300xs and the fleetmaster disaster

**GLfountain** · 06-29-2015, 01:44 PM

Hi Guys,
I need some advice on replacing the lower on my counter rotation 300xs. The one that is on there goes into gear but the minute I try to plane off she hammers like crazy. From what I've found the counter rotation lower is the weak side. I see mercury is extremely proud of there Fleetmaster and was wondering about the SEI lowers or if rebuilding is the way to go. The case I have isn't windowed or beat up...yet.

**XstreamVking** · 06-29-2015, 02:28 PM

May just be a cable out of adj. Not going in to gear all the way. If you haven't checked it, you may want to.

**kb5050** · 06-29-2015, 02:52 PM

if the adjustment doesn't fix it, it sounds like the clutch dog and where it engages the gear is worn and rounded letting it disengage under load, rebuild or replace. I don't know if SDI makes a counter 3L gearcase. but I've heard they are OK and if they have a problem they warranty them, I've never had one, just what I've heard

**XstreamVking** · 06-29-2015, 03:42 PM

The rounding may be caused by a shift cable out of adj. and not engaging the gears fully.

**GLfountain** · 06-30-2015, 03:19 AM

Thank you for the replies!
Adjusted the cable until it barely went into reverse and it still did it. I'll have to check that clutch dog out. I drained the oil and there wasn't any metal filings/chunks in it. none more then normal anyway. What I don't get is I ran 10 miles and it worked fine, shut it down and trolled on the other motor, started it back up, eased into the throttle and then it started hammering.

**flabum1017** · 07-01-2015, 07:06 PM

Make sure the shift slide where the cable attaches isn't cracked or broken...... had one that cracked and caused the gearcase to di the same thing................

**Superbender** · 07-01-2015, 08:28 PM

Also check to make sure cable is getting full throw.

**XstreamVking** · 07-02-2015, 06:38 PM

You might try shifting into fwd fully manually with the cable disconnected. Shifter might be screwed up somehow not getting full throw. Had one where I had to do this to find the problem.

**Steve2ManyBoats** · 07-03-2015, 01:50 PM

Same here. Once had a teleflex shift cable where the housing was stretching a bit and wouldn't allow full travel to the shift bellcrank on the motor. Unfortunately, it happened while I was out on the bay and the motor jumped in and out of forward guite a few times heading in. Went slow, but by the time I got back to my dock and figured out what was what, my clutch dog and the shift detents on the forward gear were both rounded over and shot. I'm afraid you're going to find the same thing.

Good news it ain't hard to fix and with a new cable you should be good to go.

The definitive test is what XtreamVking suggests. Take off the shift cable, move the shift linkage on the motor to full forward, but it in gear in the water and see if it holds forward gear or not. If not, you'll have to replace the clutch dog and likely the forward gear. If it does hold in gear, you got lucky and it's probably a shift cable with some stretch in the outer jacket.
Good luck...

Steve2ManyBoats

**CharlieN** · 07-03-2015, 03:49 PM

You can also disconnect the shift cable at the engine. With your hand shift the lower into gear, then at the shifter move the shift into gear. Now go back and look at the cable in relation to where it attaches. It should move a bit further than needed.
Also push in at the back of the cable, is should not spring of feel spongy.

**GLfountain** · 07-08-2015, 12:40 PM

Thanks for all the replies! as it all turned out, the lowers were swapped around on the motors themselves. Long story short I tore the clutch and reversing gear up. lesson learned: Never take anything for granted when you buy used motors! Thanks again guys!

**GLfountain** · 04-22-2017, 10:45 PM

Hey guys, I'm resurrecting this thread because I cant seem to keep a counter rotation lower in this boat! I'm now going on my 3rd lower and I'm getting a bit pissed (and broke) to say the least! Why would mercury put a fleetmaster lower on a 300 horse motor if it can't hold it? Anyone have any ideas on why I keep blowing these things apart? I'm not surfacing it or beating on it other then a few wide open runs here and there.

**powerabout** · 04-22-2017, 11:22 PM

Are they giving you wtee on them?

**Todd D** · 04-23-2017, 12:17 AM

The newer fleetmaster that come on a 300xs or any fleetmaster after 2007 has a fatshaft (19 spline) which means it has the same internals as a torquemaster/sportmaster). Not sure why you're having issues but there's probably something else worn in the boat contributing to the failures.

**GLfountain** · 04-23-2017, 01:54 PM

No warranty on them. All the shift cables are new and adjusted. I'm thinking of dumping the fleetmasters for the 4.8 HD offshores. I wouldn't think the boat would be too heavy for fleetmasters ( 31 fountain cc) but I did have a guy say that's a contributing factor especially the counter.