticky posts (first posts on this forum) that explains a detailed step by step process to do it.

After timing, then set you "link and synch" which is also explained in one of the sticky posts. From here we can start doing some targeted troubleshooting for any problems you may have with the motor.

As for the tools needed, compression gauge and timing light, you can either rent one from Auto Zone or buy them from any auto parts store. I believe Harbor Freight also has the timing light but not sure about the compression gauge.

 

[lowvlot]

You need to tackle your concerns with the motor one at a time instead of trying to cover it all at once. The first thing is to find out if the motor has good compression to start with. Here's is a video on how to do it. Note, the video did not explain the requirement of grounding the spark plugs to ensure it does not create a problem with the power packs.

If compression numbers are good (within 10% of each other with a minimum of 90 psi - very subjective due to difference in gauges) you can check timing. There is a video in one of the sticky posts (first posts on this forum) that explains a detailed step by step process to do it.

After timing, then set you "link and synch" which is also explained in one of the sticky posts. From here we can start doing some targeted troubleshooting for any problems you may have with the motor.

As for the tools needed, compression gauge and timing light, you can either rent one from Auto Zone or buy them from any auto parts store. I believe Harbor Freight also has the timing light but not sure about the compression gauge.

I have been doing my homework. From what I have seen, you can just jump out the starter wire instead of using the key. Thus eliminating the need to ground the plug wires. Is this correct? Also, there seems to be some confusion out in the world as to if you only remove the plug your checking compression on or all of them. Can you enlighten me?

 

[foodfisher]

All of them. Be sure to ground them. Sounds like you're into DIY so an OEM manual should be your first tool purchase.

 

[lowvlot]

Okay. I have done the compression test.
First cylinder comes back at 105
Second cylinder comes back at 104
Third cylinder comes back at 104
I am assuming this is good.
Next?

Edit: May have to do it again. I wasn't WOT. Does it make a difference?

 

[foodfisher]

Low but within the 10% range. Could be old age or carbed up rings. Try a different gauge or a decarb.

 

[Jiggz]

Readings are good and are within 10% of each other. Now do the timing check and then followed by link and synch. After the link and synch, unless there is problem with the motor, it should idle perfectly around 900~1000 on muffs. If such is the case, then it is time to take her out for a spin.

 

[lowvlot]

I ran the test again with WOT. All three came back at 105. Going to check timing tomorrow. I will report back. Thank you all.

 

[Jiggz]

Contrary to popular beliefs, doing compression test with WOT or Idle position is irrelevant. Unless, you have the boat submerged in the water (even this is contestable since the relief exhaust ports are also open to atmospheric pressure. Otherwise the cylinder always goes on atmospheric pressure when piston goes bottom dead center because the exhaust port opens to the atmosphere.

 

[lowvlot]

Well, I got a timing light and checked the timing. It was out but not by much. If I did it right, it should be in time now. The carbs are synced as far as following the video in the sticky goes. Still not sure about mixture though. How do I know when I have it right? should I be worried about checking to make sure the coil packs are okay? If so, how would I go about this?

 

[Jiggz]

For the idle mixture screw, just set it at 1 turn out for now. This is just initial setting that will ensure you have enough fuel to start the motor and also enough lubricant to ensure proper lubrication. Well, if you think you have it synch already, go ahead and start it and see where the idle speed is at or if it will even idle. Do you have a tach? If not you need to invest in one or get a photo laser tach (about $15) from *bay or get an induction type Tiny Tach. The idle rpm (neutral) should be around 900~1000 on muffs.

Note, don't try to achieve this rpm by screwing the idle screw all the way in, which is an indication the motor is probably not firing on all cylinders. If this is the case, you will need to find out which cylinder is not firing by quickly pulling on each plug wire and listening to the engine tone. Note, there is possibility of damaging power packs if you keep the plug wire off for an extended period of time. Re-insert wire as soon as possible if no change of engine tone is recognized.

If you are not confident on pulling plug wires, buy an in-line spark tester to see if all plugs have sparks. If they do then the next move is to find out which cylinder is not firing (due to fuel related problem) is to do the spray bottle test. This involves removing the carb's air cover and while the motor is idling, spray fuel-oil mix directly into each carb and listening for change in rpm. The carb that increases rpm is faulty while the carb or carbs that bogs down the motor are working properly.

 

[lowvlot]

Took her out today on a bit of a test run.
I have to say, I am not sure she has ever ran this good, however, she didn't seem to really get up and go. topped out at about 30mph. That seems slower than before. 5 people on her two adults two teens and a 9 year old. Thoughts?

 

[Jiggz]

With 5 people and 30 MPH at WOT is not bad at all for an 85 HP. With 4 people onboard and 125 HP the most I can do is about 35~38 MPH!