"Right in the middle of it!!" Carb question??!?

[Dennisanoka]

Re: "Right in the middle of it!!" Carb question??!?

After the engine has been idling rough for awhile have you shut it down and inspected the plugs? Do they all look the same? Or is one much wetter/oilier than the others?

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

andy 6374:
The throttle shutters are completely closed, and synched to perfection to all open at the same time. I had done this earlier following the directions in the book and found them to be slightly off when I pulled the carbs last time. The culprit was some slight wear in the linkage that connects the two sides. Now they open evenly but it didn't help. I"ll check the choke trick but the problem seems to be more of a quick cough and pop rather than a longer sputter. The idle jets are the correct size, checked them all.

Dhadley:
Yeah, that was my thinking about the jets and especially the line about increasing horsepower. Should have seen that writing on the wall, but the guy did come highly recommended when I checked him out. After seeing some of the work he's done so far on the boat/motor I have serious reservations about his work. It was only a thought, possibly worth the $40.00 for new jets to try a different size. If you did have to re-jet it, any suggestions??

Iwonbat:
Next time I pull the carbs I'll check them out and get back to you if they're warped. Thanks!

Dennisanoka:
You know, I hadn't thought of that. They've all looked the same when I've pulled them before, but I might have been running it faster than an idle to even them out. I might run it up in the yard tomorrow and let it idle for a bit and check that out. I'm gonna bring a timing light out the next time I go to see if I can see a cylinder drop out.

Thanks for the suggestions, keep 'em coming if anything comes to mind. I'll update after looking into some of this.

Evan

 

[Dennisanoka]

Re: "Right in the middle of it!!" Carb question??!?

I won't bore you with all the details but I had a similar issue. If I ran it 3000 rpm and above then stopped and checked the plugs they were all nice and light brown and ran like a top. But if I let it idle it was rough, the lower bottom left plug #4 would foul out caused by my VRO leaking fuel back into the pulse hose. I replaced the VRO with a standard fuel pump. By the way I give all the credit to some really great helpers on this forum for nailing that one for me.
If you want to look at the thread search for threads started by me and the title: 89 90hp Rude missing on one cylynder

This may not be your problem but it's a good one to know about.

 

[Dennisanoka]

Re: "Right in the middle of it!!" Carb question??!?

BTW, the timing light won't tell you if a plug is fouling out and not firing as was the case in my situation because it will still be getting spark.

 

[Dhadley]

Re: "Right in the middle of it!!" Carb question??!?

OK, you say it coughs at idle. Does it cough back thru a carb throat or the exhaust?

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Thanks Dennisanoka, interesting thought since the oil injection is disconnected, but I don't think I'm ready to change out fuel pumps yet. Maybe later though after I've exhausted a few more options.

Dhadley, It coughs out through the exhaust then nearly stalls and picks back up again to idle. It does it sporadically, running a bit ragged (not holding an even rpm, quick surges and dropouts) but generally okay for a bit, then coughs & recovers. It does it more often under the load of being in gear vs. idling in neutral (but it will still occasionally do it an idle as well). The fact that it doesn't do it consistanly would lead me to thinking it's possibly being electrical, not fuel related.
This clear things up a bit more?

Thanks

 

[Walker]

Re: "Right in the middle of it!!" Carb question??!?

BTW, the timing light won't tell you if a plug is fouling out and not firing as was the case in my situation because it will still be getting spark.

An inductive timing light will tell you if there is spark at the plug or not. If there is no spark the light won't flash.
Have you checked idle timing and your recirculation valves like I suggested earlier?

 

[Dhadley]

Re: "Right in the middle of it!!" Carb question??!?

Ok, it coughs thru the exhaust. Look at each carb body and you'll see there's a plate on the side with 2 screws on each one. Take something like Engine Tune or Sea Foam and carefully spray around each one. Don't use gas. Those plates are famous for leaking. Once you find the one that's sucking air you can remove the plate and flip it over. That and a new gasket will usually correct it, if that's what it is.

Another way to find it is to pull 1 plug wire at a time while it's ideling. When it quits popping that's the cylinder that's being affected. Rember that on these motors the port carbs feed the starboard bank & vise versa.

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Thanks guys,

Walker:
No, I haven't checked either yet. I was thinking it had to be in the water to check the idle timing and I haven't had the chance to get it to the ramp. As for the recirc. valves, I was trying to figure it out from the Seloc manual today but it's not making sense. I found the four valves but would appreciate it if you could tell me the best way of testing them. The book seems confusing on which way the check valve works (push/pull syringe) and also whether or not I should be squirting alcohol into the hose into the cylinder. I'll run the tests tomorrow when I know and maybe be able to get it to the ramp for the idle timing. For that matter, just to confirm I understand that process, #1 cyl. is top starboard, and it should be in the water, in neutral, and adjust the idle screw to 18deg BTDC as needed. Anything I'm missing? Should I rev it up and check the timing at high speed? I'll have to check the book for that timing value.

