Force 125hp fouling rich?

[jerryjerry05]

If the top doesn't respond to the adjustment?
Sucking air somewhere.
You pinch off the equalizer tube between the carbs?

Do the starting fluid spray test?

 

[redfury]

I'm going to do some testing for other leaks. Obviously something is going on. I sprayed cleaner through the updraft pipe from the fuel bowl and got the pipe bent in and touching like the book says. That seemed to help some. These carbs seem sooooo simple, I can't see why the carb could be the problem other than the float leaking fuel into the engine, which doesn't seem to be the case. It's frustrating because I've replaced every gasket short of the case halves and the exhaust plate.

 

[jerryjerry05]

The first post you said there was a backfire that blew the bellows apart.
If it was that violent, it could have blown the seal at the top or bottom of the crank.
Also between the cyl. on the crank. Called a crank case seal F316579 thin metal ring that seals between the
cylinders. It could be broken? maybe, maybe not??

Do the starting fluid test again. Small shot of SF under the flywheel, around the base etc.

 

[redfury]

Back from my trip from Colorado, was going to work on testing with SF and realized I left my gauge panel switch on..dead battery. So, it's charging back up for now. I'm going to spray under the flywheel and see if it changes anything. I was thinking of switching carb positions just to rule that out if I don't get anywhere spraying. I can't imagine I'd have a fouled carb. They've been cleaned twice. I had thought that maybe there was some kind of blockage that was preventing fuel from running through the idle circuit of the upper carb, which is why I pulled it to check to see if there might be a problem, but I can easily send pressurized cleaner through the orifice both ways, so I can't imagine that is a problem. The other thing is, it doesn't run right with an open throttle properly when it starts acting up, which should remove the idle circuit from the equation. When I had the flywheel off, I didn't notice any evidence of oil around the upper crank seal. I suppose short of pulling the motor off completely, there's no way to pressure test the block. I thought about doing a leak down test, but I don't see where that would show me much.

For now, I'll just get the battery charged and see where a spray test leads me.

 

[redfury]

Shot some video

 

[jerryjerry05]

(I can't imagine I'd have a fouled carb. They've been cleaned twice. I had thought that maybe there was some kind of blockage)
A piece of dirt the size of a pin point can screw with you.
Working on a 92 120, cleaned the carb 3 times and had the same problem, 4th time did the trick.

Video: that really sounds like it's sucking air somewhere?? or the timings off.

. (When I had the flywheel off, I didn't notice any evidence of oil around the upper crank seal.)
You probably wouldn't see oil at the top, it sucking air not pushing air out.

Leak down test, wouldn't show much.

Try the carb swap, do it on a warm motor or starting cold might be a problem.​

 

[redfury]

[h=2]So, out at the boat today, managed to get it running really nice on muffs, but then noticed the timing screw had come out of the timing block ( I was doing a little bit of timing by ear to see if I could clean up the misfiring, which it did...it was sounding glorious ).[/h] Anyone have the measurement between the timing block and the timing tower arm so I can reset the timing...I really don't want to guess and end up with a backfire that might do damage. If not, I'll have to pull out my spark plug grounding block and pull the plugs and check it that way, but I don't know how far in the screw needs to be...

 

[Nordin]

You have to set the timing with a timing light nothing else will be correct.
Set the timing 28dgr BTDC at WOT and cranking speed or if you have an assistant 30dgr BTDC at WOT in lake.
There are 4 marks at the flywheel. From left to right 32 dgr BTDC, 30 dgr and 28 dgr and at the right a single mark that is 0 dgr.

You can check out the sticky at the top of this forum by Frank A how to do the timing.

 

[jerryjerry05]

Yup no tune by ear with any motor.
Read ALL 4 top posts.
Lots of good info there,

 

[redfury]

Yup, that's what I did. Amazingly, I had rethreaded the screw in at 30 degrees. I pulled the plugs and shorted the coils to ground with my grounded L bracket which works really well for this and set the timing at 28. Having a remote starting cable makes this job so much easier. Totally worth the tool investment.

