About to throw in the towel.. I only have WOT and idle..

[erikpn]

Ready to give up on this 87 force 35. Changed the fuel pump diaphragm (the old one was fine), cleaned/adjusted the carb, getting spark, getting good compression. But I don't have a midrange, the motor runs fine at wot and fine at idle. Put the throttle anywhere in the middle, and the motor will start to wind up, then violently shake and drop rpms, over and over. Like an extremely bad misfire. After I replaced plugs, it seemed to run better. After I adjusted carb it ran better. But eventually it returns to running like before.

Some of the wires from the stator look heat damaged. Looks like the battery shorted them once. I wrapped any spots where patches of bare wire was with insulation. Should I pull the stator? Could something like that cause misfiring only at mid throttle? That flywheel nut is an absolute beast to remove though..

 

[Smokepole27]

Re: About to throw in the towel.. I only have WOT and idle..

Check for air leaks sounds like when you fuel pump is starting to draw fuel air is getting in their somewhere and not alowing the proper amount of fuel. Check quick disconnect fitting for bad seals, cracked fuel line that you may not see. But I would suggest air. Ive found 80 percent of issues with running is due to fuel related issues. Or even the valves might be sticking on your fuel pump if you have those on there.

 

[john from md]

Re: About to throw in the towel.. I only have WOT and idle..

Sounds like you are running lean in the midrange. How many turns do you have your idle mixture screws set at?

John

 

[erikpn]

Re: About to throw in the towel.. I only have WOT and idle..

It's about 3/4 of a turn out from bottom. If I turn it another 1/4 turn in, motor starts sneezing. If I turn it 1/4 turn out, motor rpms drop and it starts to die.

I see a deal on a Yamaha 70hp, it's a 1992 with power tilt and trim, controls nd tach included and looks in excellent condition for an asking price of $850. I would jump on it if I wasn't leaving in 4 weeks anyways.

 

[john from md]

Re: About to throw in the towel.. I only have WOT and idle..

Open them up 1/2 turn to 11/4 and run it and see if it runs better. Your idle may be rough but live with it until you see how it runs.

Let me know the results.

John

 

[droach77]

Re: About to throw in the towel.. I only have WOT and idle..

Mine is doing the same thing, my fuel line jumps when it coughs and puffs smoke somewhere around the fuel pump, is yours doing the same thing?

dave

 

[john from md]

Re: About to throw in the towel.. I only have WOT and idle..

Dave,

The fuel pump is driven by compression and vacuum in the number 2 and 3 cylinders. When you remove the pump, you will see a hole in each chamber. These go to the respective cylinders.

If an engine backfires through the intake, it can force smoke through the pump gasket. It can also damage the pump diaphram. That is why you should always re-examine a fuel pump diaphram periodically while troubleshooting an engine. You could put a new one in on one day and, after the engine backfires a few times, it could have a tear in it the next day.

John

 

[erikpn]

Re: About to throw in the towel.. I only have WOT and idle..

Open them up 1/2 turn to 11/4 and run it and see if it runs better. Your idle may be rough but live with it until you see how it runs.

Let me know the results.

John

It's still doing the stutter/shake at mid throttle after adjusting it. These motors are not suppose to have adjustable timing, but you can adjust the throttle independently of the position of the trigger housing. I just adjusted it so that the full throttle stop is all the way back against the engine block while the WOT mark on the throttle cam is on the throttle valve of the carb. Could that be related to it? There's no timing marks on the flywheel, maybe this rough form of adjustment is causing bad preignition? I would buy that yamaha but I'll hardly get enough use out of it to justify it.

 

[CharlieB]

Re: About to throw in the towel.. I only have WOT and idle..

You need to get a factory service manual and follow the directions to set WOT ignition timing, THEN set the throttle/carb linkage to the lever.

Timing is advanced as the throttle opens, too advanced and midrange can be affected, too advanced can destroy (melt) pistons.

These are NOT settings to be messed with, follow the directions.

Carb float height adjustment can also contribute to strange engine operation as a lower float can also cause a lean condition.

 

[erikpn]

Re: About to throw in the towel.. I only have WOT and idle..

You need to get a factory service manual and follow the directions to set WOT ignition timing, THEN set the throttle/carb linkage to the lever.

Timing is advanced as the throttle opens, too advanced and midrange can be affected, too advanced can destroy (melt) pistons.

These are NOT settings to be messed with, follow the directions.

Carb float height adjustment can also contribute to strange engine operation as a lower float can also cause a lean condition.

There are no directions for ignition timing. The manual has one sentence on timing that says that the ignition timing is not adjustable on this model, and that is that.

If anything, the engine appears to be running too cool. The thermostat wasn't there when I checked, and the spark plugs get fouled quickly. I am using a 50:1 gas/oil ratio, which I believe is correct.

 

[john from md]

Re: About to throw in the towel.. I only have WOT and idle..

While the timing is not adjustable on the 35hp engine, the carb and linkage adjustments are. If they are not adjusted correctly, you will get more or less spark per a given throttle plate opening. It is critical to adjust the linkage properly on these manual spark advance engines.

As for the thermostat, the engine will run fine without it. It will use more fuel because it is not at its optimum running temp but you won't notice any performance problems.

John

 

[Smokepole27]

Re: About to throw in the towel.. I only have WOT and idle..

