How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Charles Your Own Question
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3929
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
Type Your Boat Question Here...
Charles is online now
A new question is answered every 9 seconds

I have 1990 larson with a gt 175 johnson 1989 it has a miss

Customer Question

I have 1990 larson with a gt 175 johnson 1989 it has a miss fire at low rpms ( water hooked up ) when it missfires ,standing behind it running ,the left bank , a puff of exhaust comes out someware at the base of cylinders , can't really tell due to all the electrical in the way any ideas
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.
Hello, my name is***** will assist you.Do you have the full model number off the engine?
Customer: replied 1 year ago.
Expert:  Charles replied 1 year ago.
Thanks, ***** ***** could be coming from gaskets 21, or 37, or 39. The best way to locate it is to move the electrical wiring and look for some water as well as exhaust. Let me know what you see, and we can go from there.
Customer: replied 1 year ago.
I've replaced gasket 37 and 39. I didn't go farther into the motor. I've been a diesel mechanic for 31 years, but this is the first time I've worked on an outboard.
Expert:  Charles replied 1 year ago.
Still getting the puff of smoke, if so, do you have the equipment to do a leakdown test on the port side. Take out all 6 plugs, install the gauge, then use a 1 7/16" socket to roll the engine over to bring the pistons to TDC. Lister around that cylinder head to see if you can hear the leak.
Customer: replied 1 year ago.
I did a compression check on each cylinder and they were at 100 to 103 wide open throttle.
Expert:  Charles replied 1 year ago.
but a leaking exhaust gasket will not show under compression.