AWOL

Went down to the boat and cleaned it up. While down there, I took out some plugs to just take a look.

Port Motor, Cylinder 1:

Port Motor, Cylinder 5:

Starboard, Cylinder 4:

Starboard, Cylinder 6:

AWOL

BUMP

Ran the boat tonight. Pretty hot out here in Buffalo @ 82 degrees and humid.

The boat has Thunderbolt IV V820R ignition modules and the base timing was only set to 10 degrees. Bumped it up to 34 total advance and settles at ~14 at idle. Ran the boat with the labbed Bravo 1 28P props. It spun them to 5200 rpm all trimmed out, just me, and both gas tanks around 5/8 full. Hit 77mph on gps, which gives me a prop slip of ~16%. Thats high for my liking.

Ive got a set of (stock) bravo 1 26P I am going to try, hopefully get the slip down and rpm up or close to the same, which should get me a mph or 2 more.

I also talked to the engine builder and he thinks these should be putting out 550+ HP, closer to 600HP. He thinks the 800CFM carb is on the small side.

Still havent messed with the jets yet. The boat did not run any faster with the hatch up.

SB

iTrader: (1)

You running race plugs ? By that pic it looks like your ground straps are 'cut back' away from the elctrode vs terminating over the electrode like a conventional plug..

I'm not sure if the Tbolt ign system has enough uice for those at higher rpm. When I say I'm not sure, I am not sure, but it raises some flags in my head. Anybody else successful with these without a big juice ignition system ?

AWOL

AWOL

BUMP part 2

Ran the 26P Bravos, was spinning 5500 and hit 80.3 - which is too much RPM. Went back to the 28s, and put in some new V822 Thunderbolt IV ignition modules with the more aggressive advance curve. Re-adjusted the timing for the new advance total so Im ~ 35 @ 3500 RPM and the boat went 83.5 on GPS with half tanks and 1 other person.

I think she's as dialed in for now and will now work on the exterior paint scheme.

I think these motors are finally in the 500-520hp area.

AWOL

Just an update on this. Ended up trying a variety of props this summer (24 (came on the boat), 26, 28, 30 bravo 1s and Mirage Plus 3 blades) and decided to keep the labbed 28s and Mirage Plus' that were repitched to ~29.5.

Re-timed the motors to 36 degrees total, started running straight 93 octane, and got more air into the motors via NACA ducts and more air out via venting out of the back hatch. Sanded the lowers/skeg, and plugged the holes left from the drive showers. I also removed the pitot tube dragging behind the transom. I left the jetting the same, as the plugs lightened up some after these adjustments and appear to be where they should be. I may switch back to stock plugs, just to get that last variable taken out. Trimming to ~ 8/8.5 on the indicator is ideal for max speed.

Mirage 3 blades are a little faster and much better cruise than the labbed 28 bravo 1s, but a pain to get on plane.

hogie roll

Tinkerer

Did you try bigger flame arrestors?
great job on getting it where it is.
You can modify the drives for more negative trim so that you can get on plane with the three blades.

AWOL

I did not try bigger flame arrestors yet. I had a lead on some from a Mercury racing 600, but opted not to buy them. There are height issues with the hatch. I was going to maybe try and remove the lining from the arrestor first as an experiment.

This was my work-around for the time being:



The 3 blades Im going to keep for exclusively chasing high speed runs. The Bravos were a little slower in top speed and 5-7 mph in cruise, but planing was amazing and running with 5-6 people on board and full gear - its the right prop.

This summer was great and the boat had 0 issues.