78 200 HP not running on all cylinders

[jack78]

I recently got a 19' Bayliner runabout with a 1978 Evinrude 200 HP. I dont know the history other than it sat for the last year or two. First thing, I cleaned the carbs, replaced fuel lines, drained the old fuel, and replaced the sparkplugs. It fired first try. Took it out and would only do 4000 RPMs 30-35 MPH WOT.

Rechecked all fuel components, looks good. Spark at all the plugs. 1,2,3 cylinders run great. 5,6 dont run, can pull the spark boot without it making a differance. 4 cylinder make a very little differance when the boot is pulled.

Compression is 90-95# 1,2,3 cylinders. 85# 4,5,6 cylinders.

There seems to be excess fuel in the exhuast and a milky soup coming out the prop. I havent worked on outboards much and would appreciate some opinions before I start pulling it apart.

 

[tashasdaddy]

Re: 78 200 HP not running on all cylinders

you have 2 power packs, one for each bank. i believe you are numbering you cylinders wrong. even number are one bank, odd the other. when you look at the spark plugs they are not directly across from each other one side is higher than the other, the high side is the odd # cylinders.

 

[jack78]

Re: 78 200 HP not running on all cylinders

Ok, then it would be 1,3,5 running good 90-95#
2,4,6 85#. 4,6 not running. 2 not running well

 

[emdsapmgr]

Re: 78 200 HP not running on all cylinders

Put an inductive timing light on each plugwire when the engine is running. This will confirm misfires or nofires. Sounds like the missing is on one side of the engine only. If so, swap the power packs from side to side and see if the missing moves with the packs. If so, get a new pack. A milky appearance can be an indication of water. Possible you have a blown head gasket or exhaust water leak. Check the plugs after running and see if any of them have the same milky appearance. That's water and will cause misfires in a cyl. When new, that engine ran considerably higher compression-in the 105-110 range. A decarb of the engine may bring the compression up-it's worth doing.

 

[jack78]

Re: 78 200 HP not running on all cylinders

Switching powerpacks didn't make a differance. I've suspected a blown head gasket. The plugs are very clean like they're getting washed out. Thanks for the help. I'll pull the head and post what I find.

 

[jack78]

Re: 78 200 HP not running on all cylinders

It was a blown head gasket. Thanks again for the help