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2002 70HP 2 Stroke Smokey idle, fuel consumption

O

OLM4TE

New member
G,day fellas, hoping someone might have a few insights on a few dramas im having with a new me 70BETO.

Picked up a second hand 70 for my 4.5m tinny and i don't think it's running right. It would over heat near WOT, smokey at idle and seems to burn too much fuel (70L/18gal to approx. 40km/24miles). Is does seem to stumble a bit at idle and is a bit hesitant when accelerating off the line, but runs perfectly when cruising.

I decided to give it a bit of TLC, i did;
-Removed head and exhaust cover and cleaned a bunch of corrosion out, installed new gaskets and thermostat
-Carby clean and carby kits through all 3 carbs
-new plugs
- New fuel pump
- New diaphragm and gaskets for fuel enrichment pump
- Checked throttle/oil pump linkages to spec

After this the overheating issue is fixed, but it's still smokey at idle. The fuel consumption seems too high considering its a very light boat for the size of the outboard. Here's a video of it at idle -
https://imgur.com/a/IaNx9IL

Anything else i should check? I'm going to throw a timing light on and confirm ignition timing, and might take it out and turn off the enchrichment pump after it's warmed up.

Any ideas would awesome, cheers
 
racerone said:
Motor does not sound right.----Does spark jump a gap of at least 3/8" ( 1 cm ) on a test device?
Click to expand...
I'll have to pick up an ignition tester and check it out. Runs great 1/4 throttle and up, maybe charge Coil not making enough juice at low RPM or failing CDI?
 
I'll grab some testers this week and have a look. Cylinder 2 had some light scoring when i took the head off but it passed the fingernail test...
 
OLM4TE said:
I'll grab some testers this week and have a look. Cylinder 2 had some light scoring when i took the head off but it passed the fingernail test...
Click to expand...
You can make a spark tester from some scraps you probably have lying around. Here’s one I made, scroll to post #26.

1965 9.5 HP Johnson MQ-11C - Rough Idle Help

Hello to All, As the senior member of our boating family, I was recently tasked with bringing back to life an old “Turtle”, MQ-11C. By inspection, this motor has lived a rough life, with about the only good things going for it when it arrived at my workshop being that it was not seized and...
www.marineengine.com
i happened to see that yellow bit in a bin so I used it, but you could just as easy drive in two screws & wind the wire around them, or use two staples.
For what it’s worth I bought a $10 adjustable spark tester, which was very convenient to put the plug wire in one hand screw it out to whatever gap you wanted and put the
alligator clip to ground. It worked great, For about a year and a half. This winter was tearing my hair out because I couldn’t get spark. I finally threw the thing across the shop and pulled my old homemade one out and saw it was sparking across a half inch gap..
 
Edchris177 said:
You can make a spark tester from some scraps you probably have lying around. Here’s one I made, scroll to post #26.

1965 9.5 HP Johnson MQ-11C - Rough Idle Help

Hello to All, As the senior member of our boating family, I was recently tasked with bringing back to life an old “Turtle”, MQ-11C. By inspection, this motor has lived a rough life, with about the only good things going for it when it arrived at my workshop being that it was not seized and...
www.marineengine.com
i happened to see that yellow bit in a bin so I used it, but you could just as easy drive in two screws & wind the wire around them, or use two staples.
For what it’s worth I bought a $10 adjustable spark tester, which was very convenient to put the plug wire in one hand screw it out to whatever gap you wanted and put the
alligator clip to ground. It worked great, For about a year and a half. This winter was tearing my hair out because I couldn’t get spark. I finally threw the thing across the shop and pulled my old homemade one out and saw it was sparking across a half inch gap..
Click to expand...
Cheers mate, i thought about doing a DIY had to grab a comp tester anyway so bought one for $20, seems spark is all good.

When all else fails start throwing stuff and swearing! It's fixed quite a few things for me haha
 
racerone said:
Sounds like the motor needs to come apart.----Scoring is NEVER good.
Click to expand...
Definitely not ideal, its obviously gotten hot before due to the corrosion i cleaned out, but they're not deep and you can't feel them. Here's a few pics, #2 with obvious marks, cross hatching still visible;
https://imgur.com/a/5RzenxX

Just did a comp and spark test. Plenty of spark (>10mm) and a very consistent 6kg/cm2 on all 3 cylinders.

Yamaha specs 8.5kg/cm2, so it's down 30% compression at 500hrs (as per gauge and previous owner..)

Is she toast?
 
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