Hot Boat

ran my boat with 425 hp and hit low to mid 60's running a 21 4 blade at 5400 when i first got the boat. It takes 525 hp to run low 70,s in that hull. and 850hp with a shorter drive and extension will hit 90

Hot Boat

What size cam are you running... post the cam specs...where is the cams power band?

You say you have stock manifolds. Are they stock cast iron with stainless risers or aluminum Gil manifolds? Threes big difference. If you would have had the motor dynoed they would of used long tube headers, if you then go and install the stock steel manifolds on you will lose some good hp with out a doubt. Also when they dyno motors they usually don’t use the flame arrestor, bolt that back on and deduct 20 or so hp. So I would think you should deduct about 40+ hp off your estimated hp to the prop.

Where is your timing set? 2 degrees of timing can be a big difference in hp. That’s where the dyno would help to find the most timing advanced you can run with out blowing the motor up.

If you haven’t dynoed the motor I would recommend running a innovate wide band O2 meter and check your air/fuel ratios to make sure you not running lean and on the edge or to rich and losing HP. I run one even after the motor was dynoed, I found once it was in the boat I had to go up 8 jet sizes to get the air/fuel ratios where we wanted them.

What it sound like to me is that you should try and run a 21 3 blade and get the rpms up to 5400 so you can build some more HP. I would think your going to be around 65 mph what puts your motor around 425 hp range. Maybe I'm wrong, but I have had experience with this boat for 10 years and I know what it takes to make it run.

jeff1000man

You said you shaved the heads .030. This raised the comp ratio quite a bit on that engine. With the added comp comes the need to rev the engine higher and you might want to increase the duration of your cam to compensate for the comp increase.

If it was a stock ZZ502 from GM, you should have left it alone. If anything, you lost HP by modifying the deck height on your heads without adjusting the cam to match. You have likely moved your power curve further up the RPM range. If that engine was originally spec'd to turn to 5000, and you raised the comp ratio without a cam adjustment, you will likely see that engine making power up to around 54-5500/

You will have to spend a lot of time testing it to see what it will do, but I would go all the way down to at least a 21P mirage and even try a 19 if you can find one just to see how high the engines is making power, then take all the data that you have gained off of the 3 blade props and call BBlades and have him custom build a prop for that boat.

Good luck

chuckyarus

I think I found my problem. I don't think this guy was trying to screw me I think it is a zz502 short block but It has 119cc square port heads now after I had them shaved .30 there probable around 116cc now. The zz502 500hp from gm came with 110cc oval port heads and was 9.6 to 1 comp. I think thats my problem. I don't have the comp. I thought so I'm probably far from 500hp right now.

Baja226sport

iTrader: (28)

Ever get this figured out? I am looking at buying one of these boats and would like to know how it performs. I even think I saw yours listed for sale on craigslist.....how's run? i might wanna buy it!

TomR

I like Hot Boat have had my boat for 10+ years. It runs just over 80 with about 625hp, "modified" 25 Mirage Plus turning approx 5400.

Rebuilding this winter...........shooting for 85+