1991 70hp johnson

[hants]

please can someone help i just bought a1991 sunbird 150 corsair seller said nothing wrong with engine i herd running on flusher muffs sounded smooth and quiet no nocks or rumbles in and out of gear lovely any way cut along story short took boat to sea started up water out of spout lovely warm up and pulled away opened up throttle would not rev passed 4000rpm .thought maybee plugs no maybe coil no done a comp test 125 in top 125 in bottom 0 in middle took of head middle piston mashed up bad chunks missing head pepperd barrel skored ive been had???? also noticed 3 screws on carbs middle one turned allway in may bee to make engine run .. any idears

 

[WillyBWright]

Re: 1991 70hp johnson

Welcome to iboats and use punctuation please.<br /><br />Awfully hard to read your post. But you were definately screwed. Sounds like one for the courts. You should've been more careful. For every used boat that is running fine, there are ten that the sellers want to ditch on somebody else. In too many cases, people don't sell their boats because they were running just fine. They sell them to get out from under them either financially, structurally, or mechanically. Better luck next time and definately take it for a ride first. If the seller declines, leave it fot the next sucker.

 

[hants]

Re: 1991 70hp johnson

thank u for your words of wisdom.. But that does nt help me. I need to no why its happend . If i rebuild or buy a powerhead will it happen again woz it age related . ps we dont have courts like u do. I have no comebacks on seller

 

[ob]

Re: 1991 70hp johnson

hants,First thing you will need to do is decide whether you plan to perform the corrective surgery or have it done by a reputable outboard shop.If you plan on doing it you'll need to obtain a good manual.The scored cylinder will have to be inspected to see if it can be rebored to oversize demensions and the others will need to be closely inspected for any minor scoring.Cylinder failure was likely due to a fouled carburetor ,so a thorough overhaul of all three carbs would be part of the corrective procedure.Hopefully the engine doesn't have any crank damage.Good luck.

 

[hants]

Re: 1991 70hp johnson

cheers ob. ive orderd a omc manual and im going to take the powerhead of leg . take of all auxiliary's then wait for manual to see wot to do next. When you say fouled carburetor do u mean a blockage? wot are the screws on carbs for? do u think the middle one woz surposed to be in so far compared to top & bottom or do u think it woz done just so it would run.? I think i need some luck

 

[ob]

Re: 1991 70hp johnson

hants,Yeh,by fouled I meant fuel restricted which also translates to oil restricted in a two stroke which causes friction damage.If the particular carbs on that engine have adjustment screws for mix they are idle mix screws.I have no idea whether yours is so equipped or why the damaged cylinders screw was pinched down.John/Rude 70's had different carbs for different years.Some with fixed idle orifices and some with adjustable ones.Sounds like yours are adjustable.<br /><br />In any case,hopefully you can secure the services of a decent machinist to perform a rebore of the hole in question that has rebored two strokes before.Also,hopefully the scoring is not so severe as to not allow a clean oversize.If not ensure that the cylinder ports are chamfered following the machining.

 

[MMTech1]

Re: 1991 70hp johnson

Make sure you go through sync an link when done. Wrong timing can also take out the middle piston.