1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

[jcw74801]

'96 150 Ocean Pro on Cajun Fishmaster 21' CC.

First, this engine has a cracked block. It was cracked when I bought it 3 years ago. It is not near the cylinder heads. The engine runs strong. The following symptoms did not occur during the first year that I operated the boat:

When cruising at any speed on plane I have an intermittent occurrence. Not really a vibration. Can't seem to feel it in the steering wheel or seat. I want to say flutter. I know the term is used to describe reeds but I don't know what that feels like and it's not at high rpm but all rpm's. It could also feel like 4-cycling. And it's a feeling, not a sound. There is a slight loss of thrust when it happens. It might last for 3 seconds or 30 seconds. It might stop for just a few seconds or several minutes.

I'm not sure how to figure out whether it's fuel, electronics, or even in the gear train. The prop has been overhauled and had no affect.

Plugs have been changed and look good. Link & sync is done a few times per year.

appreciate any suggestions,
John

 

[jonesg]

Re: 1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

Check for crossfiring, plug wire routing, try running without the cowl for a spell and see if it goes away.
Sometimes the plug wires ground out on the cowl latches.

With a cracked block I might just run it until it gets worse enough to track down. Can you seal the crack?

 

[jcw74801]

Re: 1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

I did seal the crack with JB Weld but it reappeared. It does seep a little oil. I need to get it welded. Are there any special precautions to take before having a block welded? Like removing electronics, coils, sensors?

I don't know the age of the plug wires and there are some pretty deep grooves worn in them in a few spots so I will replace them. They're fairly inexpensive anyway.

Are inline spark testers designed to be used with the engine running? Can you install one on each plug and take the boat for a test ride to check the spark under load on all plugs at once? Or are they just for cranking only, without the engine running?

 

[Faztbullet]

Re: 1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

The problem is likely the crack as there is no oil in block except fuel/oil mixture. If it can leak out, air can leak in and may becausing a lean miss. Where exactly is crack on block?

 

[jonesg]

Re: 1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

I did seal the crack with JB Weld but it reappeared. It does seep a little oil. I need to get it welded. Are there any special precautions to take before having a block welded? Like removing electronics, coils, sensors?

I don't know the age of the plug wires and there are some pretty deep grooves worn in them in a few spots so I will replace them. They're fairly inexpensive anyway.

Are inline spark testers designed to be used with the engine running? Can you install one on each plug and take the boat for a test ride to check the spark under load on all plugs at once? Or are they just for cranking only, without the engine running?

They might want the block stripped down completely.
Inline testers,....err... a timing light.!

 

[jcw74801]

Re: 1996 150 Ocean Pro troubleshooting flutter, 4-cycling, vibration...

Inline testers,....err... a timing light.!

I wouldn't be able to see the inline tester anyways since the heads are facing aft. With a timing light it will be easy to move from one cylinder to another and examine the spark while under way.