TurbosRfun

Just picked up a 454/330HP Bravo1 Sunsation Rocket and I have some questions and am looking for some help and suggestions if any of you have a little time. You all may just tell me to get a service manual for the engine and drive... which is fine, but where would I get those?

I have experience with swapping motors in cars (mostly newer stuff, foreign), so I'm not a mechanical idiot... but I don't know old school American motors very well, and not much at all about outdrives, transoms and boat things like that.

The boat has ~430 hours on it now.

1.) What kind of speed should I see with this boat? It seems that I get ~63mph with 4 people and half a tank of gas on 1-1.5 foot chop. I can get about 4700RPMs with it, but I have to "trim up" to get it. I think I'm cavitating a bit to get that RPM... if I trim down a bit, I turn about 4200-4300 RPMs and a couple less MPH.

2.) How easy should it be to turn the prop with your hand when on a trailer? It seems that it has gotten a little harder to turn than when I first got the boat (could just be me). I was going to change the outdrive fluid (don't know if there's different fluid for different parts of the drive or what) but I don't see any clearly visible drain plugs on the lower section anywhere.

3.) Any performance mods that can be done for low to moderate prices??? Would it be better just to swap in an EFI 496 or something??? What's required for such a swap?

Questions like these. I have a feeling that I will be making posts for questions as I go along, but if anyone can help me out that would be really nice.

Thanks in advance,

-=Mike G.

Knot 4 Me

1.) What kind of speed should I see with this boat? It seems that I get ~63mph with 4 people and half a tank of gas on 1-1.5 foot chop. I can get about 4700RPMs with it, but I have to "trim up" to get it. I think I'm cavitating a bit to get that RPM... if I trim down a bit, I turn about 4200-4300 RPMs and a couple less MPH. Grab a handheld GPS and take the boat out with a buddy. Trim the boat until you feel it start to slip (you will be gaining RPM but losing or holding steady on speed) and then trim back down slightly until it bites again. Post back what that GPS speed and RPMs are. You cannot trust the speedometer as they are all inaccurate. Also, post what type prop you are running (3 blade, 4 blade) and what the prop's pitch is. You should be turning no more than 4,600 RPM at WOT.
2.) How easy should it be to turn the prop with your hand when on a trailer? It seems that it has gotten a little harder to turn than when I first got the boat (could just be me). I was going to change the outdrive fluid (don't know if there's different fluid for different parts of the drive or what) but I don't see any clearly visible drain plugs on the lower section anywhere. It should be fairly easily turned by hand. The drain plug on the lower unit is located just below the propshaft. You have to remove the prop to access it. You should also see the vent plug located on the upper part of the drive on the starboard side. If you change the gear lube, it is a good idea to have the fiber gaskets on hand in case the old ones are not reusable. Use either Merc High Performance Gear Lube or a quality 75W-90 synthetic gear lube such as Mobil 1, Royal Purple, etc. Capacity is about 2.8 quarts.
3.) Any performance mods that can be done for low to moderate prices??? Would it be better just to swap in an EFI 496 or something??? What's required for such a swap?You have to get into the heads and camshaft to make any appreciable performance gains with this motor. You are better off starting from a better base such as a 454 MAG, 502 MAG, HP500, etc. You cannot drop in an automotive motor as is and run it in a boat. Camshaft profiles and valve materials are not proper for a marine application.

johnny b good

You can also call the guys at Sunsation they are a very customer friendly company.

TurbosRfun

Hey Knot, thanks for the response. I think I have some other problems to attend to now before increasing performance. I will be bringing my GPS out next time, but for now see below:


Something's up with my drive I think. Boat did ~64mph at ~4600RPM and cruised at ~39-40mph@3000RPMs (with only me in the boat). Now, 4 trips out on the lake later, I'm getting ~28mph@3100RPMs and ~48MPH@Full throttle which is only like 3900RPM now. Something is definetly wrong. Noticed that there's a resevoir in the back that says "Automatic Transmission fluid only" that is WAY below the add line... wonder if that's the cause of my problems. The warning buzzer went off the last two times I went out. I didn't think that I had a transmission in my boat, but I could be wrong for sure... still learning about boating.

-=Mike G

TurbosRfun

OH... and the prop. still turns by hand like it did when I first got the boat. It'll get about 2/3 a rotation after I spin it by hand.

-=Mike

Inspector

Ouch! With that large a loss of speed you better start looking at the engine. Do your oil pressure and water temp gauges work? The engine alarm is for low oil pressure or hi water temps. The 330 HP engine is... well... kind of the station wagon engine of the boating world. It has cast internal components and a mild enough camshaft that it usually won't go fast enough to hurt itself. But as with any mechanical item, it will wear out eventually. Good luck...
Also, if you like turbos, I have some Gale Banks BBC twin turbo set ups I may be willing to part with if you choose to build an engine.