Odd ignition problem..only three cylinders firing

[Silvertip]

Re: Odd ignition problem..only three cylinders firing

So why aren't we getting answers to the following questions:
1) Did you acquire the boat this way?
2) Did you own this boat and the problem just occured.
3) If the answer to #2 is yes, what were you doing when the problem popped up?
4) Can you tell a good running motor from a bad one?
5) Did you attempt to add or change something? or more importantly
6) Are you just screwing with us? If you are, we have better things to do.

 

[Gary H NC]

Re: Odd ignition problem..only three cylinders firing

Test each plug wire the old fashioned way..stick a finger in the boot with the motor running.

When i was a kid i would see my dad and his drinking buddy do that..If they looked like they were having a seizure then that cylinder is getting good spark...lol!

Just joking..do not try that....

 

[bchoate]

Re: Odd ignition problem..only three cylinders firing

This is simply rediculous. Under the circumstances described, this is a boat with two very poorly running engines and to have both of them exhibiting the same exact issue is simply unreasonable. I personally doubt either engine would actually run with half its cylinders disabled. And I find it odd that one could not determine that the engines are or are not running properly since loss of three cylinders would produce very poor idle quality. Further, either engine should run on five cylinders so pulling one plug at a time should not kill the engine. In fact, one can actually cross two plug wires (plug wires on wrong cylinders) and the engine may idle reasonably well depending on which two wires were crossed. So either we have two engines that are running normally and the testing is flawed, or we have two engines that have absolutely zero compression or spark on the 2-4-6 side of both motors in which case both should either not run at all or run like an old John Deere. Connect a timing light to each plug wire to verify spark on every cylinder. A compression test is in order after that. It is certainly possible that both engines injested water but to have it impact 2-4-6 on both engines identically means you should probably not go to Vegas and bet a load.

#1 Mercruiser has never offered a counter rotatiing "ENGINE" with an "ALPHA DRIVE". And the firing order is clearly marked on the Thunderbolt distributors. If the engines run good, leave them alone, other than normal maintance/tune-ups ,etc.

 

[bobuk]

Re: Odd ignition problem..only three cylinders firing

Ok, i have done a compression test with all cylinders comparable on both engines. The timing light showed a spark at all plugs. I think that the firing order is 165432. I now need to get some decent plugs as the current ones are ngk and seam crap. I think in addition the HT leads are ancient. After testing the port engine seems ok, but the starboard engine, starboard side cyliners still seems to be not making a lot of difference when pulling the starboard leads compared to pulling the port side leads. I do know this sounds odd, but it could be a combination of defects on the entire engine that initially manifest it self on the starboard side possiblly due to the set up of the thnderbolt ignition???

Bob

 

[chiefalen]

Re: Odd ignition problem..only three cylinders firing

You say you have good compression, but when you pull a lead nothing happens?

Thats why your concerned. Correct?

And i posted lets see if there is a problem bye doing a vacuum test, and i posted how to do it.

If sir, you are really serious about your motor, than do the vacuum test, post the result.

If anything at all is amiss it will show up.

Until than have a nice day.

 

[Bondo]

Re: Odd ignition problem..only three cylinders firing

I do know this sounds odd, but it could be a combination of defects on the entire engine that initially manifest it self on the starboard side possiblly due to the set up of the thnderbolt ignition???

Nope,..... Not really....

I'd sooner think Plugged Carb jets or something if it Really isn't running on only 1 side of the motor....

The Induction system, Is in fact divided between the sides of the motor....
The Igntion system is Not, but random around the motor...

Chiefalan's Vacuum Test might lead you in the right direction,...
But,...
I don't think your motor has a usable vacuum port,.. Atleast not Easily usable anyways...

 

[chiefalen]

Re: Odd ignition problem..only three cylinders firing

I know theres a plug on the intake just put in a fitting that accepts the gauge fitting, really simple.

You already have the link.

Your serious about it do it.

Post the result.