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Impossible to start K&B 7.5 Outboard Pro

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Impossible to start K&B 7.5 Outboard Pro

Old 06-24-2018, 06:42 PM
  #1  
albs6
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Default Impossible to start K&B 7.5 Outboard Pro

I've been trying everything I can to start my slightly older K&B 7.5 (red) Pro outboard motor on a V-Hull I built nearly 20 years ago. I purchased the motor brand new from my local hobby store and had it running for 2 summers without many problems. I typically ran 30-40% nitro. I packed it away in a basement and am now picking up the sport again over a decade later. Only to find I can't get the motor to start. I've read thru many threads on here and it seems everyone found a solution. I'm still scratching my head and could use some help.

Here's a rundown of what I've tried so far:
  • Used WD40 to loosen and grease the motor parts after a decade. It was needed!
  • Removed Carb and Needle Valve and soaked in rubbing alcohol.
  • Purchased new glow plug and new 20% nitro from local hobby store. All they had was 20%.
  • Checked glow plugs glow orange making sure the plug and starter both work. Check!
  • Checked engine has combustion. Check! Seems to still have a hard turn before making a full rotation of flywheel.
  • Replaced fuel line.
  • I can visibly see nitro fuel flow from tank to carb. When priming with throttle wide open, thumb over carb, fuel is spraying into carb with ease. My thumb is wet with fuel.
  • Fuel will exit the exhaust pipe.
  • Fuel needle set 3-8 turns. No difference in settings.
  • Carb set to 1/16" when trying to start after prime.
  • I put a squirt of fuel in carb and glow plug area.
I use a Sullivan motor starter and with glow starter on glow plug will crank on the motor for 30-60 seconds several times and I can't even get a single pop. The engine head and exhaust begin to get hot to the touch when I finally stop trying for a while. I'm making sure the engine starter is rotating CW as I've read K&B turn this direction which is opposite other motors. I have a new glow plug, not specifically for K&B or an MC-9, but what my local store had on hand. They are more airplanes and cars than boats. I have some of the original glow plugs from when I first ran the boat and they still burn orange. I've switched them in and out trying several. I've also slightly loosened the glow plug, about a half turn, as it was recommended to try. Didn't make a difference.

I have not taken apart the actual motor. I don't have the experience yet to feel comfortable doing this. I also don't want to spend $$ on a new motor if I mess it up.

This motor use to run fine with no issues - Any ideas?
Old 06-25-2018, 06:58 PM
  #2  
Ron Olson
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OK, to start with one that might not be so obvious but I did it when running both inboard and outboard engines. Did you reverse the wires for the starter?
You have to watch 20% nitro as generally it doesn't contain enough oil for boat engines unless you use Heli fuel which does run 20% oil.
Yes, it could be the wrong plug doing it also as I've found out in the past. I used the MC-9's in my nitro days as they seemed to work well in anything from .12 to .45, the largest size I ran.

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