View Full Version : Holley carb jetting

09-06-2006, 01:56 PM
I am running my '87 Prostar 190 at a little over 7000 feet. Anybody have recommendation for jetting? The jets in there are 62s. Idle screws almost all the way in and still a little smokey. Also surging at idle. Just bought this poor, neglected little boat and I am trying to get it in running like it should! (351 Motor)

09-10-2006, 09:58 AM
Regarding your carb issues - I've been through this problem a few times, as I am a glutton for punishment and I LOVE old MC boats...

Anyway, after fighting with 20 year old carbs for weeks on end, I finally learned one incontrovertible truth...Carbeurators, especially marine carbs were never meant to last 20+ years. Your problem likely has far less to do with jetting than it does with wear & tear.

So - here's your easiest solution, and in my opinion your only REAL solution. Go down to your local NAPA auto parts store. Have them look up the Holley Marine Carbs in their parts book. They can locate the right 600 or 700 CFM carb for your boat (PCM 351 I presume). They run about $500. (They retail for $700+ at your local MC dealer).

The great thing about NAPA auto parts stores is that they guys in most stores are usually really cool about offering help if you need it. The carb will come with jets for various elevations, and a jetting guide for your elevation range. If you ask, they'll probably help you switch them out right there in the store. I'm at 5,500ft, and after this 5 minute procedure, I took my carb home, put it on my boat, and took it to the lake. It started and ran like a Fuel Injected boat, and has done so ever since...

2 things that are EXTREMELY important:

1. You MUST get a MARINE carb - don't let anyone talk you into a much cheaper Edelbrock for your boat. This is because marine carbs have anti-backfire mechanisms, and are built for marine apps specifically and,
2. Marine applications jet differently because of engine loading. A passenger car isn't constantly under load when you're driving down the road, so a passenger application runs leaner at mid- and high-rpm ranges. Boats are under constant heavy load, and must run richer at mid- and high-rpm ranges.

I know that's a lot of reading, but I just don't want to see anyone fighting with an old carb when a much easier solution is out there...

Good luck,