"engine sync" on or off?

[FrankM]

215 Twin engines. In my settings menu I have the option to turn "engine sync" on or off. I know what this is doing. My question is under which circumstances I want sync off and when do I want sync on? Or always leave sync on?

 

[WaveJunkie]

Thought your supposed to run both as water will enter the one that is not running.

 

[FrankM]

Thought your supposed to run both as water will enter the one that is not running.

Both engines are on. If you turn "sync" on the computer tries to sync their rpm. If "off" they are slightly different.
My brain says "keep always on". But why do I have the option to turn it off? Do I ever want to turn it off?

 

[WaveJunkie]

Do you have a key for each engine?
The only time I could fatham would be if one isn't running properly.

 

[FrankM]

I have a 2019 215. 1 key and 2 start buttons.

 

[Joatmon]

I would think "un syncing" would put an undue stress on one engine. Now, this may be necessary. I had to come in with only one engine due to a pump locking so tight the engine would not run. No issues with water entering the off engine. I saw no evidence that it did anyway. With the Scarab closed water cooling system it shouldn't be an issue using one engine. It got me back to the dock.

 

[MD23679]

I would think "un syncing" would put an undue stress on one engine. Now, this may be necessary. I had to come in with only one engine due to a pump locking so tight the engine would not run. No issues with water entering the off engine. I saw no evidence that it did anyway. With the Scarab closed water cooling system it shouldn't be an issue using one engine. It got me back to the dock.

NEVER RUN THE BOAT MORE THAN 5 MPH WITH ONE ENGINE OFF !!! IT CAN BACK UP INTO THE EXHAUST PORTS OF THE ENGINE AND FILL THE CYLINDERS WITH WATER AND THAT WILL HYDROLOCK IT. JUST USE WHAT I DO AND YOU'LL BE SAFE ... $15 WOULD SAFE YOU THOUSANDS OF DOLLARS ... ON-OFF VALVE ON THE INLET HOSE WOULD DO THE JOB .

 

[Joatmon]

NEVER RUN THE BOAT MORE THAN 5 MPH WITH ONE ENGINE OFF !!! IT CAN BACK UP INTO THE EXHAUST PORTS OF THE ENGINE AND FILL THE CYLINDERS WITH WATER AND THAT WILL HYDROLOCK IT. JUST USE WHAT I DO AND YOU'LL BE SAFE ... $15 WOULD SAFE YOU THOUSANDS OF DOLLARS ... ON-OFF VALVE ON THE INLET HOSE WOULD DO THE JOB .

It has been a few months and I thought about what you said again. At first I did not fully understand how water would get in the engine cylinder so I took what you said and did some research. As you already know you were correct. In the Rotax service manual it addresses towing the boat and pinching off the water lines. This would be the same as only running one engine. My next project is to install the valves as you did. The pinch tools would work but not as easy to use and not as reliable as the valve. Thanks.

 

[FiftyYardFistFight]

Both engines are on. If you turn "sync" on the computer tries to sync their rpm. If "off" they are slightly different.
My brain says "keep always on". But why do I have the option to turn it off? Do I ever want to turn it off?

I would turn it off only if one engine were not operating properly, say if one failed, or worked but at reduced RPM. In this case you don't want the good engine reducing power to match the bad one. Say you sucked up weeds or a rock on one side. That engine can idle or operate at reduced thrust. It still provides alternator charge and won't fill with water. Turn off the sync and head home.

 

[MD23679]

I would turn it off only if one engine were not operating properly, say if one failed, or worked but at reduced RPM. In this case you don't want the good engine reducing power to match the bad one. Say you sucked up weeds or a rock on one side. That engine can idle or operate at reduced thrust. It still provides alternator charge and won't fill with water. Turn off the sync and head home.

You could always turn off the sync ... install the valves and enjoy boating .

 

[MD23679]

It has been a few months and I thought about what you said again. At first I did not fully understand how water would get in the engine cylinder so I took what you said and did some research. As you already know you were correct. In the Rotax service manual it addresses towing the boat and pinching off the water lines. This would be the same as only running one engine. My next project is to install the valves as you did. The pinch tools would work but not as easy to use and not as reliable as the valve. Thanks.

View attachment 221255

My pleasure

 

[Joatmon]

My pleasure

Well as I told you I had planned on installing the valves, but when I went to actually do the work I stopped because I have questions.

The Rotax manual view for my 150hp cat engines appears to show the 1" hose I need to cut and insert valve goes into the front of the exhaust manifold on right side of engine. I assume the manifold has a water cooled jacket and in no way connected to the closed loop engine coolant system. This does not sense to me. If water can get into the cylinder through the fresh water jet pump intake via the jacketed exhaust manifold when towed and engine is not running and engine is cooled closed loop then how is this possible?

Am I looking at the wrong hose and is there another hose I am not seeing? If this is the right hose it is going to be a challenge to access, cut and route the additional hose and valve. And you even made valve mounts. Impressive!

 

[MD23679]

Well as I told you I had planned on installing the valves, but when I went to actually do the work I stopped because I have questions.

The Rotax manual view for my 150hp cat engines appears to show the 1" hose I need to cut and insert valve goes into the front of the exhaust manifold on right side of engine. I assume the manifold has a water cooled jacket and in no way connected to the closed loop engine coolant system. This does not sense to me. If water can get into the cylinder through the fresh water jet pump intake via the jacketed exhaust manifold when towed and engine is not running and engine is cooled closed loop then how is this possible?

Am I looking at the wrong hose and is there another hose I am not seeing? If this is the right hose it is going to be a challenge to access, cut and route the additional hose and valve. And you even made valve mounts. Impressive!

View attachment 221395

A couple of months ago , I saw someone towing his jetboat , scarab 255 wake edition. He was towing it at 25mph , which is fast. Days later , i saw the same jetboat at the workshop where i serviced my engines. HYDROLOCKED his engines .

I'll take pictures and post them here next month. For now , just keep clamps on board if you need them.

Amazon.com

 

[Joatmon]

Thanks for the info. I believe what you are saying but being an engineer I have to understand why. I will dig deeper to see if I can understand how this happens.

The engine is cooled in a closed loop system and the exhaust manifold is cooled using lake/ocean water via a jet pump intake. For water to get into the engine block when being towed the lake/ocean water has to be forced into the engine exhaust manifolds then forced into the cylinders via the exhaust valves. This means the jet pump and or scoop intake where the exhaust cooling water exits when the engine is running is THE source of the water getting into the engine as you said.

I’m going to see where the water enters and exits the exhaust manifold at the pumps. I’ve had the pumps off for rebuild but I never noticed the intake and exhaust water ports.

Thanks again.
.

 

[MD23679]

Thanks for the info. I believe what you are saying but being an engineer I have to understand why. I will dig deeper to see if I can understand how this happens.

The engine is cooled in a closed loop system and the exhaust manifold is cooled using lake/ocean water via a jet pump intake. For water to get into the engine block when being towed the lake/ocean water has to be forced into the engine exhaust manifolds then forced into the cylinders via the exhaust valves. This means the jet pump and or scoop intake where the exhaust cooling water exits when the engine is running is THE source of the water getting into the engine as you said.

I’m going to see where the water enters and exits the exhaust manifold at the pumps. I’ve had the pumps off for rebuild but I never noticed the intake and exhaust water ports.

Thanks again.
.

Thank you and likewise , we learn from each other on this forum. Water pressure will eventually get into the cylinders .

https://www.crowleymarine.com/d/tech_article/service-manual-jp-aa-rotax-1503-4-tec-150-200-250-hp-service-manual-p-n-460660---shop-manual-maintenance-special-procedures-0460660