merc. 165hp I/O new coupler problem..

I have 18' 1973 Galaxy bowrider in EC ( original seats!) w/ 165hp merc inline 6 motor. I replaced failing coupler end of last season. I folowed all procedures , alignment tool pulled in out with ease. Today was first run of season and coupler completely failed. After 2 hours of mostly cruising , with several top speed runs previously, all at once motor free revved. I slowed and throttled slowly, but coupler was smoking and would not plane. In a matter of minutes at idle speed , outdrive shaft does not even move , while coupler rubber is turning. Why would this happen with new coupler? It seems to be massive failure of coupler. Motor and outdrive are sound , but NO connection in a matter of minutes. What went wrong with my new coupler? I will have it pulled as soon as I can get the boat to a ramp , but any ideas on this problem would be appreciated greatly. By the way coupler was bought new from NAPA with part number that matched merc.number. Thanks for all input , dave

Re: merc. 165hp I/O new coupler problem..

Make sure the front motor mount is still attached to the frame, if it is you may have gotten a bad coupling

Re: merc. 165hp I/O new coupler problem..

hello<br /> usually coupler failure is related to impact or drive failure on the water side or front mount failure on the hull side with the inline enginges. usually the stringer will rot and the motor will drop and not long after that the splines fail or the rubber overheats and spins.<br /> also check the rear mounts,felt washers and springs. they go bad occasinally. also try lightly jumping up and down on the drive while an observer watches the transom. any flex is to much.

Re: merc. 165hp I/O new coupler problem..

Was there any viberation while running?

Re: merc. 165hp I/O new coupler problem..

, outdrive shaft does not even move ,

Click to expand...

Are you sure the outdrive is sound?

Re: merc. 165hp I/O new coupler problem..

Dave, I had the same thing happen with my 74 galaxy bowrider! Just before I ripped up the floor and replaced all of the wood, foam and had the fuel tank repaired. I encourage you to do this yourself, if your able. It will be a good learning experience. Search "shanky beast", here on the boards. The author, I beleive is "Jason", did a great job explaining just how to do this. lots of pictures too!...sl<br />PS I hope this happened close to shore, and out in big water...sl

Re: merc. 165hp I/O new coupler problem..

Thanks for the input! 1. I did have some wood rot right at the two large screws holing front motor mount to bilge floor. I fixed this by installing a thick 2by 2 piece of aluminum angle across width of bilge , now there are literally 8 screws holding front motor mount in place in sound wood. It does not move at all. (this boat has always been stored inside and never left in the water, probibly why it is still around. There is not one place in the floor that is soft , only slight rot around those motor mount screws where water from bilge leaked around them for 30 yrs.) All rear mount washers etc seemed fine when I did job last season ,but ill check again. This motor fires on first lick after (de)winterization and does not have any excessive vibration. The whole day was smooth as silk , and within 5 mins coupler completely failed. Rubber didnt even melt into chunks like old coupler did ( but did have burnt rubber smell and smoking). I could be wrong about outdrive, but I have personally had it completely apart and rebuilt the top end.What I meant was coupler was spinning but outrive shaft was not turning at all while in the boat. I will know more as I pull outdrive and check rear motor mounts. Strange thing is this motor is mounted solid and is extremely smooth vibration wise. By the way I used alignment tool when I installed and it could be pulled out with ease with two fingers. I dont see where there could be any alignment issue or movement of motor or outdrive. It really sounds like a catastrophic failure of the coupler , Im just not sure how often that happens, or if im wrong and someting caused it to fail. Anyway I will find out more as I get things apart and thanks to all who take the time to give their advice. thanks again, dave

Re: merc. 165hp I/O new coupler problem..

Even with a smoked coupler you should some motion of the outdrive shaft. At idle theres very little resistance from the drive so even the friction from the burnt coupler should spin the shaft some.<br /><br />Maybe a frozen gimbal bearing. The shaft would spin in the inner race so you could still get it to run at first untill the shaft welded to the bearing...