Dhadley, I'll check the side covers and carb base when I'm there. Thanks!!!

 

[Walker]

Re: "Right in the middle of it!!" Carb question??!?

You can set the idle timing while running on muffs. Idle timing is 8 degrees ATDC, maximum advance is 18 BTDC.
The recirculation valves only allow flow one direction, towards the cylinders Push/pull a syringe of alcohol like they suggest is a good test.
Test the fittings at each cylinder. Alcohol should move freely both ways, in and out. Test the check valves, alcohol should not go in and air or fuel should come out when you pull on the syringe. There is also a oneway inline valve in the hose on the bottom that neeeds testiong.

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Thanks Walker! That was just what I needed for the valves. One question though, if the fitting into the cylinder is plugged, is that a straight fitting that I can poke through or do I need to be more delicate.

Thanks for the heads up on the timing. That will make things a bit easier tomorrow. I'm curious to see where the idle speed falls if the timing is correct. If I want to check the advanced timing, should it then be in neutral in the water running @ 4500-5000 rpm (I think I remember reading that in a different thread).

This all should keep me busy tomorrow!

Thanks again

 

[Walker]

Re: "Right in the middle of it!!" Carb question??!?

Yes you can stick a wire or something thru the fitting at the cylinders. They should be open.
Unless the linkage and screw stop has been messed with then your WOT timing shouldn't be messed up.

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Unfortunately Walker, both the linkage and the screw stop have been messed with. That's my other project today, shifter linkage. The shift linkage has always been right at the end of it's adjustment and shifting hard. I changed cables which helped it shift better but it's still at the same end of adjustment. I pulled the lower end off yesterday to check it out and it appears that the "mechanic" who did the rebuild didn't pay much attention to shift rod height when he re-installed it. It was off almost a 1/4". I brought it back to book specs, and hopefully it will put that shift linkage where it should be (and also get rid of the "bump" that just started last week...."). Given that, any advice on checking/setting the advance timing??

Evan

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

AHHHAAAA! Good call Walker! The four recirc valves tested good but the check valve underneath flows both ways. I'm off to find one and throw it back together to set the timing. I'll let you know the outcome.

Evan

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Update:

I didn't end up having a bad check valve after all, just didn't understand that the check valve was on only the small hose and not the whole fitting. I did set the shift rod to the proper height and put the lower end back on. The adjuster is right in the middle where it should be and the "bump" is gone, thankfully. I did also find the cause of the stiff shifting that came with the boat. It seems that the tube through the midsection that the shift rod goes through and the hole in the base that the lower section attaches to don't line up well, which was causing the shift arm to rub on the side of the tube (actually wore an oval into the tube). It looks like the rubber shock mounts under the two side covers in the midsection that attach the motor mount base to the midsection are old and dry-rotted. It seems that they might have swelled or stretched to the point that it's moved the tube out of place. I cleaned the tube and rod up a bit and greased them and it shifts much easier now. Unfortunately, it still doesn't run any better at an idle. I did set the low end timing which got the idle speed where it should be but it still seems to drop a cylinder or cough a bit. It occasionally runs very well for several minutes at a time, then it starts to cut out. I'm leaning towards an electrical issue now, it wouldn't run so well for as long as it does if it was a straight fuel issue. Soooooo, it's off to do more research through the forum and I'll post a new thread with more questions or conclusions.

Thanks Walker and Dhadley and everyone else for all the input!

 

[Dhadley]

Re: "Right in the middle of it!!" Carb question??!?

The lower mounts get corrosion built up behind them and that's what causes the shift shaft psaage to get out of line. New mounts will let it all line up again.

As for the idle, don't be too sure it's an electrical issue.......

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

Thanks for the confirmation of the lower mounts Dhadley. I haven't ruled out either system yet, but I'm digging a bit more on the electical. I pulled the flywheel to look for possible worn wires/shorts coming off the stator or timer base and it mostly looked pretty good. There is some corrosion on the flywheel magnets and the same and what looks like black paint on the stator magnets that I'll clean off. I removed the stator to look at the timer base it appeared to be in decent shape except for a small hole in the side (@ 1/8"x1/4") that I can see rusted/corroded metal windings inside. I'd like to think this might be THE problem but it is at least a problem. It does run very smooth off idle and I would think it would be more consistant of a problem rather than the intermittant issue I have. Any thoughts on repairing it, possibly a little liquid electrical tape?? Or does it need to be replaced?

Evan

 

[Mickyfinn]

Re: "Right in the middle of it!!" Carb question??!?

I'm gonna move this to a new thread......