WOT speed on a '83 20' SF w/200

[spareparts]

the specs i wrote came right out of the Mercury manual for 99. i have never swaped carbs around other than swapping complete sets, like i said, it would take a dyno and a lot of time and money to figure it all out, looks like the guys at scream and fly have spent the time and money( cool site).

I keep coming up with more ideas as the day goes on, does your boat have trim tabs? If so are they mounted flush with the bottom. Years ago I had a customer with a 60 mph boat that wanted tabs put on it, i installed the tabs per the instructions, mounted flush with the botom, with the trailing edge 1" up in the full retracted position, he lost 6 mph. Not the first time someone spent money and slowed down. I had to repair the holes for the tabs and cylinders, move everything up 3/4 inch, remount it. He picked his 6 mph back up, and got the chine walk under controll. The tabs mounted flush efective increased the wetted surface, without a clean break at the transom, it actually sucked the back of the boat down( you would think it would lift the bow).

[Blue_Heron]

Bigshrimpin,
Yeah, most of what I know about Merc carbs, I got off of Scream & Fly. S&F was also where I found out about the timing module (idle stabilizer)on some models acting as a rev limiter. I disconnected it on my XR4 and it jumped from 5600 WOT to 6200. I repropped it and got it back down to 5800. Picked up about 6 mph top end and still have good hole shot. It's a great forum, but like any , it's sometimes hard to tell who knows what they're talking about and who doesn't.

I'm with you on the boat budget. With two boats, there's only so much the Mrs. will tolerate. I just threw five bills at the trailer under the Action Craft yesterday; new tires, hubs, axle, springs and associated hardware. Would have been at least seven if I hadn't done the work myself. B-O-A-T = break out another thousand.

Spareparts,
Yes, I do have trim tabs. They're mounted flush to the bottom and hard against the outer chine. I think the trailing edge is 5/8" above the plane of the hull bottom. I didn't think about them limiting bow lift, but that makes sense. My action craft had the opposite problem, too light in the bow, and I ended up putting transom wedges on her so I didn't have to drag the trim tabs in the water to keep her from porpoising at low speeds.

The reason I keep going back to timing is that just after I got the boat, I ran it with the 22p prop and got it up to 5500 and 49 mph. I wonder if the timing module had a hiccup and bumped the advance? Performance has dropped off since then. Maybe I just had it very lightly loaded at the time. Anyway, I'm gonna keep playing with it.

Thanks to both of you for your posts. Have a happy Thanksgiving. I'm loadin up the wife and kids and Goin' to visit the in-laws and see if I can put a bullet in ole Bambi.

[Bigshrimpin]

http://www.biggerhammer.net/mercury/

This was posted before a while back, but it's a useful reference.

This is another good site.
http://www.byuboyz.com/

The Cherry 2.4L project.
http://www.byuboyz.com/modules.php?n...warticle&id=45

Good Luck with everything!!