Johnson 90hp flywheel bad?

[wallyuwl]

1985 90hp Johnson v4.

It makes a rattling/ticking noise in the water. It is more noticeable if you are going kind of slow then accelerate a little (louder during the acceleration phase). Increases in frequency with increasing RPM (usually... see below for exception).

Took the cover (cowling) off while in the water and it definitely seems like it is coming from the flywheel or something attached to it. From what I could tell nothing was rubbing against it.

Ran it WOT for 7 or 8 miles. Stopped and did WOT again a few times. Each time once RPM hit about 4400 (maxes out 5000) the noise stopped and it ran like a top! Still seems to run good at lower RPM except the rattle, though maybe slightly rough (hard to tell being an old 2 stroke).

Got home, put it on the hose with and without the cover and no noise. Put my torque wrench at 100 ft lbs and the flywheel nut was/is tight. I have put on the hose previously recently (no rattle) and recently took off and put back on flywheel to make sure was tight.

The weird part is it only makes the noise in the water where there is back pressure.

Maybe flywheel magnet going bad? How do I tell if magnet is becoming delaminated (what to look for)? Maybe drive shaft problem?

 

[racerone]

I doubt flywheel is the issue.----Post actual values of a compression test.----Check gear oil.

 

[wallyuwl]

I doubt flywheel is the issue.----Post actual values of a compression test.----Check gear oil.

All compression 115 to 119 (got a new gauge). Gear oil isn't leaking and has about 2 to 3 hours on it since changed.

Next step take off flywheel and look for problems? Are there bearings between flywheel and lower unit? Wonder if bearing (3 or 11 in diagram below) maybe are bad? What type of noise would a bad bearing make?

https://www.marineengine.com/parts/...turer=Johnson&section=CRANKSHAFT+&+PISTON

 

[jimmbo]

You forgot about the Center Crankshaft Bearing #s 15,18, and 23

 

[racerone]

#23 is the connecting rod.

 

[jimmbo]

#23 is the connecting rod.

Yeah, Damn it. Put the GD # next to the center Bearing...

 

[wallyuwl]

Would there be a knocking if camshaft itself was bad? Everything I have seen is flywheel play with rattle is probably the upper bearing, and if no knocking crankshaft is probably fine. But nothing has been definitive. Rattle/tapping just started within last 2 hours of use.

Does it take special tools, or have to open up the whole engine, to replace crankshaft? I have the factory repair manual.

 

[jimmbo]

It is a 2 Stroke, of a Design that does not have a Camshaft(2 Stroke Diesels do)
No Special Tools are needed. And the Crankcase has to be split to get at the Crankshaft. However, unless it is the Center Bearing, the Upper and Lower Bearing are serviceable, with out splitting the Case
It a 1985, is the VRO working?

 

[Faztbullet]

Could be a broken tooth on pinion in gearcase. The noise traveling up driveshaft to crank. Seen a couple of V6 do this.

 

[wallyuwl]

It is a 2 Stroke, of a Design that does not have a Camshaft(2 Stroke Diesels do)
No Special Tools are needed. And the Crankcase has to be split to get at the Crankshaft. However, unless it is the Center Bearing, the Upper and Lower Bearing are serviceable, with out splitting the Case
It a 1985, is the VRO working?

Thx. Will look in the factory repair manual a bit to see more. Maybe will replace upper and lower out of caution. VRO was taken out 20 years ago, I mix 50:1 oil in gas.

 

[jimmbo]

That Upper is priced at about $400(us)

 

[wallyuwl]

That Upper is priced at about $400(us)

I can get it $150 to $200 new on ebay. Or like $50 used but would get new.