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  1. #1

    Default Johnson faststrike 150 rebuild

    I have a 97 model fast strike 150 that has been a great motor, but a couple days ago I noticed a knocking sound while running. I did a compression test and the top 4 cylinders are around 110 but the bottom 2 are 85 and 95!! So I guess it is time to do something. How hard is it to rebuild one of these, I would like to do some of it myself to save a little money. Is it possible that it just needs a new ring job? Or is it most likely need to be bored out??just looking for thoughts!

  2. #2
    Join Date
    Sep 2016
    Location
    Smyrna, TN
    Posts
    236

    Default Re: Johnson faststrike 150 rebuild

    Sounds like you definitely have a problem with the 85 lb. cylinder. These motors have staggered combustion chambers & compression is lower on #5 & #6. You might see as much as 10 lbs, but 25 is too much. I would suggest you pull that head & take a look. Not hard to do & the motor has o-rings instead of a head gasket. They are reusable. Just need RTV to seal the water passages in the block from external leaks.
    Rebuilds are not hard if you are mechanical minded? The motor will probably need attention on that questionable cylinder. If the motor has never been over heated then good chance the cylinders are still round.

  3. #3

    Default Re: Johnson faststrike 150 rebuild

    Thanks, I am fairly mechanically inclines, so I will prob attempt it myself, and I don’t think it has ever been over heated, could it just need new rings?

  4. #4

    Default Re: Johnson faststrike 150 rebuild

    If you decide to rebuild the motor have the block pressure tested before anything. You need to rule out the casting flaw that appears in some of those blocks.

  5. #5

    Default Re: Johnson faststrike 150 rebuild

    Should I get it pressure tested before I pull the head to look at pistons? Never had a pressure test on one before!

  6. #6

    Default Re: Johnson faststrike 150 rebuild

    Yes find someone to pressure test the block. The V6 loopers sometimes have a casting flaw from bad mold alignment when they are cast. If you have one of those blocks it will be less expensive to replace it. Early blocks had it the worst but the flaw can show up in later blocks.

  7. #7
    Join Date
    Sep 2016
    Location
    Smyrna, TN
    Posts
    236

    Default Re: Johnson faststrike 150 rebuild

    I would pull the head on the 85 lb side. I think you will see a problem with that piston. I do not think rings will fix this problem on that cylinder. All of the motors we pressure tested were always taken apart. They were being rebuilt anyway. You have to seal the head areas, bottom & top of block (where you add the air pressure). You filled the block with water & the 100 lbs of air cause the water to leak. You can see water so you know where the leak is. It is a straight forward repair at that point.

  8. #8

    Default Re: Johnson faststrike 150 rebuild

    Just out of curiosity, when I pull the head, what are things that I will be looking for on those two pistons?? Burnt tops? Grooves in the cylinder walls? Trying to get prepared before I pull them.

  9. #9
    Join Date
    Sep 2016
    Location
    Smyrna, TN
    Posts
    236

    Default Re: Johnson faststrike 150 rebuild

    I think the 85lb hole should be obvious. You could see any of the things mentioned or a dished top of a piston. I would expect scoring of the cylinder walls which would require boring, but you might get lucky. You still need to measure the cylinder for out of round or wear. This particular model is not bad for that unless it has been over heated.

  10. #10

    Default Re: Johnson faststrike 150 rebuild

    Thanks a bunch, I’m going to pull it when I get back home next week,

  11. #11

    Default Re: Johnson faststrike 150 rebuild

    So I took the head off and I really can’t seem to see the problem, the piston head is black colored, but the cylinder walls appear to be really smooth with no grooves? I took pics but I don’t know how to upload them? Any idea how to upload the pics and I will get them up

  12. #12

    Default Re: Johnson faststrike 150 rebuild

    Can anyone tell me where to find information on how to upload photos from my phone to this site?

  13. #13
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    703

    Default Re: Johnson faststrike 150 rebuild

    Click the icon with the tree on it
    Click image for larger version. 

Name:	2DB220F3-5DCF-4EB5-9E30-5CAC903D06C4.jpeg 
Views:	3 
Size:	17.5 KB 
ID:	18283
    Click the tab that says From Computer then click Choose File.

    Click image for larger version. 

Name:	425F3585-CFD3-4424-B17F-CE3FF6A1D900.jpeg 
Views:	3 
Size:	83.8 KB 
ID:	18284

    You should now see a screen that asks where to get the images.
    Click image for larger version. 

Name:	6DECAFC4-AF3F-4B7E-A6B1-729AAE41916B.jpeg 
Views:	4 
Size:	68.3 KB 
ID:	18285
    Go to your library, take a picture, or browse for wherever you have them, and select the picture you want. Youíll come back to the Insert Image screen and your photo should appear in the line next to the choose file button. Next click the words Upload File(s) and the photo should appear in the reply box. Thatís kind of the odd part because on phones itís not clear that you have to press the words Upload File. I think on the computer version that is a button.
    Last edited by kevinj; 07-18-2018 at 08:09 AM.

  14. #14

    Default Re: Johnson faststrike 150 rebuild

    So I’m doing all of that, the photo does appear next to the choose file button, but when I hit the upload file button, the photo goes away and does not come up in the box?? Any idea??

  15. #15
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    703

    Default Re: Johnson faststrike 150 rebuild

    Hmm, not sure. You might need to contact an admin. That is the exact sequence I used to post those screen shots and it worked fine.

  16. #16

    Default Re: Johnson faststrike 150 rebuild

    i guess im new to this, but i dont know how to contact an admin?

  17. #17
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    703

    Default Re: Johnson faststrike 150 rebuild

    Follow this link the the admin's profile and send a private message.

    http://www.marineengine.com/boat-for...er.php?1-admin

  18. #18

    Default Re: Johnson faststrike 150 rebuild

    Ok, I pulled both heads off, there is no visible signs of any problems! There is carbon build up on the pistons, but it’s equal on all of them. The pistons don’t seem to have any slack in them. But the bottom two cylinders are lower compression! Could this be a reed valve broke on that bottom carburetor?

  19. #19

    Default Re: Johnson faststrike 150 rebuild

    Also I had a machinest buddy of mine miked the cylinder walls and he said they are within a thousandth of the standard bore and said there was no issue with the cylinders!

  20. #20
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    2,943

    Default Re: Johnson faststrike 150 rebuild

    If its knocking and low on compression you have a problem...damage could be in skirt area you cannot see until piston is removed. I have seen several of these motors with cracked piston skirts that caused knocks.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

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