89 GT200 Power Loss After it Warms Up

[jhow0228]

I recently purchased a Ranger bass boat with an 89 Johnson GT200. Today was the 2nd time I've had it out. Ran like a champ when I first took off. Planed out fast and got up to 5800 RPM. The longer it ran, the less I could get out of it. The carbs were rebuilt already and I changed plugs. Any clues as to what this could be? I eventually set it down off pad and tried to plane out, motor could barely lift it back on pad.

 

[racerone]

Is oil injection in service and working properly if it is in service?---------I would do a compression test first before anything else.

 

[Bosunsmate]

Check your sparks next time this happens, might be failing coils or stator etc, happens with electronics when they heat up and are getting to the unwell stage

 

[jhow0228]

Oil injection is in service and is working. Compression was checked when I purchased the boat, was good on all cylinders. I don't remember the numbers but the mechanic that tested gave me 6 thumbs up. I am thinking about disconnecting oil injection though. Just for personal preference and peace of mind. I am going to have the power pack and coils tested next. I had a friend that was experiencing similar issues and it was his power pack. It was also an older model Johnson motor.

 

[oldboat1]

Think that hull has a built-in tank under the seats -- might siphon out some fuel and check for contamination. If you have a water separating filter, would empty the canister (good to do that into a glass jar and let it settle out -- same with sample from the bottom of the tank). Water shows up on the bottom.

 

[boobie]

Do a cylinder drop test on it and see what you find.

 

[jhow0228]

Just an update guys. Had a mechanic check the motor out, seems pretty sure I have an ignition coil going out. He can't be 100% on that diagnosis until we actually get the boat out and run it until the symptoms show, I won't know 100% until Saturday. Will update once we know for sure.

 

[darrjen]

Had a similar problem with my 89 Johnson, take a look at the stator and the surrounding area. If all the manufacturers goo has oozed out it's a goner. Popped a new one on and runs like a champ.

 

[darrjen]

Btw, you can check it out with an ohm meter before you just throw one at it!

 

[darrjen]

Suppose to have like 950+/- 75 or something.. mine was way off, and NO output

 

[jhow0228]

Checked stator, it's fine. Power pack and coils functioning properly. I noticed something on the last test run I made Saturday. Felt like a slight blowout when I was planing out. Pulled prop on it and there was a little bit of rubber coming off the bushing, but the hub is not in obvious disrepair. I have another prop with a good hub in it, just a different pitch. I swapped the prop and will hopefully get it back out this weekend. Will post a follow up with my findings.

 

[jhow0228]

Also, I have checked the fuel, it's all good. I was noticing some erratic tach readings when I had it out last which could be caused by the hub gripping and slipping or could be the rectifier too. Will definitely keep you all posted. Thanks for all the input thus far.

 

[jhow0228]

Prop slip was not the issue. I have noticed my tach has been giving erratic readings. Could this be a sign of a failing stator or rectifier? I have looked around the block and under the flywheel to see if there are any signs of stator meltdown, have not seen anything. Could a stator stop functioning properly even though the coils aren't melting?

 

[jhow0228]

Checked stator, it's fine.

I know I contradicted myself. When I looked at the stator it is showing no obvious signs of breakdown.

 

[jhow0228]

Ok. Going to give an overview of what all that's been tested and symptoms.

Symptoms: Erratic tach readings, no top end power or speed, motor seems to surge as I attempt to reach WOT. Boat used to run mid-60s mph and I'm only achieving 47mph tops. First hole shot is good, but after motor gets warm, it really struggles to plane out, if it does plane out.

Findings: Compression between 100-125 on all cylinders, stator is in good condition, plugs are firing when cold(did a drop test and all plugs affected motor equally), can be intermittent once motor has been ran a short while, checked to see if prop had a hub slipping, was not the problem. I have changed plugs and checked gap. Carbs are clean and jets are clear. Fuel is good and so is fuel pressure.

With this, I'm thinking voltage regulator or power pack(maybe both)... Any suggestions?

 

[racerone]

Post the actual compression numbers.----Or are you saying that that you have a cylinder at 100 psi and one or more at 125 psi ?

 

[jhow0228]

I have one bank that is all at 110 and the opposite bank is 120 except one is 125.

 

[racerone]

Some will argue.-----Those numbers indicate a problem I think.

 

[jhow0228]

We replaced the power pack yesterday and adjusted timing. When we took the old pack off, you could easily see it had been overheated and the plastic filler on the under side was spongy. Lake test tomorrow, hopefully.

 

[BenP]

I had an issue like this and power packed helped on a j90plstc not coils just the paower pack, I am now replacing the rec/regulator because tach is haywire. Let me know what you find out after your test. that heat sink issue with loss of power sounds like my power pack issue