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Yanmar ZT370 all kinds of problems

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rafnar

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so these last 2 weeks i have been working on two identical rib boats for a whale watching company in Iceland, they each have two Yanmar 6LPA-STZP2 engines and ZT370 stern drives and the problems with these drives seem to be endless, 5 drives are already broken and just sit in the company garage, one of them bought new from the dealer lasted 3 days until it broke so it was sent to the dealer and they sent it back saying it was "unfixable" whatever that means, as far as i know they have always been lubricated properly with the recommended oil as specified in the manual, so im hoping to get some answers here, what can i tell the captains to do in order to lengthen the lives of these drives or are these drives just really bad and should i pitch them the idea to get mercruisers drives, and if so how much work would there be involved in swapping to those drives. And one other thing, i installed a brand new drive on one of the boats two days ago and it went smooth, really nothing that can go too wrong, checked the alignment of the engine beforehand and the drive went into the splines easily with all seals seated properly and all bolts torqued as specified, but when it shifts in i hear a loud knocking noise, only when shifting in, forward or reverse, otherwise its fine, Any ideas?
 
I dont know the yanmar drives but I do know the mercruiser drives. They probably wont last much longer unless they are treated very kindly. The issues with the mercruiser drives and maybe eith your yanmar drives is top much torque loading. On the merc drives they overheat the oil and typically the top gearbox gets too hot and fails.
On the merc drives people install drive showers to help cool the top gearbox. That can help. How are your yanmar drives propped? Can you reach full wot rpms with a full load on, or only when the boat is light? One way to reduce the torque loading is to use smaller props. You will have less speed, but if the drives are failing due to overloading there arent many choices.
 
I have a yanmar 8lv 370 with the zt sterndrive. 385 hrs on the motor and the stern drive has failed three times. each time it has lost all forward gears. Once because of a "faulty 'solenoid. next time because of a different solenoid (so I'm told) last time, after a fix and ONE sea trial --- it failed again.
Now seriously considering tipping the whole lot into the sea and installing Volvo.
 
Llewellyn said:
I have a yanmar 8lv 370 with the zt sterndrive. 385 hrs on the motor and the stern drive has failed three times. each time it has lost all forward gears. Once because of a "faulty 'solenoid. next time because of a different solenoid (so I'm told) last time, after a fix and ONE sea trial --- it failed again.
Now seriously considering tipping the whole lot into the sea and installing Volvo.
Click to expand...
Did you resolve your problems with theses drives?
 
Llewellyn said:
I have a yanmar 8lv 370 with the zt sterndrive. 385 hrs on the motor and the stern drive has failed three times. each time it has lost all forward gears. Once because of a "faulty 'solenoid. next time because of a different solenoid (so I'm told) last time, after a fix and ONE sea trial --- it failed again.
Now seriously considering tipping the whole lot into the sea and installing Volvo.
Click to expand...
Interesting and sad to read. I have twin instalation. Runs 800h and then issues started. However now trying to fix and opened the drive. Could shear findings and info. U can write me [email protected]
 
rafnar said:
so these last 2 weeks i have been working on two identical rib boats for a whale watching company in Iceland, they each have two Yanmar 6LPA-STZP2 engines and ZT370 stern drives and the problems with these drives seem to be endless, 5 drives are already broken and just sit in the company garage, one of them bought new from the dealer lasted 3 days until it broke so it was sent to the dealer and they sent it back saying it was "unfixable" whatever that means, as far as i know they have always been lubricated properly with the recommended oil as specified in the manual, so im hoping to get some answers here, what can i tell the captains to do in order to lengthen the lives of these drives or are these drives just really bad and should i pitch them the idea to get mercruisers drives, and if so how much work would there be involved in swapping to those drives. And one other thing, i installed a brand new drive on one of the boats two days ago and it went smooth, really nothing that can go too wrong, checked the alignment of the engine beforehand and the drive went into the splines easily with all seals seated properly and all bolts torqued as specified, but when it shifts in i hear a loud knocking noise, only when shifting in, forward or reverse, otherwise its fine, Any ideas?
Click to expand...
I will throw some ideas on the table - lower gear vertical shaft free travel. On power engagement the gears are pushed outside each other. Shiming of lower gear is solid and all good. But in my case the vertical shaft has ... 2mm vertical travel play. That compromises "gear back lash" measurments. I am in a process to OH lower unit and find all things that are wrong. Somehow i feel vertical shaft has issues with shiming (my case) and 2ea conical bearings are.... mooving or something. Planing to shoot video
 
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