15hp just goes slow

[paul2841191]

I have a 15hp johnson.I think its a 1985.I <br />was going pretty fast then all of sudden it went to slow speed.I changed the plugs and wires and tighten fuel lines . And still it will just barely move. I give it full throttle and it just barely moves. In my yard I crank it up and it seems fine but when I put it in the water it goes slow. This is my first boat. I bought it from a freind .Took it out a few times with no problems.Now it seems like I got a bad deal.PLease help.I even put new gas in it.I had the tank vented.Maybe water got in it?

 

[Solittle]

Re: 15hp just goes slow

Welcome paul - Going to give you some homework. Check out the info below for rebuilding you carb as it has crud in it. Relatively easy for the driveway wrench to do:<br /><br /> http://www.outboardrepairs.com/carburetors/

 

[Xcusme]

Re: 15hp just goes slow

Paul,<br />Did the RPM's drop when "all of sudden it went to slow speed" ?? If they rpm's were high, do a search on the board for spin prop hub.

 

[knobby]

Re: 15hp just goes slow

Here's you a helpful site for your engine.<br /> http://www.pugetsoundanglers.org/Fishing Info/Johnson 9.9_15.htm

 

[JB]

Re: 15hp just goes slow

Hi, Paul.<br /><br />Find out what is wrong before you start tearing stuff apart or buying parts.<br /><br />You may be running on one cylinder. Crank her up on the muffs and disable each spark plug in turn. If one makes no difference and the other kills the engine the one that makes no difference is dead. Check the plug for a hot, blue spark.<br /><br />If you have a good spark to a dead cylinder, do a compression check. If that is okay, inspect the reeds and the bypass cover gasket for loss of scavenging pressure.<br /><br />If neither cylinder is dead at idle, you will need to check her under load to troubleshoot further. Open the throttle under load. Pump the primer bulb. If she takes off you have a fuel supply problem; could be tank, lines or fuel pump.<br /><br />If pumping the bulb does no good, spray some premix into the carb throat. If she takes off, do as SoLittle suggests and overhaul your carb.<br /><br />If none of the above tell you what is wrong, inspect the linkage to your stator to be sure that the throttle is advancing the ignition timing all of the way.<br /><br />Good luck and let us know what you find.