Tachometer on a Yanmar 3GM30FC with saildrive

[scaarup]

Hi fellow sailors.

I have a Yanmar 3GM30FC engine with an SD20 saildrive. I have no tachometer but would like to install one. I have made some investigations and I would like to know if it is possible to replace the bolt (marked on the attached picture) with a sender unit (part no. 128170-91160)?

Thanks in advance.

[sailormed]

No idea about the bolt, but why don’t you try it with the alternator output?

[scaarup]

Originally Posted by sailormed

No idea about the bolt, but why don’t you try it with the alternator output?

The manual states, that the tachometer sender is supposed to sit on top of the flywheel, so I guess that is the approach I should be taking as well?

[sailormed]

Well then best approach is to unbolt it and investigate available space.

[scaarup]

Originally Posted by sailormed

Well then best approach is to unbolt it and investigate available space.

Yeah well, the reason why I am asking here, is because I am hoping someone can confirm this approach before I take things apart and order new parts etc.

[Wotname]

I'm 99.9% sure that is the correct spot to fit the tach sender on the Yanmar GM series.

[Wotname]

Just checked the 3GM30 service manual and I am now 100% sure. Pull the bolt and confirm it is a M18 thread - the tach sender uses a M18 thread and 24mm AF spanner (wrench).

[GordMay]

Greetings and welcome aboard the CF, scaarup.

[Wotname]

Interesting Gordmay, your attachment shows a 3/4 x 16 thread on the sender but all the Yanmar tach senders of this vintage have been M18 x 1.5. I wonder if Yanmar made a special run for the north American market.
???????????????

[scaarup]

Originally Posted by Wotname

Just checked the 3GM30 service manual and I am now 100% sure. Pull the bolt and confirm it is a M18 thread - the tach sender uses a M18 thread and 24mm AF spanner (wrench).

Awesome - thank you.

Now I am just wondering what this "backplane" (highlighted on picture) is. Seems like the bolt is holding that, and when I look at pictures of 3GM30 without saildrives, this "backplane" is not present (example picture attached).

[Wotname]

Originally Posted by scaarup

Awesome - thank you.

Now I am just wondering what this "backplane" (highlighted on picture) is. Seems like the bolt is holding that, and when I look at pictures of 3GM30 without saildrives, this "backplane" is not present (example picture attached).

Hmm...
Here is the drawing from my 3GM30 manual and it looks just like yours.

I wonder if the other picture is of an early 3GM30 or even a 3GM.

[scaarup]

Originally Posted by Wotname

Hmm...
Here is the drawing from my 3GM30 manual and it looks just like yours.

I wonder if the other picture is of an early 3GM30 or even a 3GM.

That is a good point . I found it here, and it actually only says "3GM30" - https://www.inautia.com/boat-accesso...968504548.html

[GordMay]

Originally Posted by Wotname

Interesting Gordmay, your attachment shows a 3/4 x 16 thread on the sender but all the Yanmar tach senders of this vintage have been M18 x 1.5. I wonder if Yanmar made a special run for the north American market.
???????????????

I uploaded that dwg over a decade ago, & don't recall, for certain; but I suspect that it was from a Teleflex document.

[bigdogandy]

Originally Posted by scaarup

Hi fellow sailors.

I have a Yanmar 3GM30FC engine with an SD20 saildrive. I have no tachometer but would like to install one. I have made some investigations and I would like to know if it is possible to replace the bolt (marked on the attached picture) with a sender unit (part no. 128170-91160)?

Thanks in advance.

Have you tried contacting your local Yanmar parts supplier? He should be able to use your engine serial number to look up exactly what you need.

[scaarup]

Originally Posted by bigdogandy

Have you tried contacting your local Yanmar parts supplier? He should be able to use your engine serial number to look up exactly what you need.

I have yes, but no reply yet. Will post it here once I get one. Anyway, the knowledge and experience in this forum, is not to be underestimated.