yamaha questions to ease my mind.

**Don Dieago** · 10-22-2018, 05:26 PM

1986 prov150J

First replaced old omc tach with brand new yamaha with oil one off ebay omc tack work fine put power to yellow and green to signal and black grd and no work. Im sure bad tach bit humor me. set on 12 old tach showed 5400 at 54-55 mph and merc 23 mirage plus prop. this boat is so dang heavy in stern this works best I think.

second Running like top now and wot timing set to 24 degrees can I get away with bumping up to 26-28 on 87 pump?
I dont think I could hear detonation on two stroke at 5500 if I tried! also will the old pro's in good shape live if proped at 5800-6000 rpm?
when replacing head gaskets i found it has wiseco .020 overs and bores look damn good.
man this thing runs so smooth with new reeds and cages lapped. I'm stoked.

**Merc 2.5** · 10-23-2018, 08:20 AM

I wanna answer ur questions but I'm not familiar with yammy. But I wouldn't go that hi with the timing, 6k rpm would definitely b better than 5500 and still last. The yammy guys will chime n soon. Carb motor?

**Markus** · 10-23-2018, 01:03 PM

Originally Posted by Don Dieago

Running like top now and wot timing set to 24 degrees can I get away with bumping up to 26-28 on 87 pump?

I think Wayne Taylor ran them at 27 degrees for drag racing, but 24 is already a lot. I never saw any gains above 21 or 22 from what I remember. I would keep it at 24.

Originally Posted by Don Dieago

also will the old pro's in good shape live if proped at 5800-6000 rpm?

That's where it will live the longest. If propped for too low max rpm, the wrist pins will eat into the pistons.

**Don Dieago** · 10-23-2018, 06:24 PM

Originally Posted by Markus

I think Wayne Taylor ran them at 27 degrees for drag racing, but 24 is already a lot. I never saw any gains above 21 or 22 from what I remember. I would keep it at 24.

That's where it will live the longest. If propped for too low max rpm, the wrist pins will eat into the pistons.

Thank You sir!