1969 85hp starflite, low power and cutting in and out

[68glasspar]

I checked the compression and all were 110 to 120psi. I checked the points and had champion plugs in it. I have switched to ngk and that didn't help. The engine just isn't getting to full power and then after a little bit it will start cutting in and out. Its like a fuel restriction or running lean. I ordered a new fuel pump for it. Anything else to look for?
Can an old fuel quick connect let air in the system?

 

[jimmbo]

The Ignition Coil could be having issues when it gets Warm, same can happen to the Amplifier. Also. when you had the Distributor and Rotor off, to get at the Points, did you check them over for Carbon Tracks, Cracks...?
Have you checked that the Spark is good enough to jump a 5/16" gap. consistently?

 

[68glasspar]

The Ignition Coil could be having issues when it gets Warm, same can happen to the Amplifier. Also. when you had the Distributor and Rotor off, to get at the Points, did you check them over for Carbon Tracks, Cracks...?
Have you checked that the Spark is good enough to jump a 5/16" gap. consistently?

I replaced the dist. cap with a new old stock cap and wires when i had it apart. As soon as i push away from the dock and go full throttle it's not that its cutting in and out, it just fails to get to full speed( not full rpm). after a min or 2 thats when it starts cutting in and out and back to the dock. I did check the spark at cranking speed with all 4 plugs out and it was very strong.
The only other thing is this engine has a knob to adjust idle mixture. It was frozen and i had it somewhat apart to try to free it up. I wouldn't think that would affect the top end performance

 

[racerone]

Clean the carburetors-----Find / clean the high speed jets screwed into the bottom of the float bowl.----Do not run this motor , as plugged carburetors can result in major damage to the motor.

 

[jimmbo]

When you pull the Front Cover of the Air Silencer off, you will find 4 Low Speed Needles linked to that Knob.
Go over the entire Fuel System, the Carbs don't hold enough Fuel to run a Minute, even at Idle

 

[68glasspar]

When you pull the Front Cover of the Air Silencer off, you will find 4 Low Speed Needles linked to that Knob.
Go over the entire Fuel System, the Carbs don't hold enough Fuel to run a Minute, even at Idle

The fuel tank in this boat is way up in the bow! The fuel pump is original, so i ordered a new one and will try it out. I will bring a fuel tank from my fishing boat that has the same connections on it and try that too. If neither of those things help, i will remove the carbs for cleaning.

 

[jimmbo]

If you keep running it, and one or more carbs are Starving for Fuel and/or Gummed Up, you risk Serious Engine Damage. Lack of Fuel, means Lack of Oil.

 

[68glasspar]

If you keep running it, and one or more carbs are Starving for Fuel and/or Gummed Up, you risk Serious Engine Damage. Lack of Fuel, means Lack of Oil.

I removed the carbs and opened them up! They are very clean, high speed orifices are clean, all passages clear!

 

[racerone]

Part number of the NOS distributor cap ??

 

[68glasspar]

I did notice something that i just dismissed as a one time thing, but i find some water under the engine cover. Not much, just enough to notice. Can these engines ever have a problem with excessive exhaust back pressure?

 

[68glasspar]

Part number of the NOS distributor cap ??

382480

 

[racerone]

Excessive exhaust back pressure is a far fetched idea.----Remove cowling.----Start motor.----Look for a leaking gasket / hose.

 

[68glasspar]

All the reed valves are in place and a new fuel pump. compressions still 115 to 120. When the amplifier is defective, is it just no spark?

 

[racerone]

Are you sure that is the correct distributor cap for your motor.-----Perhaps another case of --" they look the same"----But are not the same.----Put the old cap on and test run ?

 

[68glasspar]

Are you sure that is the correct distributor cap for your motor.-----Perhaps another case of --" they look the same"----But are not the same.----Put the old cap on and test run ?

I had the problem with the old cap also

 

[jimmbo]

All the reed valves are in place and a new fuel pump. compressions still 115 to 120. When the amplifier is defective, is it just no spark?

Maybe, however, as Electronic Parts warm up, and under Cowl Temps go up, those Electronics can go Wonky, resulting in Weak and/or No Spark

 

[racerone]

Run with a timing light ( 1 cylinder at a time ) and see how spark behaves when motor falters.

 

[68glasspar]

Something to ponder over! While putting my carbs back on the engine and trying to get everything reset i noticed when i turn the key to the on position the choke partially applies. I have a separate toggle switch for the choke and when i work that switch it applies firmly full on. I did a little web searching on choke problems on these engines and found reference to there being an omc service bulletin about the choke staying applied. I guess the choke coil has 2 inputs, one thru the toggle switch and one thru a temp switch. It was surmised that either a weak water pump or a defective temp switch would keep the choke applied. And it was supposed to be rewired to allow just the toggle switch input to the choke coil. Anybody have experience with this?

 

[racerone]

That is correct.-----The fact is that most folks ( perhaps not you ) do not understand how things work.-----Factory attempted to make choke more " automatic " for novices.----Today cars / outboards have a computer that has taken the human factor out of starting / operating engines.----So if the " thermo-electric " function works on your motor I would leave it alone.----And have you tested the overheat horn ?----Replaced the water pump impeller ?

 

[68glasspar]

That is correct.-----The fact is that most folks ( perhaps not you ) do not understand how things work.-----Factory attempted to make choke more " automatic " for novices.----Today cars / outboards have a computer that has taken the human factor out of starting / operating engines.----So if the " thermo-electric " function works on your motor I would leave it alone.----And have you tested the overheat horn ?----Replaced the water pump impeller ?

I retired 1yr ago after working 35yrs as an auto mechanic and currently still an aircraft mechanic! I can read and understand a manual. What do you mean by overheat horn? No reference to that in the service manual. Have i replaced the water pump? Not yet! But if OMC had a service bulletin to rewire the choke is wasn't because it was working correctly. The must of had numerous accounts of failure of that. Next time i float the boat i will use the manual choke button on the engine that will defeat the auto feature when pushed all the way in.