| Author |
Message |
    
Ken Foot
Member
Username: kenfoot
Post Number: 4
Registered: 07-2007
| | Posted on Sunday, September 06, 2009 - 11:14 pm: | 
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What started as light knocking turned loud and motor stopped. Flywheel wouldn't budge once home. Dropped the leg off, pulled the plugs and got the flywheel to move a half turn then it binds hard. Feels like the bottom cylinder doesn't have compression. Next moves? I'm happy to rebuild if it can be done without too, too much expense. |
Martin Johnson
Member
Username: martino1
Post Number: 12
Registered: 05-2009
| | Posted on Tuesday, September 08, 2009 - 12:03 am: |
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I would pull the head. You can slowly turn the flywheel & monitor piston movement to figure if it is a bad rod, rod bearing, etc. Unfortunately, it doesn't sound good. I did have one do this to me shortly after a rebuild. Turned out a broken rod bolt. Did minimal damage. Back in operation quickly, after changing all of the rod bolts. |
jamie campbell
Advanced Member
Username: outboard_doctor
Post Number: 578
Registered: 02-2009
| | Posted on Tuesday, September 08, 2009 - 02:14 am: |
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The engine will need a complete rebuild so remove the lower unit and then the head, have a look and strip the rest of the engine down |
Joe Reeves
Senior Member
Username: joereeves
Post Number: 8014
Registered: 02-2001
| | Posted on Tuesday, September 08, 2009 - 11:22 am: |
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Remove powwerhead, tear it down for inspection. You have nothing to lose at this point. |
Ken Foot
Member
Username: kenfoot
Post Number: 5
Registered: 07-2007
| | Posted on Wednesday, September 09, 2009 - 01:59 am: |
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Thanks all for the advice. Pulled the head, slowly rotated flywheel (only rotates 180 anyway till it stops) and could see the top and bottom pistons moving regularely but the middle is loose in behind. On the downstroke I can push it 1/4" in with my finger. Cyinder walls look fine, pistons a bit loose but seem o.k. Next move? |
Martin Johnson
Member
Username: martino1
Post Number: 13
Registered: 05-2009
| | Posted on Wednesday, September 09, 2009 - 11:35 pm: |
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You will need basic tools, a good propane torch to loosen frozen bolts to avoid breaking them, and a factory manual. It will tell you how to remove the powerhead & dissassemble it. You will want to examine the crank and block for damage to evaluate for rebuild. |
Joe Reeves
Senior Member
Username: joereeves
Post Number: 8031
Registered: 02-2001
| | Posted on Thursday, September 10, 2009 - 12:07 pm: |
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Take pictures before dismantling, and make notes as you will not remember certain important things. Tear the powerhead completely down, then separate the good parts from the damaged parts, and go from there...... part numbers, prices, etc. |
Ken Foot
Member
Username: kenfoot
Post Number: 6
Registered: 07-2007
| | Posted on Saturday, October 31, 2009 - 01:10 am: |
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Powerhead is completely torn down. Looks like a connecting rod bolt came loose on middle cylinder. Connecting rod and bearings are shot and I'm told the crank is worn and done. Cylinders and pistons are o.k. The connecting rod bolt broke the top of the leaf plate as it rattled about so I'll need one of those. I've been offered a used crank and connecting rod for $515. New bearings, gaskets, rings etc. bring the price ~$1000. Worth it? I'm leaning toward yes. |
jamie campbell
Advanced Member
Username: outboard_doctor
Post Number: 709
Registered: 02-2009
| | Posted on Saturday, October 31, 2009 - 03:54 am: |
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The 70hp is a good reliable engine it is worth rebuilding in my opinion |
Martin Johnson
Member
Username: martino1
Post Number: 35
Registered: 05-2009
| | Posted on Saturday, October 31, 2009 - 09:38 am: |
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Don't know the year of your motor, but that seems pretty high for a used crank. I would try some other sources. I have purchased used cranks for V6 engines for $100, can't imagine a 70 being that high. I would look for a complete used powerhead, to either use as-is, or for parts. Try picking up a "Boat Trader" type magazine, and look for marine salvage yards in the back. I'm in SW Florida, and we have several excellent ones here. Cylinders and block being OK is great news. I would strongly suggest all new rod bolts. I will never do another rebuild without doing that. |
Chuck Tenge
New member
Username: chucko
Post Number: 3
Registered: 10-2009
| | Posted on Monday, November 02, 2009 - 09:13 am: |
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Theres a 70 johnson on ebay today. Only bid up to 125.00 Its complete. Check it out. A complete used engine, or a powerhead are your best soloution. |
Ken Foot
Member
Username: kenfoot
Post Number: 7
Registered: 07-2007
| | Posted on Sunday, November 08, 2009 - 11:49 am: |
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Are the Johnson and Evinrude 70 hp of the same year the same engines? Are there groups of years that are the same type? I saw a 1978 75hp that looks just like mine. Will the crank be interchangeable? |
