35hp Chrysler Outboard Tapping noise seems to get louder as engine gets warmer.

[Rjzthompson1]

Hello everyone!! I recently put a 'barn find' 1978 35hp Chrysler outboard on my 15' Mckee Craft here in Tarpon Springs, Fl. The motor came out of Indiana and was used up until the owner died 15 years ago, After replacing the clear oil from the lower unit, putting in a new water pump impeller, a carb and fuel pump rebuild and cleaning the points, it runs like a top. Actually gained 2 mph over a 1977 Johnson 35hp I had on the boat until January. The motor makes a tapping noise that becomes more pronounced as the motor warms up. The speed of the tapping increases with the rpm. It isn't overwhelmingly loud and it sounds similar to other 35hp Chryslers on youtube videos. Just louder. I can't hear it past idle as the motor is too loud. Using a screw driver to my ear, the sound is definitely louder around the block area. Is this something to worry about and does anyone have any experience with this type of outboard to be able to direct me towards a fix if needed?

Thanks,

Ryan

 

[wickware]

Try to take a video with a camera to record the sound and share it. I have a 1970 35HP since 1984 and c/n recall a Tapping Noise. Even with vibrating at low idle. It could be something loose or touching. Have you removed the hood, To try and spot the noise.
If I fell it?s internal, I try to use a stethoscope to find the problem. Could it be carbon built up in the cylinder???

 

[Nordin]

Check the flywheel if it is loose to cranktap.

Pull the plugs out and put a screwdriver into the hole and touch to the piston top.
Rock the flywheel back and forth and check/feel for any play.
There could be play in the connection rod to the crank or piston.

 

[Rjzthompson1]

Here's an update: I checked the flywheel and I put a screwdriver into the sparkplug holes and rocked the flywheel with no play. I then pulled each sparkplug while the other ran to see if the sound stopped, and it did not. Below is a video of the motor running in my driveway. Any thoughts?

Thanks!

 

[wickware]

That sounds like more than just play in my IMO! Back to Norton?s suggestions! How much are you torquing the flywheel?s nut? Have you felt for slack at Top Dead Center (TDC)? I feel I am hearing Slack, wear or maybe ?contact [. Are these the plugs used before the tapping started? Check your plugs for any damage.

Repeat you Timing Thought as when the ?Tapping Started?, that might reveal something to check.

Good Luck and Good Video!

 

[Rjzthompson1]

Thanks for the ideas. The sparkplugs came in the motor. They are not damaged and there is nothing out of the ordinary. The compression was 105psi on both cylinders. It is within spec. according to the manual. I've only put around 3hours on the motor and only around 1/2 hour at WOT. The motor runs strong and shifts flawlessly. I checked for play at TDC as well as on the down stroke. There was no movement. I did not use a torque wrench on the FW nut. I just made sure it's really tight.

Thanks again.

 

[Nordin]

That metal knocking sound can be different issues.
Start with checking the timing so it is okey, because preignition can give a metal knocking sound.

Timing should be set at 30 dgr BTDC at WOT and points set to 020.

It could also be backlasch in a piston pin, in a connecting rod neadle bearing or a piston that is ripple in the cylinder bore because of damage.

I have had this kind of knocking in some OB and actually I did not find anything obvious wrong when disassambling it.

This issue can be hard to solve without pull the hole engineblock apart.

 

[Rjzthompson1]

Last night I checked the points and timing as well as ran it in the dark to see if there is any arcing. Everything checked out. And I understand that it may be sacrelidge, but I ran the motor today to so some fishing. I have around $300. total invested in the motor so I figured I would just run it and see what happens. So far, the tapping sound has not increases in volume or changed. Thanks, for the input and I will keep searching for the source of the noise. But in the meantime, enjoy some WOT running across the flats.

 

[pnwboat]

Might try lifting up or gently prying up on the flywheel to see if there is noticeable crankshaft end play. Other than that, I would suspect that you would have to do like Nordin stated....tear it apart.

Make sure you keep the oil/fuel mixture at 50:1 and run it. I would think that if there was excessive clearance on any of the needle bearings (crankshaft, rods), the knock would get really loud as you increase the speed, but it's hard to diagnose by just listening to it.

 

[Rjzthompson1]

So, I figured I would give an update on the motor after about 20 hours of running. The motor still runs and the noise has not gotten any worse. The only runability problem that I have now is that the engine surges a little at WOT. Based on spark plug condition, I believe it is a rich condition. I also replaced the carburetor bowl gasket because of a fuel leak and I believe the condition has gotten worse. I did check the float height and it is in spec. Can the float be adjusted to lean out the fuel mixture? Anyone ever tried this?

Also, on an another note, does anyone have a trick for getting the propeller shaft bearing out of the propeller shaft bearing cage? The manual shows to "tap" it out. I've tried and it won't budge.

Thank, for the assistance and feedback.

 

[wickware]

Can you show a Picture of where you are? I have replaced the propeller shaft seals on my 1970 35HP Chrysler. Are you using a Clymer Manual? Is so, what is the part # you want to remove??

 

[Rjzthompson1]

I have a pdf of the Chrysler Manual. Once the prop is removed, there are two bolts that hold in the cage. The cage comes out without a problem. The problem is getting the bearing out of the cage. Thank you View attachment ob2803 61.pdf

 

[jerryjerry05]

Some heat then ice might help getting the bearing to loosen.