Re: merc. 165hp I/O new coupler problem..

Jack,olbuddy, you wrote...<br /><br />"Even with a smoked coupler you should some motion of the outdrive shaft. At idle theres very little resistance from the drive so even the friction from the burnt coupler should spin the shaft some."<br /><br />how many of these have you spun?<br /><br />Dave, sounds like you have a handle on this, is this coupler the original? like in 30 years old?

Re: merc. 165hp I/O new coupler problem..

Personally none, but what has that got to do with it? I'm suggesting things to check based on Daves posts. If I'm full of it, so be it, its happened before.<br />If you read daves posts he says he just replaced the coupler(not like 30 years old) and said the alignment is good.<br />He also says the stringers have been repaired, are strong and the rest of the boat is sound.<br />Given that information what would you suggest?<br />I guess dave could be wrong about the condition of the boat but I can't say.

Re: merc. 165hp I/O new coupler problem..

Raise the outdrive, straddle the drive and bounce on it several times. Have someone sight down the transom from the side and watch for flex. Boat that age has to have a soft transom which will allow the drive to move out of alignment when in gear.

Re: merc. 165hp I/O new coupler problem..

Update: I rotated prop in both directions by hand and input shaft rotates ( but does not when motor is running and coupler is visibly spinning). Outdrive operates forward and reverse removed from boat with no shaft damage. Gimbal bearing (new from last season) spins easily with no play - no indication of problem there.I also put the alignment tool in , it fits perfect, I wouldnt adjust anything before reinstalling outdrive. Just seems like there is no connection from motor to input shaft through spinning coupler?? I did virtually jump up and down on outdrive before I pulled it out with my 175lbs. There was a very slight amount of movement of rear transom ( not sure if correct terminology) but the back side of boat where oudrive mounts. I could make it flex a little , but I was jumping on the very end of the outdrive. I dont know how much movement should be expected here (if any). I did inspect inside of rear transom, and the wood looks as new. There is absolutely NO visible moisture damage and much of the wood is visible due to cutouts etc. <br /> 1. Does it sound like I just have a coupler that was defective and failed?<br /> 2. Is the minor amount of play in rear transom a possible cause for coupler failure? Hard to imagine from such limited cruising style time. ( by the way the old coupler , probibly original , lasted two seasons (before I reinforced the poor front motor mount/rebuilt upper outdrive/ replaced input shaft u-joints) not several hours like the new one ( cross referenced by mercruiser to a NAPA part number- which saved 40%). Last season <br /> 3.Any other possibilities??<br />I will post more info when I lift motor and get coupler pulled , but so far I cannot find a reason for the failure. Couplers are kinna pricey, and a pain to change out without knowing how failure occured if you know what I mean. <br /><br /> Sincere thanks for all the input received and any other input. I could not enjoy boating at all if I didnt have an older boat that I have to maintain and repair myself. Input from those that have been there and done that before is priceless. Thanks again, dave

Re: merc. 165hp I/O new coupler problem..

new parts do fail.. u seem to have checked all the other possibilities.. some time the only way to really find out is to fit another "new part" and see what happens..<br /><br />u seem to be in that situation..<br /><br />trog100

Re: merc. 165hp I/O new coupler problem..

I did have some wood rot right at the two large screws holing front motor mount to bilge floor. I fixed this by installing a thick 2by 2 piece of aluminum angle across width of bilge , now there are literally 8 screws holding front motor mount in place in sound wood. It does not move at all. (this boat has always been stored inside and<br /><br /><br />unless i am reading it worng you do in fact have some rot issues which may be worse than they look<br /><br />tommays

Re: merc. 165hp I/O new coupler problem..

while the engine is out take an ice pick and hunt for wood rot at the shield area. if your 175 pounds can flex the transom think what the 165 horse power can do. many boats did not have the cutout seaaled with epoxy in years past and moisture led to transome rot at the cut out. while a bad "new" part is possible its rather remote. but they are a tad pricy on that I will agree.