I'll get the prop, hub, and plugs tomorrow so the fun will begin. Turns out it had NGK BPZ8HS-10 resisistor plug in it so I have the proper Champions coming. It will be interesting to see if that makes a difference.
My background is mostly sailboats but have owned a number of power boats over the years. Some of them I've only kept for a week they irritated me so badly and I never found one that I really liked until I stumbled onto Seacrafts. I one ride took in my Tracker SF 20 and that was it, I finally found a power boat that I liked lol! This 18 will become my daughter's boat next year and hopefully she hands it down to her kids someday. I then have four more to work my way through, not really sure what I was thinking:confused:

Glad you're looking at the spark plugs… that was my initial thought tied to the ignition. I have successfully converted my father to an 18 seacraft from being a lifelong sailor. The 80's tracker boats get little respect, which is fine because it allows for a greater population of newer boats to buy. They are great SC's for the most part.

Its the ride and the sound. A sailboat hull and SeaCraft hull doesn't pound and makes the same sound cutting through the waves...swoosh,swoosh,swoosh

Got the proper plugs installed, it definitely idles and runs smoother in general. Didn't make any difference dramatic at higher rpms but the tach is definitely trashed. Today it was stuck on zero and then started hopping all over the place lol! As soon as the rain stops I'll get the prop installed and see what that does.
@76Red18, you are 100% correct about the similarity in hull motion between a Seacraft and a sailboat, both are just a pleasure to be on regardless of conditions.
Got a chance to try the 4 blade Apollo this afternoon and I have to say I think it is a big improvement. Hole shot time is cut in half, no loss in top speed and maintains plane down to 14 mph. Hard to tell rpms as the tach is all over the place, it read 5500 rpms at one point. :)

The NGKs have blown more power packs than I can count. Also affects rectifiers/regulators and OIS. Not sure about your motah but my rude 96 150 had the same issues.
When I got it 9 years ago the tach was all over the place, Champs and a new to me tach fixed her.

Recently had the tach drop out and pulled the rectifier. Melted a tad. Easy fix and a new tach. Happiness. One of the reasons I love omc old tech is parts are everywhere and cheap in boat dollars.

Now the exchange rate for currency varies a lot. Lots of folks love their Yammis and that is fine, but the exchange rate is ridiculous.

2k for a powerpack???

It is clear to me that Yammi wants you to be on the fence. New 4 st vs old OX 2 st.`
Do I spend that or consider new???.

Now a power pack for a rude is still more than it should be, but under 300 is a far cry from 2k. This is factory not CDI. As for cdi, some folks have luck with them, but I`ll pass.

Get a gasket for the rectifier and pull it off? Melty? If your volts are running high and tach
is dancing or cutting?

Thanks for all that info and will certainly check the rectifier out. I do have some other tachs so will do some swapping out. This will be my daughter's boat next year so it needs to be as reliable as possible. Thanks!
Rod

GFS is more poetic than I, but I just did a rectifier myself....one of the 1st signs of a bad rectifier is the tach jumping. Still sounds like ignition issues. I am currently working on loose flywheel magnets and Checking the stator.

Tach was reading 0 when the motor was at a fast idle then stayed at 1k when it was off. Seems like it just worn out but who knows, I'll swap it out and see where that goes. Always an adventure :)

Clean ALL traces of grease and corrosion off of ALL terminals, fine pin plugs, etc..DO NOT apply anything of any type on those fine pin plugs. Replace any wing nuts on your battery terminals with lock nuts. Very important things to do before you spend any money on ignition parts. There's a cylinder # switch on the back of your tach. Switch that back and forth a few times making sure you you set it for a 4 cylinder. Pretty sure thats what your 120 is.

Aside from the tach issues, my gut feel is that a 13-¾" x 15 is the right prop for that motor and hull.