Johnson Fast Strike 150 Rattling Issues

[motoman]

I have a 1994 Johnson 150 Fast Strike 150 . At the start of spring I developed a rattling noise .At the end of last year there was no rattling . Being concerned I took to a dealership and they had told me that the prop shaft was bent and was out .015 and that had created the knock in the engine. They said that they could repair for $500 to $600 but I would still have the the knock . They could repair it for about $4000 to $5000 , but without tearing it down they could not diagnose it and should go ahead and rebuild . The compression numbers 1) 125 2)125 3)126 4)125 5)118 6) 116 . . I am not sure what to do .One question I have is could damage to lower unit be what the actual rattling is ? Another mechanic had told me to run it till it blows and would cost the same as now or later . That was not a great deal of help . I would like to know what you guys think . The rattling is more prominent at mid range

 

[Rustywrench]

Get a 2nd opinion. Not much wrong with your compression numbers. These motors have staggered combustion chambers. #5 & #6 will be lower than the other cylinders. Lots of mechanics will point to this as a reason to rebuild. The propshaft will have to be repaired, but you may have no problem in your powerhead. Be sure to look for water intrusion on #1 cylinder on this model engine. (Clean spark plug or top of piston, exhaust ports)! Motor will usually rattle at 3500 RPM. I would not rebuild unless someone can pressure test the block.

 

[racerone]

Stainless prop ?-----Try running it without a prop and see if there is noise.-----Inspect magnet on oil drain screw ?----Bent prop may mean that gear teeth took a hit and that is not good for them.------Listen to the lower unit gears through a wooden broom handle as a " poormans stethoscope " when running on a hose.

 

[motoman]

Yes sir , It has a stainless prop . It also has been hit . Will the pinion gear still turn on the crankshaft if is in neutral ? Running on a hose you have to place your ear on the cover and can hear a tick .

 

[racerone]

When the motor is running the pinion is turning both the forward and reverse gears-------When the motor is running the pinion gear turns ! -----The shifting is done in the lower unit.

 

[motoman]

Thank you guys for all the responses . I do have another question . Is it possible to start the engine on the hose so way with out the lower unit installed? That way I will be able to determine if that is where the rattle is coming from .Sorry forall the silly questions but I stress a lot !!!!!! Sorry

 

[Rustywrench]

Yes you can take the fitting out of the back of the engine (where motor water telltale is). Don't lose the o-ring. Screw the hose in there. That will let you run the motor with or without the gearcase. It is designed to flush your engine.