Now that I have your attention... <BR> <BR>I have an I/O and it goes hard into gear. As I am pushing the throttle forward (or backward) out of neutral I am greeted by a very heavy "thunk" sound as the outdrive goes into gear. It doesn't grind, it just goes into gear very hard. <BR> <BR>This is not a new issue...I bought the boat one year ago and it has always done this. I've tried adjusting the idle speed but no matter how low I go, it doesn't seem to help (I've set my idle as low as 600 rpm and it still goes into gear hard). I changed the outdrive oil last August and saw no signs of metal shavings that would indicate my gears are being ripped up. <BR> <BR>I usually get one of two responses from people riding in my boat...1) "Is it supposed to do that?" 2) "That means you have a good outdrive" <BR> <BR>Does anyone have any ideas on what I can do to smooth the transition into gear? Should I be concerned about it? <BR> <BR>FYI I have a 1998 Mercruiser 5.7L engine and outdrive. <BR> <BR>Thanks

No worries every I/O Merc I've been in did that (Clunk).

I've ridden in I/O's since I was a kid and have come to expect to hear a "clunk"...but with my boat it seems to be excessive and is going into gear way too hard.....makes me think something is out of adjustment.

You better take it in then.

There's a shift interrupt switch that might need to be adjusted. It kills the engine for a fraction of a second to reduce RPM's for the shift.

Walt is right take it in. the shift interupter needs to be set or repaired.

If you have a stainless steel prop it will "clunk" much harder than a aluminum prop because of the swing weight mass. the ss is much much heavier and I have tried both on the same boat and went back to the Al because I thought it would be less wear and tear in the long run. When was the last time you add lower unit oil/lube it could need a top off and you should check and add about twice a season

Lower unit oil was changed last August and was fine. <BR> <BR>I'll look into the possibility of the shift interrupter switch. Thanks for the suggestion!! <BR> <BR>I'm a DIY'er and will do everything I can to keep my boat from seeing the inside of a mechanic's shop.

One other thing I did not see posted is, are you slowly sliding it into gear or putting it into gear at a pretty fast rate? The latter is the proper way. Putting an outboard or I/O into gear slowly will cause them to grind the gears.

Walt/Brad - I believe the shift interrupter switch only operates when the boat goes from forward/reverse into neutral (kills the engine temporarly to take the load of the gears). My issue is when I shift from neutral into gear. <BR> <BR>Peter - fast or slow results in the same dramatic "clunk"

I would recommend buying or getting your hands on the factory ervice manual and there should be a section in it on cause and effects with know cures. A chart of sorts. I believe those are a cone shift mechanism and would also ask how many hours on the outdrive? Unfortunately I have only rebuilt an OMC unit, never a Mercruiser, so I am not going to be much help other than throwing an occasional idea/thought out. <BR> <BR>You would also be wise to find a more dedicated Mercruiser or outdrive type website and post your questions there.

<a href="http://www.mercstuff.com/images/shiftcable.jpg" target="_blank">http://www.mercstuff.com/images/shiftcable.jpg</a> <BR> <BR>As I recall: <BR> <BR>A merc alpha one outdrive doesn't have a cone, it is a "dog clutch". It definately does "clunk", and as Peter suggesting, shifting faster is better. <BR> <BR>The merc bravo drive has a cone, smoother shifting. <BR> <BR>Adjusting the shift cable will help if it is an alpha <BR> <BR><a href="http://www.mercstuff.com/images/shiftcable.jpg" target="_blank">http://www.mercstuff.com/images/shiftcable.jpg</a> <BR> <BR>