Still haveing problems 1985 150

[jonharper17]

I still have a knock and i cant figure out where its coming from its only happening when you put it into drive it doesnt do it in reverse. Oh yeah this is a Magnum 150 1985 model.....please help...

 

[86RajunCajun]

Re: Still haveing problems 1985 150

Sorry to be blunt but saying you have a "knock" and only that is way to vague to be of any use in helping you what so ever.

You will have to post more details.

Ill give you a few examples of the stuff you can tell us to help us help you.

How loud is the knock?
Where is the knocking coming from <general area of sound>
Does the knock stay at one speed when you raise the engine RPM or does it knock faster and harder?

Have you changed any parts or done any other work to the outboard recently?

You said that it happens when you put it in forward gear but not in reverse, but does it knock when it is in neutral?

If it only knocks when you put it in gear, then it is something in the drive line or shifting linkage.

The drive line is the drive shaft, lower unit and prop.

Shift linkage is the control handle, all the way to the shift arm on the side of the outboard then to the shift rod which had a clutch and clutch dog to engage the gears.

If your engine is knocking up top, it could be a number of things such as detonation caused by a lean condition, usually a lack of fuel will cause this, or a vacuum leak. Can also possibly be a connecting rod is bent or connecting rod bearing is spun, a galled piston to name a few.

We need lots more info, then and only then MAYBE we can help.

Good luck!

RC

 

[jonharper17]

Re: Still haveing problems 1985 150

when i rev the motor in neutral its fine.
i checked the compression and its fine.
it seems to be coming from below the motor, it does get faster when you put it into drive and give it gas, so as the rpm's rise the noise gets louder and faster.
i havent replaced anything yet. i hope this helps you to help me.

 

[86RajunCajun]

Re: Still haveing problems 1985 150

Ok, so it is an RPM dependant knock coming from under the power head i assume in the lower unit or exhaust housing.

So lets think about what is moving down there.

We have the drive shaft which splines into the crank shaft. This drive shaft also holds the water pump housing and componants which are spun by the shaft. Then into the lower unit gear box. In here we have your pinion gear meshing with your ring gear and all bearings and spacers etc etc that compose the final drive output of the engine. Everything in the gear box is pretty much suspect. The only way to diagnose this problem is to remove the lower unit and take it apart for inspection if the problem isnt obvious when the unit is removed and the drive shaft and water pump componants are inspected.

Sounds to me like you have some chewed up gears missing a few teeth in the lower unit or something of that nature. It may be something small or it can be something large and costly.

Gotta get in there and have a look or have someone who knows what they are doing look at it if you dont feel able.

GL

RC