85 evinrude 90 will not plane out.

Hi everyone, I just bought a monark bass boat with a 1985 evinrude 90 horse. I took it out the first time and ran a 6 gallon tank of 50:1 mixture and it ran great minus a couple stalls after running it hard and trying to idle, next day I took it out and ran fine for a while then it lost power and would barely plane out. On land it seems to run fine but when I put it in the water it does not have full power under a load. I looked at the plugs and they looked a little oily so I cleaned and wire brushed them until they looked like new. same problem after that. I took the carbs apart and they were spotless so I cleaned them anyway and put them back on. I also tested spark and compression on all cylinders. good spark and 125 to 135 psi on compression. I noticed a couple of fuse blocks on the top rear of the motor and a couple electronic components that I have no idea what they are or if they could be causing the problem. I appreciate any help or points in the right direction! Thanks.

Tom

Re: 85 evinrude 90 will not plane out.

When a boat runs fine one day and not the next day, it usually is a spark issue. Your engine will seem run fine on the trailer on 2 or 3 cyls-it's really hard to tell. You need all 4 firing when it is floating in the water. Start your engine on the trailer. Check for spark two ways: 1. with an inductive timing light, check spark on each plugwire. The flashes from the gun will tell you about the quality of spark:misfires, no fires, weak firing. 2. When you have it running on the trailer, use a set of insulated pliers and pull one of the spark plug leads off one spark plug. The engine rpm's should drop. Put that plug wire back on, pull another wire off plug #2. The rpm's should drop. Etc, etc. If you get no rpm drop on one plug likely it may not be firing. Remember, weak ignition components tend to fail once the engine warms up to normal operating temps. Make sure the engine is fully warmed up when you try your spark checks. That engine has two identical power packs. They can be swapped for ignition testing purposes.

Re: 85 evinrude 90 will not plane out.

All it takes to make your engine run properly is timed spark, fuel and compression.
It sounds like your compression is OK. When you checked the spark did you use an air gap tester set to 7/16"?
When you cleaned the carbs did you remove and clean the high speed orifices?

Re: 85 evinrude 90 will not plane out.

emdsapmgr said:

When a boat runs fine one day and not the next day, it usually is a spark issue. Your engine will seem run fine on the trailer on 2 or 3 cyls-it's really hard to tell. You need all 4 firing when it is floating in the water. Start your engine on the trailer. Check for spark two ways: 1. with an inductive timing light, check spark on each plugwire. The flashes from the gun will tell you about the quality of spark:misfires, no fires, weak firing. 2. When you have it running on the trailer, use a set of insulated pliers and pull one of the spark plug leads off one spark plug. The engine rpm's should drop. Put that plug wire back on, pull another wire off plug #2. The rpm's should drop. Etc, etc. If you get no rpm drop on one plug likely it may not be firing. Remember, weak ignition components tend to fail once the engine warms up to normal operating temps. Make sure the engine is fully warmed up when you try your spark checks. That engine has two identical power packs. They can be swapped for ignition testing purposes.

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I don't have a timing light at the moment but when I pull the plugs one at a time the rpms drop on each cylinder. Also the engine seems to be running rough today. I also noticed that one head gets hotter than the other. One I can rest my hand on and leave it there.

Re: 85 evinrude 90 will not plane out.

emdsapmgr said:

When a boat runs fine one day and not the next day, it usually is a spark issue. Your engine will seem run fine on the trailer on 2 or 3 cyls-it's really hard to tell. You need all 4 firing when it is floating in the water. Start your engine on the trailer. Check for spark two ways: 1. with an inductive timing light, check spark on each plugwire. The flashes from the gun will tell you about the quality of spark:misfires, no fires, weak firing. 2. When you have it running on the trailer, use a set of insulated pliers and pull one of the spark plug leads off one spark plug. The engine rpm's should drop. Put that plug wire back on, pull another wire off plug #2. The rpm's should drop. Etc, etc. If you get no rpm drop on one plug likely it may not be firing. Remember, weak ignition components tend to fail once the engine warms up to normal operating temps. Make sure the engine is fully warmed up when you try your spark checks. That engine has two identical power packs. They can be swapped for ignition testing purposes.

Click to expand...

I was hoping that it didn't lose rpms on one side so I could try swapping the power packs, wasn't that lucky. thanks for the reply!

Re: 85 evinrude 90 will not plane out.

That engine has two thermostats, one for each head. It is possible to overheat one head and not the other. You may want to pull the thermostat housing apart and repl both stats. While you are in there, inspect the pressure relief valves.

Re: 85 evinrude 90 will not plane out.

emdsapmgr said:

That engine has two thermostats, one for each head. It is possible to overheat one head and not the other. You may want to pull the thermostat housing apart and repl both stats. While you are in there, inspect the pressure relief valves.

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Thanks, I now found brown liquid on the plugs from the head that stays cooler. Believe it is water. I don't even see where the t stats are located and I'm trying to locate it. I'm hoping this doesn't mean I have a blown head gasket but atleast if it is, I located the problem and can fix it. Also, the plate on the back of the engine has water leaking from the gasket and bolts. I'm not sure what is behind that plate either.

Re: 85 evinrude 90 will not plane out.

side-wayz said:

Thanks, I now found brown liquid on the plugs from the head that stays cooler. Believe it is water. I don't even see where the t stats are located and I'm trying to locate it. I'm hoping this doesn't mean I have a blown head gasket but atleast if it is, I located the problem and can fix it. Also, the plate on the back of the engine has water leaking from the gasket and bolts. I'm not sure what is behind that plate either.

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Would I still have good compression if the headgasket is leaking?

Re: 85 evinrude 90 will not plane out.

Here are yout thermostats, #78.
http://www.ishopmarine.com/ishop/js...nown&isFrPG=false&forItemCode=&pCode=C0217333
It is possiable to have a head gasket leak water and still have good compression.