Have you did any readjusting to the idle? If so then make sure to adjust it with the air fuel mix, it worked for me on my 30 mariner. Ever once in a while shell start messing up on me on top end and when you floor the throttle, that just tells me its time to clean the carb again and start over with the adjustments.
No matter how much I try to keep it clean under the cal, crap always builds up and all it takes is for me to hit a small snag and something gets sucked up! Hope all works for you

Ryan

 

[CharlieB]

Re: About to throw in the towel.. I only have WOT and idle..

There are no directions for ignition timing. The manual has one sentence on timing that says that the ignition timing is not adjustable on this model, and that is that.

I don't know what manual you are referring to, but.....

http://web.ebscohost.com/serrc/pdf?...e475-4e0e-4db2-8023-a1f0837ffbfb@sessionmgr11

Pay attention to

Ignition Timing found on page 4

and Carb linkage found on page 2

Edit: Sorry, I mis-read your engine and I looked up the 85 HP, forget all the above. I'm still searching.

Re-edit: Only manual I know of on-line is Clymers

http://web.ebscohost.com/serrc/pdf?...e475-4e0e-4db2-8023-a1f0837ffbfb@sessionmgr11

See page 2 Speed Control Linkage

It makes reference to Ignition Timing section, but curiously that section is left out of Clymers edition, maybe they didn't want to get sued for coying too much of the Force Factory Manual???????

Read the procedure for the 85 HP originally posted above and see how close that is to the adjustments found on your 35.

Re-Re-Edit:

Oh cr@9, I just tried my links and got the same page on both,

You will have to start here

http://www.hibbing.mn.us/index.asp?Type=B_BASIC&SEC={8B2E6CEF-5E42-4BA4-AA26-31E0490E23F4}

Then click on the link to Boats then again on Force, etc.

Then check out the timing for the 85 and see how it is done then go look at your 35 again to see the WOT Timing stop and the single line scribed on the flywheel.

 

[erikpn]

Re: About to throw in the towel.. I only have WOT and idle..

There's no marks on the flywheel though. None at all.

 

[CharlieB]

Re: About to throw in the towel.. I only have WOT and idle..

Electric start?

Sometimes they hide a small line on the top side of a ring gear tooth.

Remove the spark plug, bar the motor over by hand, use a piece of stiff wire or small screwdriver to feel the piston, stop turning when the top cyl is at Top Dead Center.

Look on the intake side of the motor on top of the ring gear a couple of inches each side of center to see if one or two of the ring gear teeth have a punch mark, an X, or a line.

The first should be max timing, the last should be TDC.

 

[john from md]

Re: About to throw in the towel.. I only have WOT and idle..

Remove the throttle rod from the trottle cam and manually rotate the cam to contact the throttle pickup roller. Adjust the trottle cam pick up point by loosening the nut on the eccentric cam on the throttle pick up roller and rotating it until it contacts the cam at the pickup mark. Retighten eccentric cam lock nut. Reattach the throttle rod and move the throttle to the WOT postion. Look down the carburetor bore and make certain the trottle plate is open all the way. If the throttle plate is not in the proper position, adjust the length of the throttle rod until the correct result is achieved.

This is about all you can do with this engine.

John

 

[jjzepplin]

Re: About to throw in the towel.. I only have WOT and idle..

You may be just banging your head for no reason at all. Did you say your stator was burnt or damaged in some way? I had a 115 merc completely rebuilt at a reputable shop . Idled great and sounded good on the muffs. I took her out time and again and thought I was having fuel delivery issues because she would go great for fifty feet and begin to stumble and chug etc. Messed with it for a month and wanted to get my money back for the rebuild and finally got a second opinion. STATOR !!!! to put it short. All the new pistons and carb work is useless if your stator is damaged !!!!! I replaced the stator (myself) and that motor was sooooo good to me that I hate to have ever sold it. A lot of the force engines seem to have had stator problems. I was going to get a small jet boat that had a merc engine built on the force type head and found that there were stator problems with that engine too. Had to look for the red stator not the black on as the black one was not good. The one I put on my engine was black but it was genuine mercury and I had no problems after that. I think it was about $100.00. Hope my solution helps.

 

[erikpn]

Re: About to throw in the towel.. I only have WOT and idle..

Remove the throttle rod from the trottle cam and manually rotate the cam to contact the throttle pickup roller. Adjust the trottle cam pick up point by loosening the nut on the eccentric cam on the throttle pick up roller and rotating it until it contacts the cam at the pickup mark. Retighten eccentric cam lock nut. Reattach the throttle rod and move the throttle to the WOT postion. Look down the carburetor bore and make certain the trottle plate is open all the way. If the throttle plate is not in the proper position, adjust the length of the throttle rod until the correct result is achieved.

This is about all you can do with this engine.

John

Yep, thats what I did already. I now think its a carburetor issue with the needle valve. I adjusted the float so that it was parallel when upside down, and lost WOT. Readjusted it so that the float was significantly past parallel, and it became much easier to blow through the fuel inlet and regained WOT. midrange also improved, but theres still surging/stumbling. The dead zone is smaller though. I am going to replace the needle valve assembly and see if that helps. The carburetor bowl has a dent in it too, hammering it out might help a bit..

 

[Smokepole27]

Re: About to throw in the towel.. I only have WOT and idle..

Ummm not if its cast aluminum, not to sure what they are made of but be careful u might break it.