MossBack Posted April 2, 2014 Posted April 2, 2014 I have a 1999 merc 9.9 2 stroke that was running fine last year, a while back when we ran it for the first time since winter we noticed that when running mid-full throttle the water stream goes at full pressure like normal then suddenly acts like it loses pressure and stops spraying for several seconds and then starts back up for a few seconds as the process repeats. Also at idle the water just dribbles out. We put a new impeller and water pump kit in it and the problem is still there. Any ideas what could be causing it? Quote
Super User rippin-lips Posted April 2, 2014 Super User Posted April 2, 2014 Maybe the line has some crap in it. I had to run a coat hanger down through mine last season when it lost pressure. Quote
Super User Way2slow Posted April 2, 2014 Super User Posted April 2, 2014 Again, not a merc guy, but it should have a thermostat. If it does, might want to replace it. Quote
Super User WIGuide Posted April 3, 2014 Super User Posted April 3, 2014 Check the thermostat. It should be held in by two screws so it's not a big undertaking to get it out. Make sure there's no gunk in it or anything that would obstruct the water from flowing through. I don't have experience with that particular motor, but most have a cap that comes off and the thermostat is separate from the cap. You can replace the cap itself without the thermostat and run it to see if it does the same thing. The other thing you'll want to take into consideration as well is the water temp. If it's super cold it could possibly be cycling just fine, but that's usually in almost frozen or salt water if at all. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.