Johnson 200 HP, (1995) Slow to reach high RPM

[knotagain]

I recently had my power head rebuilt (blown cylinder). The engine initially ran fine, but now it takes a long time to reach planing RPM whether under a load or not. It appears like it is fuel starved as it will surge a little before climbing to enough RPM to plane out. I have check all the compressions in the cylinders and they appear fine. I have swapped out the fuel pump to no avail. Any suggestions whether is is a fuel problem or an electrical problem? I would appreciate any other tests I could perform to help determine the cause.

Thanks

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

When you say it ran fine initially do you mean after the rebuild? IE - did it accelerate OK after the rebuild and has become slower with time? Or is it slower since the rebuild compared to before when it was healthy?

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

It ran fine after the rebuild and now is slow to reach high RPM. It kind of surges and it goes up the powerband like it is not getting enough fuel.

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

That's possible. If you're using E-10 it could be cleaning the tank and passing the crud to the carbs. Especially if you have a 27 micron filter rather than a 10 micron. When it starts to lose, tap the primer and see if it helps or hurts. If the surging is a sharp up & down it could be losing a cylinder.

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

OK. Another maybe related issue: This past Sunday very slow getting from the lake into the public ramp. It kept stalling in low RPM. Did not try the primer. Could it be the crud has made it to some of the lower jets. On the filter: I take it you would recommend the 10 micron fuel filter? Do you think it would help to take out the jets - clean them and drain the bowls- of course after replacing the filter?

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Yes, a good rule of thumb is that if you even suspect the carbs are dirty then clean them. Remember they supply oil as well as gas. If the motor is still under warranty from the rebuilder I'd suggets letting him take a look at it, just to preserve the warranty if nothing else.

Question - what spark plugs are you using?

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

The plugs are Champion L77JC4.

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

They should be the QL but otherwise a good choice.

Just for kicks, look up under the flywheel nad see if the outer magnets are still evenly spaced and tight.

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

I will check tomorrow and reply back. Thanks!

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Checks the magnets and all seem to be tight and evenly spaced. However, the voltage meter on the gauge will jump around from 13.8 to 15.0 from time to time. Also, it did have a bad coil at one time. Do you think it could be a faulty coil?

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Sure. Or even a dirty ground. That's not unusual especially in salt.

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

What is the easiest way to check for a faulty coil? Thanks

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Check for spark. At least that will show if it has spark initially. I'd start by removing the coils and cleaning the grounds. Can't hurt.

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

I know you can hold the plug against the block, but I have read where this can damage the control box. Your thoughts?

 

[Dhadley]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Doing that should do no damage to the control box. However, if you hold it with your hand, it can be a shocking experience. But that doesn't really tell you much. It needs to be checked with a spark checker and jump the correct gap.

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

I will try a spark checker and let you know what, if anything, I find out. Thanks!

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

I pulled the plugs to check for spark. All were fine, However, one plug had no spark plug gap. I re-gaped the plugs. Hopefully, that was the problem. May take it out today. I will let you know the outcome. Thanks!

 

[d.boat]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

I pulled the plugs to check for spark. All were fine, However, one plug had no spark plug gap. I re-gaped the plugs. Hopefully, that was the problem. May take it out today. I will let you know the outcome. Thanks!

I'm a very unskilled and inexperienced mechanic. About the only thing I know how to do is check the plugs! Usually all that accomplishes is blank stares and mutterings of "well, they look fine..." I did amaze a friend once though - his WOT rpms had dropped from the high 5,000's to the mid-high 4,000s. I suggested he pull his plugs and sure enough one was totally fouled and carboned up. (he couldn't remember ever changing them). He replaced that plug on the spot and got his full RPMs back. He thought I was a super mechanic! Your case would have been another lucky find for me if we were boating together, because, since it's the only thing I know to check, I would have seen the gap problem and you would have been impressed!

Actually, I've now expanded on my knowledge with checking the water separating filter (drain bowl style) because that burned me once. It can also be a quick fix for these sort of problems.

Good luck, I'll be curious what you find out!

 

[knotagain]

Re: Johnson 200 HP, (1995) Slow to reach high RPM

Seems to have been the problem. Boat ran great. Thanks again. It just proves sometimes the simplest solutions work best.