Re: tach installation?
I have the Tohatsu/Nissan factory tach installed on my 9.8. I also have an aftermarket hour meter. The motor is an EP model: electric start and remote control. The RC for the 9.8 does not have a low oil pressure warning buzzer, so there was no way to get a remote low oil pressure indicator without some sort of additional remote setup.
The oil light is very important in my installation, because the outboard lives in a well in the lazarette of my sailboat, under a hatch. Essentially, it's an inboard-mounted OB. The factory tach I chose has the oil pressure light -- it's also available sans light, if one would want that for some reason. Yes, I suppose I could've removed the led from the cowling and relocated it, but this way, I haven't mangled the factory light wiring setup. As a Tohatsu dealer, I don't want to display a Frankenstein setup for my customers to see.
The factory tach is pricey, as TG noted. A tiny-tach would have been cheaper, but it doesn't have the oil light, which was the primary reason I went with the factory unit. Running without oil pressure would be a lot more expensive! If you get the factory tach, I would also recommend getting the factory wiring for it (two separate cable assemblies, includes instrument night lighting). Makes installation a snap, since it uses the correct color codes.
The hour meter was affordable, but I had to shop around. Some of the hour meters are quite expensive for some reason, even though they appear to be made in the same factories. The tach was a good investment. For instance, since I have an ammeter on the boat, I can determine at what RPM the OB's alternator overcomes various electrical loads. The hour meter is great for logbook entries relating to the motor, such as scheduled oil changes. Those records keep me in warranty compliance. Quite nice.
But, it can be done...I would check with Tiny Tach for a cheap tach that works off of induction rather the OEM factory models we sell for far more than what a sane person would pay. Did I just say that?