1988 225 johnson v6 throttles down after running full speed for long periods

[fire tech]

fished today, trolled around for 3 hours decided<br />to go to 45 min rock which is about a 10 min ride in calm seas. so i started off and about 8 min.s in my motor shook and throttled down by itself to about 2500 rpm.s no over heat alarms though.before this trip i installed new thermostats and a new water pump.<br />need some help on this one.<br /> thanks: GARY H.

 

[Joe Reeves]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

Fire Tech.... If the alarm doesn't beep momentarily when you turn the key on, double check your alarm system by having the key in the ON position, then ground out one of the heat sensors at the cylinder heads. The horn should sound off constant and steady.<br /><br />(Compression & Spark Test)<br /> <br />1st - Regardless of what problem one might encounter, always start with the basic troubleshooting procedure. Check the compression which should be in the range of 100+ psi (somewhat less on the smaller hp engines) and even on all cylinders.<br /> <br />2nd - With the spark plugs removed, rig up some type of spark tester whereas you can set a gap to be jumped. On magneto ignition systems.... and also the Battery Capacitance Ignition system OMC engines from 1968 to 1972, set the gap to 1/4". On the solid state OMC ignition systems from 1973 to the present, set the gap to 7/16". The spark should jump the gap with a strong blue lightning like flame.<br /><br />Check to see that the timer base linkage did not pop out of the related bracket. That would result in having the spark returned to a full retarded spark position.<br /><br />Let us know what you find.

 

[fire tech]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

DR. REEVES CHECKED COMPRESSION OK<br />CHECKED SPARK PLUG WIRES OK, CK SPARK PLUGS OK<br />CHECKED SPARK PLUGS FOR FIRING ALL FIRED EXCEPT <br />STARBOARD BOTTUM CYLINDER, CHECKED COIL BY USING<br />MIDDLE CYL. POWER PACK WIRING THAT COIL THEN FIRED OK SO THAT BOTTUM COIL IS GOOD THIS LEAVES I THINK THE POWER PACK CRAPPING OUT GOOD OLE ELCTRONICS I JUST REPLACED THE POWER PACK 3 MONTHS AGO! WHAT DO YOU THINK?

 

[93bronco]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

that sounds similar to what i experenced with my 120/140 last year.<br />i had replaced the tstats with the new black ones and before the end of the trip it did the samething - shook & then dropped rpm while running rough.<br />but i had a list of things that it could have been.<br />-<br />i went back and looked at the old white tstats i took out - found them empty.<br />that led me to pull heads to check gaskets.<br />motor was supposed to have been rebuilt when i bought it. <br />i believe now that tstats were removed to hid a bigger problem.<br />head gasket failure was just one of 1st things i noted on the list.

 

[Joe Reeves]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

Fire Tech.... You say that you have no spark from # 5 coil (bottom starboard) but that the coil is okay (your test proves that).<br /><br />It's possible that the pack has failed, but before replacing the pack, check all of the pin and socket connectors etc. You could be lucky and simply have a loose, broken, or dirty connection somewhere.<br /><br />Also, keep in mind that the timer base assy consists of six (6) sensors, one for each cyl, coil, SCR, however you want to look at it. Make a note of which color sensor wire goes where, then switch them around so that a different sensor will be firing that #5 coil. Crank the engine with the s/plugs out and check the spark.<br /><br />If that # 5 coil is now firing, there is a faulty sensor within the timer base. If #5 still does not fire, the pack is at fault.<br /><br />Double check the spark after returning the sensor wires to their proper position as that action may have just cleaned a dirty connection.

 

[fishcanyons]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

Joe Reeves:<br /><br />That's excellent advice. <br /><br />I'm experiencing similar problems with a '94 Johnson 225. After 5 - 10 minutes wide open it drops to 4700 rpm and erratically sputters back up to full speed. When this is occuring the motor runs at either 4700 or 5500, nothing inbetween. Do you think I have a similar problem?

 

[nebraska_woody]

Re: 1988 225 johnson v6 throttles down after running full speed for long periods

without wanting to clog up the system by starting my own thread on the same topic, maybe someone can assist me also on this same issue. 1989 GT200... does the same thing as the previous two also, only mine only takes a few minutes at most (not everytime.. but on a fairly consistant basis)to do that. Mine doesn't pick back up right away though, it will actually fall to "rough idling" and then die completely before I can start it up again and get the motor to run strong again. It's really a pain when pulling a skier..lol.Any ideas folks???