1955 Johnson 5 1/2hp head gasket

[KonaB206]

I am getting close to 50 psi in one cylinder and a little over 60 on the other cylinder. I was wandering if I am doing the compression test correctly by pulling the starter as many times until I reach the max # psi on the gauge where it doesnt go up any farther and then stop and that is my reading? Are you supposed to put a little oil in the cylinders first? I did put a little spray of pb blaster in each one before checking the compression just to make sure there's not too much friction and damage the cylinders any.

Also Is it possible if I change the head gasket out it might help the compression equal out and maybe even get a little higher on both cylinders?

It looks pretty quick and simple to change it out. I did go ahead and order a new one I found it on Ebay for 6$ so I figured even if I dont do it right away that's cheap enough to have one laying around if I ever needed it.

And one last question if I do go ahead and change out the head gasket what would be the torque sequence and specs for the head bolts?

Thanks, Andy

 

[Crosbyman]

kind of low but before swapping the head gasket just run good decarb like Merc power tune follow instructions….run the engine a while see what effect that does on compression numbers


remeasure

openning up the cyl head is not a big issue but it may not be required at this stage ...depending on your goals and usage needs

why not visit the boatinfo.no site click the stack of books at the top go down to johnson manuals and click on the red book

all you need to know is there … most critical is your impeller !!

 

[oldboat1]

If not removing both plugs while testing, should do that and retest the way you describe.

 

[KonaB206]

If not removing both plugs while testing, should do that and retest the way you describe.

Okay, I was leaving one plug in while I had the gauge on the other cylinder. I will take both plugs out and redo compression test and let yall know how it goes

 

[KonaB206]

kind of low but before swapping the head gasket just run good decarb like Merc power tune follow instructions….run the engine a while see what effect that does on compression numbers


remeasure

openning up the cyl head is not a big issue but it may not be required at this stage ...depending on your goals and usage needs

why not visit the boatinfo.no site click the stack of books at the top go down to johnson manuals and click on the red book

all you need to know is there … most critical is your impeller !!

I might definitely try the merc decarb as soon as I get it running. I got this motor off of craigslist not running for 50$
without a tank and pressure fitting connector. So far since I have bought it I have rebuilt the carb, disassembled the lower unit and resealed it, put in new impeller wear plate and impeller, new water pump gasket, new shift rod oring with new brass bushing, new powerhead to lower unit gasket, new points and condensers and readjusted the points using the voltmeter method. I also purchased a pressure connector from a member on here that seen one of my previous posts and offered to sell me a connector. I think I'm pretty close to be able to getting ready to try and start it up for the first time very soon. Pretty sure all I have left to do is get some dual line air fuel hose, new carb and air hoses to the Male connector on the motor, gap and install new plugs, fill lower unit with fresh oil, mix up some oil/ gas and start her up! I just want to make sure compression is where it should be and have everything checked and fixed first before I try to start it for the first time

 

[racerone]

Compression is the first thing to check out on a $50 new purchase.------Good idea to pull the head.----The original gaskets were not the best anyway..

 

[F_R]

50-60 psi is something wrong. It might come up after it is ran a bit. If it will start. Let's hope it is the head gasket.

 

[KonaB206]

Is there a torque sequence when installing the head and is there torque specs for the head bolts or just tighten well?

 

[racerone]

Bolts are 1/4-NC and torque is 60 / 80 INCH LBS-------The head will be warped ( they all are ) and you need to make sure it is flat before installing.-----Sandy paper on glass works well.

 

[KonaB206]

Bolts are 1/4-NC and torque is 60 / 80 INCH LBS-------The head will be warped ( they all are ) and you need to make sure it is flat before installing.-----Sandy paper on glass works well.

Thank you. Would you happen to possibly know where I could find 1/4 nc bolts?

 

[Crosbyman]

hardware stores have them … I wrap them in teflon tape some use anti-seize goo

make the cyl head flat by laying a 120 grit sheet on the dead flat surface and doing circle 8 figures till all the surface is shiny

no glue on the gasket

bolting sequence basically side to side then redo progessivily till you meet the torque spec

 

[oldboat1]

Got spark? Should check before trying to fire up:

You should see about 3/8" strong spark when measured (testing ignition strength to see if work needed). Remove both plugs and test top and bottom leads, making sure to find a solid ground for the tool -- cheap, btw, and available at most auto parts stores.) Always do easiest testing first.

 

[KonaB206]

I removed the head cleaned head surface with the sandpaper and Installed the new head gasket and now I am getting 90 psi on the lower cylinder and 60 psi on the upper cylinder I took several pictures of the inside of the cylinders which I can post too, but I didn't see any scoring In there.
I did notice the upper cylinder had allot more carbon build up on top of the piston

 

[KonaB206]

Here are some pictures I took of the cylinders with the head off.

 

[racerone]

Carbon build up on pistons is normal.-----Not something I worry about..-----Sounds like it might have sticky rings.-----Start it up and see what happens.

 

[Crosbyman]

I know compression is important but for 50-60 $ most of my oldies were not steamrollers

all had what would be considered d low pressure levels but you know what … they all run great considering they are 6 0 year old engines.

they may not be screamers but for general fishing needs (trolling mostly and more importantly " not rowing" ) they are fine and folks I sold then some for $150 to recoup my parts and motor costs, are happy campers.

as racerone indicated … just run a good dose of decarb sprayed in the carb … let it sit 20 min and fire away

do it twice if you have to

let us know how things work out

 

[KonaB206]

I know compression is important but for 50-60 $ most of my oldies were not steamrollers

all had what would be considered d low pressure levels but you know what … they all run great considering they are 6 0 year old engines.

they may not be screamers but for general fishing needs (trolling mostly and more importantly " not rowing" ) they are fine and folks I sold then some for $150 to recoup my parts and motor costs, are happy campers.

as racerone indicated … just run a good dose of decarb sprayed in the carb … let it sit 20 min and fire away

do it twice if you have to

let us know how things work out

Awesome I'm hoping for the best, im getting very close to starting it up for the first time. I will definitely do a decarb.
would you happen to have the link for the process of that.
I searched on the forum but can't seem to find it.

I will keep yall updated on how things turn out will might try to take a video and somehow post it as well.

 

[Crosbyman]

Mercury has a decarb spray in the carb & wait 15-20 min. product called POWER TUNE which apparently is effective

visit utube or google it lots of info

BRP also sell a decarb "mix in the gas" product

and you can always try a can of SEAFOAM which did fix up my snowblower carb wise nicely this winter . Some folks like it some don't
https://www.youtube.com/watch?v=BXcfsmuruc0

just follow instructions on the product container