ZF BW165 Leaking…and slipping?

[Nicholas]

I’ve got ZFBW165 mated to 1200 hp man’s.  The port oil cooler has been leaking. I plan to remove it and hopefully its just a matter of replacing the o-rings where it mounts to the gear box. 

However, I now have a new problem that may or may not be indicative of the cooler failing all together. 

Recently, I had my port trim tab fail while underway (boat is a 58 viking). I’ve since had the trim tab removed and am running without the tab while I wait ~90 days for a replacement from Bennett. 

On the run home from the yard after having the broken tab removed, i noticed every 10 minutes or so the boat would veer to starboard suddenly, both while under autopilot and manual steering. There was no detectible change in engine noise or RPM (neither of the engines “revv’d up”). I watched this closely as my first thought was that a clutch was slipping. 

So…my thought was this slippage was a result of the missing trim tab, even though the other tab is in the stowed position. There is a pocket in the hull and transom where the tabs are stowed and my theory is that the differential lift with between the side with the tab and without the tab was causing some sort of imbalance.

But i’m really concerned, since the cooler is already leaking, maybe i indeed have a failing oil cooler.

I haven’t seen any signs of contamination in the oil or oil in the exhaust. 

The port cooler is the one that is leaking; the “veering” is to starboard. The starboard side has the missing trib tab.

On to my question – what is actually happening when a failing cooler causes a twin engine boat to “veer”? Is it a matter of briefly losing gear oil pressure that causes the slip? Shouldn’t I see or hear some sort of change in the engine RPM as the clutches slip? If its a failing port cooler, shouldn’t the boat also veer to port if it loses pressure due to the port prop losing power and the starboard prop pushing harder? 

The oil cooler is $9k to replace with the OEM cooler from ZF. Hopefully, if i have to replace it, sbmar can come to the rescue with a matching aftermarket option… 

Topic

[Nicholas]

solved

I was able to source a used OEM cooler. Appreciate the offer to help, may take you up on it when the other one inevitably goes bad 😉

[Nicholas]

Heck you’re practically next door! Enjoy the vacation and appreciate the suggestion. I had asked around and didn’t find anyone willing/able to fabricate it. I do have the old cooler to send. Any sense of how much it would save me vs the $9k OEM option? <br /><br />

Happy to discuss on the phone but don’t want to bother you on vacation (any more than I already have)

[Tony Athens]

Another long term solution:  

“Adapting a different a more conventional external high quality cooler that uses hoses is doable but would require a very clever /good machinist that thinks out of the box and understand boats/marine transmissions.”

 

I get back from a vacay in zip 34448  Nov 2.. I could do this mid-Nov  if you cannot sort it out in your area. You’d have to  send me your cooler to do  it though.      

[Nicholas]

gear cooler is shot

Thanks for the recommendation on Dallas Coolers. Jerry has been great to work with. Unfortunately the cooler is shot. Failed the pressure test. He tried to fix it but said its just leaking in too many places. He said he doesn’t have/can’t make anything that matches it. 

Any other suggestions beyond just biting the bullet and ordering a $9k replacement from ZF? 

[Tony Athens]

Simple to remove.. looks like 3 external bolts.. All the oil flow connections are internal and have o-ring seals, The entire oil cooler just pulls out. Other the the oil in the cooler, nothing to drain– Should not be too messy..

Adapting a different a more conventional external high quality cooler that uses hoses is  doable but would require a very clever /good machinist that thinks out of the box and understand boats/marine transmissions. 

Your gear box is obsolete and to replace it would be in the 30K range plus a big time  labor / other costs.

[Nicholas]

Thank you Tony!<br /><br />Question – how would the cooler oil inlet/outlet be connected? When I look at the parts diagram, it just shows rigid tubes on either end of the cooler extending to the gearbox with a single o-ring. I don’t think it’s a face seal because there doesn’t appear to be any sort of flange. (Pic of parts diagram attached)

also – do I need to drain the gearbox oil to remove the cooler or is the gearbox oil level likely below the cooler when it’s sitting unpressurized?

[Tony Athens]

Old BW ZF165 Issues

Is seems like maybe one set of clutches may be slipping..

If the port gear slips, the vessel with tend to to turn to PORT.

Starboard is the same-If it slips, the vessel will tend to turn to starboard. 

Pull the cooler and send to the Dallas Coolers in Texas–They are the best of the best for repairing/rebuilding  anything like this.

[Author]

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