Mercruiser 250 engine coupler

[rhoades.doug]

Once a Mercruiser engine coupler fails (slips and smokes), does it really need replaced? Or are they able to "recover" and still work satisfactorily?

I have a Mercruiser 250 (Chevy 350) and had to replace the outdrive (model 1) last season. The boat shop said the engine coupler was fine although when the outdrive failed last year, the motor revved and smoked (and it sure seemed like coupler had done its job and slipped/failed). It was a new coupler (as that was my 2nd outdrive meltdown last season! - the first one required a coupler).

The boat (and coupler) has since performed well (for maybe 15 hrs?) until yesterday when after a long hard run (in heavy seas), the coupler appeared to give way (as the motor revved and smoked a bit). After awhile (to cool), it appeared worked ok and got us back in (but i took it easy and only ran it around 2000 rpm the whole way in).

I'm hoping that i can maybe take it easy on it (and maybe run it thru the season) but I'm really thinking the motor needs to come out and a new coupler installed. I do have a lower pitch prop I could use that should help take some torque out of there. It is a big old boat and it does work very hard.

Any advice would be greatly appreciated!

 

[dubs283]

Re: Mercruiser 250 engine coupler

i'm confused, so you have had two new drives and one new coupler in two seasons?

the coupler/drive shaft set-up, if properly installed and maintained should last for a lifetime of boating

it sounds as though there is an issue with aligning the engine coupler, as this can lead to coupler failure rather quickly

also, not greasing the coupler every time the drive comes off can help it fail too

 

[rhoades.doug]

Re: Mercruiser 250 engine coupler

yes - last year was a total nightmare. first the outdrive went but that wasn't such a huge surprise. that one had over 10 years of service (and tons of hrs - if they all lasted that long, i'd be happy). when it went tho, it took out the coupler. expensive, but i thought it just did its job (and protected the engine).

after that, i do question the workmanship. when that next outdrive went (after less than 20 hrs), the boat place said i hit something. i highly doubt that i did and there was no evidence of the sort. that new coupler smoked when that outdrive went but they said it was ok when they put on the next one. it has been working fine but yesterday (with the smoke and rev) was scary to say the least.

outside of getting the motor out and back in, is installing the coupler difficult? obviously there's some alignment nuances (etc.) that you feel may be wreaking havoc? the last outdrive was used but appeared in great shape before going on. is there some reference somewhere where i can get instructions etc. so that i could better understand all this (and maybe even consider doing it myself)?

thanks in advance!

 

[bigskiohio]

Re: Mercruiser 250 engine coupler

yes do it yourself $100.00 for coupler ,$50.00 alignment bar that you should use every year to check,8 hrs of work some guys do it in alot less. your mech isnt doing you any favors. once you do it you wont pay somebody else. plenty of posts and pics on here to read.

 

[dubs283]

Re: Mercruiser 250 engine coupler

is there some reference somewhere where i can get instructions etc. so that i could better understand all this (and maybe even consider doing it myself)?

yep, in the adults only sticky you will find links to download the proper manuals for your engine and drive unit

 

[TilliamWe]

Re: Mercruiser 250 engine coupler

To answer your fisrt question, no couplers never recover. once they slip, they will always slip and get worse. yours is junk.

You have an alignment issue with your engine. You either have had an incompentent mechanic putting on the drive and couplers, or you have a serious problem with the motor mounts/stringers of your boat. I hope it's the former.

 

[rhoades.doug]

Re: Mercruiser 250 engine coupler

thanks a ton everyone!

 

[rhoades.doug]

Re: Mercruiser 250 engine coupler

yes do it yourself $100.00 for coupler ,$50.00 alignment bar that you should use every year to check,8 hrs of work some guys do it in alot less. your mech isnt doing you any favors. once you do it you wont pay somebody else. plenty of posts and pics on here to read.

when you say 8 hrs to install the coupler, does that include the time to get the motor out of the boat and back in again?

 

[rhoades.doug]

Re: Mercruiser 250 engine coupler

To answer your fisrt question, no couplers never recover. once they slip, they will always slip and get worse. yours is junk.

You have an alignment issue with your engine. You either have had an incompentent mechanic putting on the drive and couplers, or you have a serious problem with the motor mounts/stringers of your boat. I hope it's the former.

can a coupler that wasn't properly installed (and misaligned or whatever) actually destroy an outdrive?

that last outdrive we replaced was toast - especially the bottom - but it all looked great before it went in (one month prior). they did say they had some problems getting the motor back in there but i figured that was inherent to the process. (by the way, this is a 1977 24' sea ray weekender)

 

[TilliamWe]

Re: Mercruiser 250 engine coupler

No a misaligned coupler should only destroy the coupler. Even an improperly installed engine should not destroy a drive. But a misadjusted shift cable sure can! And if you have motor mount/stringer issues, and your motor is moving around, it could be messing up the cables and their operation.

Do me a favor, okay? Really check the stringers, motor mounts, and transom VERY closely for signs of rot or damage. I have a bad feeling here...

 

[cr2k]

Re: Mercruiser 250 engine coupler

Another thought...There is a washer/spring stack on the rear mounts if this is not exactly correct you will have coupler failure. As you mentioned they had problems getting the engine back in I would suspect this to be a problem. Take pictures of these when you take apart, maybe you can stick it to the boat shop that may have boogered up the job.

The couplers have aluminum splines so if they go bad they should not hurt the shaft. But if not properly aligned they will self distruct in short order.

8 hours is a good estimate for a first timer/ do it your selfer.

Although a shop will charge you book rate of about 6 to 8 hours a good shop could do it in 3.

One trick...Don't pull the front/side mounts off the engine, just pull the lag bolts out of the stringer. saves tons of time and you are closer to alignment on re assembly. Use tape hold the nuts under the back mounts on re assy too.

 

[rhoades.doug]

Re: Mercruiser 250 engine coupler

No a misaligned coupler should only destroy the coupler. Even an improperly installed engine should not destroy a drive. But a misadjusted shift cable sure can! And if you have motor mount/stringer issues, and your motor is moving around, it could be messing up the cables and their operation.

Do me a favor, okay? Really check the stringers, motor mounts, and transom VERY closely for signs of rot or damage. I have a bad feeling here...

Here's a question I almost hate to ask - If I do indeed have "motor mount/stringer issues" is there a (reasonable) remedy? Or at that point is the old girl about done?

 

[TilliamWe]

Re: Mercruiser 250 engine coupler

You'll have to go to the boat restoration section, and decide for yourself if the remedy is reasonable or not.
cr2k mentions a very common thing with the goofy spring washers in the rear mounts. My dad has trouble with them every time. So maybe that's all it is?