68 500 slow, dies after while, clattering

[tredragon]

Long story, so I'll get to the point:

On the way back in, we still only could pull off 10mph (see second post) and then, the engine would just die after a few minutes and I'd re-start it and it would run at WOT for a few more minutes. That's how we limped home. All the while with me turning the screws to see if I could help matters, the battery was almost dead (I had to pull start it twice so the stators had just given it enough juice to start itself, barely)

The closer it got to dying, I noticed a clattering sound. I also noticed that the bottom idle mix screw didn't seem to affect the motor's "happiness" nearly as much as the top's. The bulb didn't seem incredibly hard either though.... although continually pumping it didn't seem to make it run any better.

We limped home with the last stretch being our best... we made it at WOT (10mph) for about 7 or 8 minutes straight... took us about 6 or 7 die-restart's to get back. Idle is rough, I can lean out the mix and make it idle better but then it stalls under load and won't throttle up. Again, the idle speed is turned all the way "up". If I had to guess? one or more cylinder aint doin much. Either because it's not getting fuel (clattering=detonation?) or it's down for another reason.

Ideas?

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

(This is the long version prior to the above)
So here's my Saturday (yesterday):

My tube came in early on Friday so I'm excited that the whole family can finally have a nice day on the water rather than watching me fish or my youngest (2) having nothing to do. We plan to hit up a sandbar about a mile up from the launch.

We idle out of the creek and then I open it up all the way... We're doing 10mph... mind you I have consistently been around 22-23mph in this boat. I put up with the slow speed only for a few minutes. At this rate it's going to take us forever to go 1 mile.

I pulled the cover and figure... last time it did this (which was once) I richened up the mix a little and was back up to top speed. So I gave 1/4-1/2 turn on both idle mix screws and fired her back up... still 10mph.

After a series of tuning the carbs (eventually it wouldn't idle, the idle stop is screwed all the way in... meaning, can't idle any faster).... my steering cable broke and the motor wasn't running any better. I ran back and grabbed one side of the cable by hand and sat in the back seat for 20 minutes while we putted along to the sandbar. My wife and kids jumped out and swam further in. I fixed the steering and then attended to the motor.

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

pics of plugs in order, 1,2,3,4 left to right... plug 4 aint lookin so hot.

Cause or effect?

.

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

Also, note idle stop as mentioned

.

 

[BigWake]

Re: 68 500 slow, dies after while, clattering

have you tryed putting new plugs in it?Also try cleaning the carbs....You need to do a compression test make sure all 4 cylinders are with in 10% of each other and over 100 psi or real close to it.

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

the problem is that i can't really test it for sure without another hour's drive to the lake. I can throttle it up to WOT (did on the lake yesterday) and it would run like a top at high RPM's. Just under load at WOT it wasn't running at peak capacity and eventually would just die after a few minutes.

I guess I need to know if the plugs were part of the cause, or the effect... I don't want to put plugs in it only to foul them up again...

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

bump, waiting for JP, Ed, Laddies, or one of the rest of you salts to give me the best order to attack this. wife wants to sell the boat for something else at this point.

 

[BigWake]

Re: 68 500 slow, dies after while, clattering

plugs are cheap put some plugs in it...

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

did. actually, walmart was only place open and believe it or not.... they had a 76V just like what I pulled out of #4 cyl. (that was the one where the electrode was completely shot). I was able to pull start it (because either something wonky is going on electrically or the battery is just bone dead... or the starter died, including solenoid... no clicking, no noise, no solenoid, nothing but lights turn on, elec. choke works fine...)

Anyways it ran but still having issues where tuning idle mix on bottom carb doesn't seem to affect motor much at all while top carb seems to make a difference with every 1/8 turn. Still not sure I'm hitting on all cyl. Going to try and rent a comp. tester from the local auto parts store tomorrow.

Oh, and I verified I'm getting fuel pumping from the bulb to the fuel pump... I'm actually kinda hoping that it's the fuel pump or one of the hoses that goes to a carb...

Still soliciting more ideas though! ;-)

 

[This_lil_fishy]

Re: 68 500 slow, dies after while, clattering

I'm gonna say you need to pull the carbs and rebuild them. Plug one looked okay, but they seem to get worse down the line all the way to 4 which is completely shot. You've likely messed up the idle screws and fouled the plugs, and now everything is outta wack.


Ian

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

that would make sense I guess. I had the mix screws set pretty good (going by emckelvy's recommendations) by turning them into seat, then backing out about 2 turns, then tuning for max idle plus 1/4 or so, then tuning according to hole shot response.


Then when I had issues with WOT performance, I didn't know any better and just kept playing with idle mix, pumping bulb... figuring it was a lack of fuel problem. I probably threw the mix so far out of whack that I fouled the plugs, which led to it clattering and missing so badly. I guess it's time to study up on carb rebuilding.

Can anyone recommend a particular kit that seems to have everything one would need and nothing else? Or maybe there really aren't that many choices... this is my first time looking into this.

 

[tredragon]

Re: 68 500 slow, dies after while, clattering

Oh, and I probably should just replace the fuel lines that look pretty cracked (at least from water/fuel separator to engine, and to fuel pump) Does it make sense to reubild the fuel pump while i'm in there?

 

[This_lil_fishy]

Re: 68 500 slow, dies after while, clattering

That's likley the root of the problem. You likely will find the bottom of the carb bowls full of black 'powder' like stuff. This stuff is actually the inside of your fuel lines and other rubber components. So here is my order of attack:

1, Replace all fuel lines.
2, Rebuild fuel pump (the parts are cheap, so even if it is working do it anyhow)
3, Rebuild carbs (they are simple, but the kits can be pricey)
4, Replace plugs
5, Adjust carbs on muffs
6, Adjust carbs on water

Try and find the original idle stop locations, as for re-adjusting the idle/spark stops ask others....I dunno. I didn't need to mess with mine.

Ian

 

[emckelvy]

Re: 68 500 slow, dies after while, clattering

Didya replace ALL the spark plugs while you were at it? All them plugs seen better days, notwithstanding #4 which was totally fried!

If you didn't replace the others, it's gonna run like you-know-what.

If you're seeing a lot of trash in your fuel system, it might be time to renew a few things as suggested. Seeing as how you had 'er running pretty good, something adverse has happened.

I'd make sure the fuel lines etc are up to snuff. You could try a quick 'n' dirty on the carbs and see what happens (take the idle needles out, blast the passages with carb cleaner then compressed air; remove the brass main jet plugs, one at the bottom front of each carb, and pump clean fuel thru the carbs via primer bulb/hose).

If the Quick 'n' Dirty don't improve things (sometimes it does, so it's worth a shot!), time for more 'intensive care'. Pick up a couple of "carb packing kits" and maybe consider new needles/seats and floats. Might as well Get er All Dun once you're in there!

And BTW, a compression check certainly won't hurt things, if you have a gage handy. If not, 'rope' it over by hand and feel each compression stroke. Do it a number of times and you'll be able to tell if one cylinder feels 'flat'. Every compression stroke should be a nice solid 'bump'.

Have Fun!............ed