Counter-rotating engines.

[CaptKennyW]

I have twins on my boat, pretty sure the stbd one is the c/r. I have to go look again. My question is...has anyone ever herd that the c/r engine always gives the most trouble? My dad has been doing lots of long neglicted matainance on them and has noticed that the port engine (which always runs smooth and starts quickly) has never been into by a mechanic whereas the stbd one has had a bit of work done to it. Thanks for the help.


Kenny

 

[BobP]

Capt K, only a few parts of the gearbox are different, power head is exactly the same, including rotation.
The starboard motor is usually the standard r/h unit, turns CW when viewed from the rear.

Like any twins, over time they each develop their own personality!

Be sure to keep rpms close to each other so one engine doesn't lead all the time. Don't go by control unit position only. I have to slightly offset one lever from the other at cruise, I would expect fly by wire to eliminate the need.

 

[gradyfish22]

On older engines, there were some cases where the CR engine did have issues with gear boxes and wear, on newer engines most manufacturers have been able to eliminate most of these issues and often the CR engine is heavier by a few lbs due to design changes to offset/prevent some of those problems. If basic upkeep is performed, you should not notice any major differences. As Bob said, they will develop different personality's. My twins also require a slight offset in throttle position to get them in sync(if that bothers you, you can have your throttle cables adjusted to match, but it takes a lot of fiddling with). If I troll and offset my rpm's, I alter which one is at higher rpm's over a set interval of time to make sure they engines are evenly loaded and used by the end of the day.

 

[CaptKennyW]

i guess they are different personalitys, the stbd gives a little trouble. I think i will have to replace both lower units before to much longer though water keeps leaking in them turning the gear oil milky. thanks

 

[gradyfish22]

Kenny, I would fix them quick if water is getting in and the oil is milky, changing the oil is not a solution, that is a bad sign and you could do a bit of damage to those engines if not fixed soon. I know you do not want to hear that, but it is better then the alternative. Have the lower unit seals been changed recently? When you change your lower unit oil do you replace the small seal on the screw? Those are likely causes for leaks and may fix your problem, if that does not do it it may be worse and you may need a new or rebuilt lower unit. If you run the engines with water in the lower unit, you will likely cause more issues down the road. The seals can be done yourself, if you have not done it before, have someone who has give you a hand, otherwise it needs to go to a mechanic. If the seals haven't been changed recently, try that and some new oil, then after a few trips check it, if it has water again bring it in for service, if it looks better just keep monitoring it, it may take a few lower unit oil changes to clear it all out.

 

[jehines3]

Shhhhhh, not so loud guys, I don't want my CR engine to know it is supposed to have a different personality as she is the good child...jh

 

[CaptKennyW]

were keeping an eye on the lower units they have been changed once before my dad is going to tear into them in a few days he retired and needs something to do!

 

[gradyfish22]

Kenny not sure how often the lower unit oil and gaskets are changed, but oil should be around 100hours of use or every season if you put less hours on, and gaskets I do either every 2 seasons or after 200 hours. Every time I change my lower unit oil I change the small gasket on the screw, many guys neglect that and that is a spot where a lot of water can get in and oil can leak out, neither are good. I believe that is what Yamaha recommends as well. Sometimes I feel it is tedious to do this so often, but for what a lower unit costs to have replaced, it is well worth the preventive maintenance, hopefully your day has luck with one of the things I mentioned above and can fix it. If it is only water inside that should do it, if he sees small metal filings inside, that is worse usually and may need more work.

 

[CJBROWN]

Maybe everyone knows already, but a bit of mono fishing line in the prop can work its way into the output-shaft seal and tear it up pretty good.

If you wind one on there, you need to pull the prop and make sure there's no line on the shaft, even if you pull it out and think you got it all. Don't ask me how I know this...

 

[Gman25]

if he sees small metal filings inside, that is worse usually and may need more work.

Dont panic if you see some small metal filings, the lower screw is a magnet and will attract the filings which I always have after changing the lower unit oil.

 

[Grog]

It's good practice to pull the prop every season to inspect the shaft and lube it. As long as the lower unit isn't giving you any problems or there are filings in the oil, just change the seals and go fish'n.

 

[jimmy's marine service]

never heard this "there's more problems with a counter rotating engine"???
engine's are the same,the gear case is different...
as far as gear cases go...braid fishing line is the worst...really tears up the shaft seals...if you're getting water in the gear case,you're gonna need to pressure test and vacum test the lower unit-this is how to locate the leak...vacum test is really important,sometimes the seal will work with pressure,but it will leak on a vacum,hard to believe huh ??? be sure to pay attention to the shafts,if the shaft is burred,it won't seal correctly...
a few metal shavings is normal,this is usallly caused by someone not shifting quickly,if you take it real slow to shift,then there's more grinding,hence,the metal shavings...shift hard and fast,like you mean it...
you really need to service a gear case at least once a season,i like the synthetic high performance gear oil,and allways replace the sealing washers on the vent and drain plug...

 

[BobP]

Was it streaks of milk toward the last of the drain out, no big deal, or does it all look like milk? And did you get out the same amount that went in? Does the lower unit shift properly an dstay in gear?

The dealers don't normally change the seals, they always leak test the unit, if it passes - they do no seals. I had to force my OMC dealer to change all the seals on my 92 Johnnies as a preventive measure, he didn't want to - said he only replaces any one seal when found leaking.
I didn't like that policy.

You may want to take the lower units in and have all the seals replaced, good or bad, even if the dealer balks. Cheaper than $1500 rebuild.
And you may want to get a "parts engine" by buying a working used engine, then you will have a spare lower unit. Even if it's a RH lower unit you can still use it on the port side, just can't use the old LH prop.

 

[gradyfish22]

I agree Bob, I've been using my dealer for years, at first he did not want to change them as often as I liked, but he got used to it and he knows my routine, he now knows to change them every other year for me. I'd rather spend a few bucks extra then have a few days or weeks of my season ruined. My deal is usually packed during the year, so for me it would be weeks more then likely.

 

[CaptKennyW]

bob it looked like milk, and it wont shift very easily into reverse. my dad has been reading up and it and is planning on taking the l/u off and checking the gears in there as well as pressure/vacuum testing them.

 

[BobP]

Capt K - not good.

The major parts in there cost an arm and a leg, hope it's a minor one.

May be difficult getting it apart after all those years.

 

[CaptKennyW]

i already know its going to be expencive, its already been more trouble than its worth and with gas prices going through the roof its just not worth it.

 

[Grog]

Check your messages.

 

[gw204]

You're trouble shifting is most likely due to a toasted shift shaft. Yamaha was using standard steel on those shafts up until the early 90s when they switched to stainless. It's a known issue for them to rust up and snap.

Repairs are expensive and labor intensive (gotta pull the powerhead) and usually end up in a repower.

Hopefully, your shafts were already changed to the SS ones and your problem is restricted to the lower unit. If you still have the original shift shafts and the problem is determined to be in the lower unit, carefully consider whether the motors are worth repairing because their days could be numbered.