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Tohatsu no rpms and no power

S

sunwest

New member
I have a M70A 1987 Tohatsu outboard motor, Was running fine then just all the sudden now I have no rpms or no power it may move about 2 to 3 mph. But at wot it got real low rps and and pick up nomore. Runs great in out of grear and seem to have fine rmps in reverse. but not foward under load.. rpms are great on muffs in all gears and in 55gal barrel. But under aload in foward no luck.

Whats been done : I have tooken to a boat shop and he took of carbs and soked them and blew them all out, Replaced the fuel lines, New tank, New gas/oil, New filter, New plugs , new plug pack ,new fuel filter, checked diphram on fuel pump, checked compression on both cyl.was good. checked both for spark was good. by past rev gov to check its fine.And checked prop I am clueless please help. only crazy thing is when i take off the #1 plug wire it will die but If I take off #2 it does nothing also the bottom carb dont have suction like the top in less you raise the rpms then it has sucktion
 
what are reeds, it has sucktion when you just idle it up a hair, so the boat guys adjusted it up just a little higher then the #1 but has great suckion at high rpms or when you just idle it up alittle also have a little back fire sometime when i start it not sure if that has anything to do with it.
 
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Reed valves have to to with allowing air fuel mixture into the crankcase # 2 when piston goes up in cylinder #2 .-----------When piston comes down reeds close to compress the mixture in the crankcase.----------------A broken / open reed would interrupt the process and result in no power.------Could also be the lower crancase seal.
 
racerone said:
Reed valves have to to with allowing air fuel mixture into the crankcase # 2 when piston goes up in cylinder #2 .-----------When piston comes down reeds close to compress the mixture in the crankcase.----------------A broken / open reed would interrupt the process and result in no power.------Could also be the lower crancase seal.
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the lower crankcase seal is going to be the one were the powerhead connect to the mid section right? If so this may make sence cause i see alot of oil around this area, and also wwhen I mess with it cast i notice like droplits of oil on water....
 
Update :checked reeds i guess they look ok there is no space realy top is no diffrent then the bottom. I have 120psi on top cyl and 120psi on botton cyl only time I got suction on bottom carb is if I rev It up a little. top carb has lots of suction. I got great spark on #1 top and very little spark on bottom seem very weak....can that be causing my loss of rpms and power in foward under load. Other then that in reverse it rev up fine under load, foward only low rmps and no power out of water runs great, i put in water go to shift in first or reverse it will die... then avenualy it will go. also i can put the #2 plug wire on #1 and #1 on #2 and it runs but it dont make no better suction on bottom. and top seems to still suck great. so is it a spark problem,carb problem,or both


Thanks
 
Spark should be able to jump a gap of 3/8" or 10 mm--------------If the bottom can not do that and the top can, your ignition system needs work.
 
the bad thing about it i just replace that cdi (plug pack) about 6 months ago, Not to change the subject but I went and looked at a 88spl evinrude thinking about changing motors, so I can get parts easyer and our local mech will work on these they wont my tohatsu. is this 88spl a good motor for about 600.00
 
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It was a good motor when it left the factory !------------Before buying it you must check compression.----All 4 must be even on the gauge.---------Most outboards are ruined by folks who know little about running / maintaining a fine piece of machinery.
 
racerone said:
It was a good motor when it left the factory !------------Before buying it you must check compression.----All 4 must be even on the gauge.---------Most outboards are ruined by folks who know little about running / maintaining a fine piece of machinery.
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still working on getting this motor meant time I been messing with my tohatsu. could my carbs bo flooding there selves out ? if so how do I correct this. also when I run it,It smells like it running real rich and lots of white smoke how do you ajust the mixture to correct this. Please help
 
What do the plugs look like? Use your Factory service manual as a guide, and verify the carb settings, as well as link and sync. If this sounds like martian to you, seek the advice and assistance of a local outboard mechanic.
 
the sparkplug on tope is little is little black and wet the bottom is clean.. I have to get a manual the mech wont working on it around here I have to drive 3 hours to closest mech that will work on a tohatsu
 
I had this same issue on a ns90a .It ended up being the butterfly in the carb was closed when at idle .The carbs were a little out of sync . Re synced and now I have suction on all carbs.
 
You are clearly in over your head at this point. Get out your Factory service manual, and using it as a guide, start diagnosing fuel, mechanical, and electrical systems until you find the issue. If that seems like it is beyond your capabilities, get the assistance of a mechanic who can help you.
 
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