I have an 89 Supra Mariah. This is a inboard ski boat. It has a reverse rotation PCM 351 engine and a PCM tranny. In the several months since I bought the boat I have discovered lots of minor problems, and a couple major ones. And I am still discovering more. You can see some of my previous threads.
Anyway, I finally got the boat on the water on friday. Boat seemed to run ok, although it seems like it is running rich. One thing that was very odd was the tach. The tach seemed to barely register any RPMs. At idle it showed no RPMs. When we were up and skiing, it was showing less than 1700 rpms.
How fast were we going? Hard to tell, only one of the airguide speedos was working, and it iks probably way out of adjustment.
So I got thinking that maybe the tach was half right-- and perhaps it was set wrong. Maybe set for a 4 cylinder engine instead of an 8. It seemed like a possibility anyway.
So I pulled the tach out of the dash today and found that it appears to be set correctly----the little switch is pointed to 8.
This is a pretty standard VDO tach BTW, it looks like the ones they still make.
So, is a there something that could make tach be off by so much? Do they actually go bad like that? How could I find out?
Thanks
Jared
I guess there is always a possibility, given the unknown history of this boat, that the engine is really running at such low RPMS. But I kind of doubt it. I don't think you could ski behind such a boat-- no matter how it was proped.
Anyway, I finally got the boat on the water on friday. Boat seemed to run ok, although it seems like it is running rich. One thing that was very odd was the tach. The tach seemed to barely register any RPMs. At idle it showed no RPMs. When we were up and skiing, it was showing less than 1700 rpms.
How fast were we going? Hard to tell, only one of the airguide speedos was working, and it iks probably way out of adjustment.
So I got thinking that maybe the tach was half right-- and perhaps it was set wrong. Maybe set for a 4 cylinder engine instead of an 8. It seemed like a possibility anyway.
So I pulled the tach out of the dash today and found that it appears to be set correctly----the little switch is pointed to 8.
This is a pretty standard VDO tach BTW, it looks like the ones they still make.
So, is a there something that could make tach be off by so much? Do they actually go bad like that? How could I find out?
Thanks
Jared
I guess there is always a possibility, given the unknown history of this boat, that the engine is really running at such low RPMS. But I kind of doubt it. I don't think you could ski behind such a boat-- no matter how it was proped.