Johnson 150 no revs, and blow by.

[gspointer]

Hi, I have a 1983 johnson 150. Due to work etc. I have been unable to use my boat for 5 years. (it ran great 5 years ago) This year I was determined to use it. I rebuilt the carbs, and put in clean pre-mix. I fired it up, and it ran rough and coughed on the muffs. I shut the water off for about 30 seconds and the idle smoothed right up. I replaced the water pump (I was going to do this anyway, partly why I wasn't too concerned running for a few seconds without water), put it on the muffs, and of course it still runs bad. I hoped, silly I know, that I had too much pressure on the hose, and took it to the lake. I am sure that few here are suprised to hear it runs like crap. No hole shot, 2200 rpm tops, (picks up a few with the key pressed in) and lousy idle.

So, I pulled the exhaust plate and found the port side to have a moist oily film on the exhaust plate, (exhaust side), while the starboard side is very dry. Also the starboard side has about 1" of blow by visible on each piston. The port side looks great.
side note, I tested one recirculation valve, it passes air/fluid in both directions. (I will test the rest, but my syringe didn't fit, so I used my mouth, I do not like the taste of gas)

My questions are.

1. Any chance a de-carb will fix the blow by?
2. If not, can I split the case with the powerhead on the boat, remove the con rod caps, and replace those three pistons and rings, or will it require complete tear down and rebuild. (the walls looked good, but I will pull the heads to make sure.)
3. Any Idea why this is on 1 side only?
4. rebuilt powerhead is about 3k, rebuild kit about 1200. How tough is a rebuild?

If needed I can provide pics. Thanks in advance.

 

[jonesg]

Re: Johnson 150 no revs, and blow by.

Get a compression guage and see whatchagot.
Give it a good soak with seafoam directly on the pistons, then a decarb treatment. Then do anuva compression check. See if it helped.

Clean those recirculation valves or replace them.

 

[gspointer]

Re: Johnson 150 no revs, and blow by.

The rings on 1, 3 and 5 are stuck. I have the head off, and am soaking in seafoam deep creep. I will do this for a few days till I get my gaskets. Crosshatch is still in good shape, but there are 3 lines that are shiny, without crosshatch in the #1 hole. I should probably rebuild, but just don't know about putting 1800 or so into this motor. I have yet to find any evidence of any blown gaskets. Is it possible the T-stat was stuck open, and the motor really never gets to operating temp? (The lakes I fish are small and the motor probably runs for less than 15 minutes at a pop.)

I still don't understand why the idle cleaned up so well when I shut the water off. I guess there may have been a leak in a gasket, I just can't find it. I think I will soak for a few days, re-assemble, de-carb with a small gas can and sea-foam, do a comp test, take it to the lake and de-carb with a can of the old merc power tune, and comp test again. if I cant get it running decent without a rebuild, I am leaning to parting it out and getting a new or newer motor.

 

[emdsapmgr]

Re: Johnson 150 no revs, and blow by.

Possible internal water leak. Did you see any milky liquid appearance in any cylinder? When the engine is idling, pull a spark plug wire off the plug and see if it makes any difference to the rpm's. Repeat for the other 5 wires. That should tell you which cyls are not firing correctly. Have a look inside those cyls. Possible to get water leaks from the exhaust covers. An inductive timing light will show you the spark condition on each plug wire. That engine has twin identical power packs which can be switched for testing purposes.

 

[gspointer]

Re: Johnson 150 no revs, and blow by.

I have already pulled the exhaust covers and starboard head. With the exhaust covers removed, I was able to see the blow by on the 3 starboard pistons, as well as the stuck rings. The rings are stuck pretty tight. There is no visible gap between the rings and the ring groove in the pistons. The port side looks great. I am currently spraying seafoam creep into those jugs hoping to free up the rings.

 

[gspointer]

Re: Johnson 150 no revs, and blow by.

I have been spraying seafoam onto the top of the piston, and into the exhaust ports for a couple of days now. The top rings will move, but not nearly as much as the other side. The bottom rings are still stuck tight.

If I am able to free up the top rings pretty well, but not the bottoms, does anyone think I will have any luck putting it back together and doing a de-carb? I am considering buying a different boat tomorrow and putting this motor on the back burner till winter, then pulling it and doing a complete rebuild/bore on all 6 holes.

 

[gspointer]

Re: Johnson 150 no revs, and blow by.

Here is a pic a starboard piston/rings. 1, 3 and 5 are all the same.

This is the port side. (once again, all port side pistons are the same)

This is the most severe scoring out of all 6 holes.

 

[emdsapmgr]

Re: Johnson 150 no revs, and blow by.

The carbon around those starboard rings can cause problems if not tended to. The carbon buildup will prevent the incoming fuel/oil mixture from getting to the top rings on that side. It can cause the piston to overheat and the top ring to snap and break into pieces. Continuing to try to dissolve the carbon is a good idea. You can remove the intake side covers in order to access the pistons for cleaning on the side opposite the exhaust. The Bombardier aerosol product called Engine Tuner is another good product for attacking carbon.

 

[gspointer]

Re: Johnson 150 no revs, and blow by.

That pic is after a week of spraying it down with deep creep at least 2x a day, and about 10x a day over the weekend. I got a different powerhead, and as soon as the flywheel pops, I am going to swap them I will rebuild this one over the winter.