Restoration of 1964 3hp Johnson JH 19A

[Monte NZ]

Hi All

Regarding the above, which has compression of 65psi on both cylinders, what increase could you reasonably expect by honing and fitting new rings?

Your comments would be most appreciated

Thanks again.

Monte NZ

 

[fleetwin]

Well, I wouldn’t mess with it.  These are low compression engines, so your 65PSI reading is not surprising.  Keep in mind that compression readings are oftentimes a little low due to limitations of the compression gage to compensate for such small combustion chambers.

I would remove the head and exhaust cover, and inspect pistons and cylinders as best you can.  If all looks OK, I would clean everything up and “rough up” the cylinder walls with some light emery/crocus cloth, check head/block/exhaust cover for flatness and reassemble with sealer.

[lindy46]

65psi is fine for that motor. Leave it alone.

[Mumbles]

Unless you are removing the pistons and rings, I’d leave the cylinder walls alone as the rings are already seated as good as they will get. That’s just me though.

[fleetwin]

Perhaps it is best not to mess with it at all.  Service the ignition/fuel/water pump and run it, will be fine I’m sure…  Most of these old engines really never get enough time on them to require a “rebuild”.  There is no evidence of overheating (no badly discolored/burnt paint) on the head and block)?  Keep in mind the exhaust cover is not water cooled, so the paint will be burnt off that piece.  There is no real reason to pull the head/exhaust cover unless you see evidence of a major leak or overheat.  The compression is about normal for one of these and even on both cylinders.

[Monte NZ]

Hi Fleetwin and Lindy46.and Mumbles
Sorry for the delay in replying to your posts…….computer keyboard decided to pack up!!!

First of all, thanks for your comments and advice.
In reply,I have done as you all suggested. Also, as several head studs threads were stripped, I fitted helicoils to all 6.
I also lapped both the head and the block .
I have run the motor for about an hour so far. Yesterday I rechecked the compressions and was surprised to see that they had both increased from 65 to 70 psi!
The motor has been completely repainted and after running it I expected the paint on the exhaust manifold to discolour. At this stage that hasn’t happened,
but I’m sure that will happen after some full throttle running.

One thing I have noticed and I would be very interested to hear your thoughts, is I can hear an intermittent rattling sound at idle speed and am wondering if it could be
wrist pin or big end bearing noise.

Thanks again for all your help.
Monte NZ

[crosbyman]

did you retorque the head bolts after the  run ?

Joining AOMCI has priviledges 🙂

[lindy46]

Rattling could be the recoil starter.  I had a 1958 Lightwin that rattled and it was the recoil. Seems I remember adjusting the rope length a little and it solved the problem.

[Tubs]

Another possibility is the magneto advance lever.
Tubs.

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[Monte NZ]

Hi crosbyman, lindy46 and Tubs.
First of all crosbyman I have to make a very embarrassing confession! I did retorque the head bolts, but in doing so, discovered that I had only torqued them to 50 inch!!!! ………must have got sidetracked by a phone call or something and forgot to complete the job……..I have now done them to 80inch!.
In reply to your suggestion lindy 46, I removed the recoil unit and started it with my drill, but the rattle is still there.
Tubs, I checked the magneto lever and that seems fine.

A point I would like to mention with running of the motor is, that I noticed it wasn’t idling as well as it had previously, so I did a compression check and discovered that compression had dropped to 50psi. I then gave it a good dose of Sea Foam and let it soak overnight and after another run compressions were back to 65psi, so it looks like sticky rings were the cause.

Thanks once again for your replies
Monte NZ

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