So, I went through everything again. Got a crisp snap throttle, she sounds like she's purring along pretty good. Put the cowl back on and it sounds like the engine is being choked. ( there's no insulation material left in the cowl, so there's no air restriction other than the inlet on the top. I had done most of my tuning with the carb hats off as well. I'm going to give it another check down on the entire carb/timing sync list and then get it on the water for some hole shot tuning.

 

[jerryjerry05]

If you choke out with the cover on???
Then the rubber boot for the exhaust might be split? look on the bottom?
Or there's a leak where the adaptor plate meets the block.
I had a leak there and covered it with silicone (for a quick fix) worked so well I never did finish the job.

 

[redfury]

I should check it, but it's almost brand new. By choking out, I meant that it ran differently with the hood on. Other than the boot, is there a good way to check the plate gasket? The thing is, the first time on the water, I ran it solid for at least 30 minutes without any issues... I thought I had gotten it licked. The second time out was when I was having problems again where it seemed like it was lugging down like it dropped a cylinder. While I was checking the timing, we had a burst of power like a cylinder had come to life briefly, but I had checked with the timing light and had a signal from each of the cylinders. I wish I could log the spark of each of the cylinders while it was running but I don't have a 4 channel scope.

 

[redfury]

Any chance this part is still available?

 

[jerryjerry05]

Yes
F499035 $8
They might have it on this site?

 

[redfury]

I have it on order. In the mean time, the boat sat for a couple of days. Turned on the water, with the cowl on, it started almost immediately and then died. Started right up and sputtered a bit and stayed running...no choke, no priming the bulb...so I think the fuel system is in good shape. I'm going to bring the boat to the lake and do the full link/sync/idle speed/carb adjustment on the lake. Once I get the part, I'll have to redo the timing anyway...at least the rest of it will be where it needs to be. If I have problems beyond that, my seasons done for. I may just pull the engine and rebuild it...the pinging noise that I hear after giving it a little bit of throttle really has me unnerved. I don't want to damage pistons/cylinder walls just because I'm stubborn and want to use the boat.

 

[jerryjerry05]

When you pull the old part??
Measure how long the threads are sticking out of the old part.
That should help getting the timing back to where it should be.

There should be a jam nut on the screw to lock it in place.
It's 1/4-28 nut. F2015 part#
But any stainless nut that size will work.

 

[redfury]

I have the jam nut, I took a picture of it originally to see where I had it set at when I originally set the timing so I could replicate it. I'm going to the lake today for sure, though I don't know for how long, the weather looks crummy. I'll report back when I'm done for the day. Hopefully good news, but I'm not holding my breath ( I still think there's something more sinister going on...just my gut feeling ).

 

[redfury]

So, looking back at an original video of the motor running, I can hear a similar sound coming from it, so I'm not overly concerned. It ran well in the water. Tuning the carbs helped a bunch, as did doing hole shot runs. I ran it pretty good and don't have the problems that I used to. It still feels like there's something a little off though. It feels like during lower rpm operation like the bottom of the boat is dragging on something briefly, almost every as if there was a small peak of a sand bar hitting the hull and causing it to slow down. I'm not sure what to think about it. I'm sure getting the timing screw base replaced will help stabilize the timing, so I won't fret about it too much until I can get that replaced. No evidence of overheating, and it doesn't smell like an over rich condition anymore. I need to get a 17P prop for it though...

 

[jerryjerry05]

Other than the false start it looked good.
Yes change the prop.
Idle about750-800 might help the holeshot too.

 

[redfury]

Still has a difference when the cover is on vs off, but it ran pretty good the whole time I was out...it restarted hot fine, started cold fine. I ran the trolling motor a lot, so the motor had a good chance to cool down. I definitely need a 17p prop. I have a 15 and a 21P. I might throw the 15p on and watch the rpm just to see where I am with it...but I've thought a 17P would be right for it...