1993 70HP Rude.. Possible to run on one cylinder?

[jvaccarino]

Evening..

Thought boat was stuck in slow mode.. further investigation: No spark at top cylinder/coil..

With the boat running, i pulled the plug on top cylinder.. no change..
Pulled the plug on Cyl. #2.. engine stalls.
Pulled the plug on Cyl. #3 - no change.

Is it possible to run on just ONE cylinder? How f'd am I???

 

[tashasdaddy]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

yes they can idle on one. especially on muffs. you need to determine if it is no spark, no fuel, or no compression. sounds like you have 2 dead.

 

[jvaccarino]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

I'll be hooking up compression tester here in a lil bit when buddy comes over with the tester..

What causes a cylinder to "die" poor cooling system??

 

[jtexas]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

I'd say you've proved it's possible. To estimate the degree to which you are f'd, do a compression test and spark test. Many things could be causing the problem, only a few of which are major.

What spark plugs are you using and how old?
What do they look like after idling? wet, dry, carbon fouled, etc.

don't run it any more than you have to for testing....if it turns out to be fuel-related, your cylinders aren't getting adequate lubrication.

a cylinder dies due to inadequate compression, inadequate spark, or inadequate fuel.

 

[jvaccarino]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

Brand new plugs.. hate to say but.. AUTOLITE plugs.. They are a little wet with oil.. they aren't carbon fouled..

 

[jvaccarino]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

lets say it is compression.... What are the MAIN causes.. valves? P. ring?

 

[JB]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

Unlikely to be compression, but take it anyway.

Most likely is ignition, second is fuel. . .pump, then carbs.

 

[jtexas]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

causes of compression loss? broke piston, sticky rings, and failed head gasket come to mind. no valves on that engine.

highly recommend switching to champion plugs at your earliest opportunity. but seems unlikely brand new autolites would cause your symptoms.

check to see if you have spark on the top & bottom......pull the plug, reattach it to the boot, hold it against the engine block and look for a spark while somebody turns the engine over (use an insulated or plastic tool).

 

[jvaccarino]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

Can I put the coil wire from the middle cylinder to another coil, plug wire to spark plug, and look to see if I am getting spark from the other coil?

 

[jtexas]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

yes.

 

[jtexas]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

pasted from the lower unit thread:

Guys... Engine has spark, 120psi compression and all 3 carbs are getting gas!!! What else would make it still run like its in slow mode?! I disco'd the temp sensor and tried to rev w/out it.. and nothing.

Carbs getting gas, not the same thing as engine getting gas. Put some premixed fuel in a spray bottle and spray into #1 & #3 carb throats with the engine running. If RPM's pick up, you'll know your carbs need rebuilding.

Spark outside the cylinder, could be too weak to fire under compression. Spark tester (couple bucks at auto parts store), set the gap for 7/16", look for a sharp blue spark while somebody turns the engine over.

Make sure your plug wires are on the correct plugs.

 

[tashasdaddy]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

look what this guy did, and all the time it was a clogged jet.

http://forums.iboats.com/showthread.php?t=238530

 

[cmuman]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

I was very happy to figure out that my issue was a clogged jet. My engine would do the same thing. I didn't have any change on the top cylinder. I had old plugs in the engine, and that partially fooled me, so I pursued spark. I found the carb rebuilding rather easy, you just need the right tools. Be careful taking the nuts off the carb studs. I spent about 20 minutes fishing one out from under my powerhead. Good luck

 

[tashasdaddy]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

we've all being fishing in the motor cowl.

 

[cmuman]

Re: 1993 70HP Rude.. Possible to run on one cylinder?

I found all my clogging behind the carb drain in the idle jet. You should be able to pull that jet without taking the carbs off.