i have a 24 ft chris-craft with a bravo 1 on back . i just bought boat and ugly weather keeps me fron taking it out for first time . the engine is a 30 over 454 with new turbo pistons in it. my question is : it has the gale banks 330 mercruiser twin turbos on it. when speaking with prev owner who said at 3500 rpm he gets about 6 to 7 lb of boost. boat seems to top out at 68mph. with the cylenders being larger can the boost be raised ? in the instructions i dont see anything about a timing retard box or anything. being new to turbo motors i would rather learn then scatter it . so i come to the pros.. please any help would be great . i e mailed banks turbo and never got back to me . thanks dan :idea:
Unfortunately, Banks no longer offers customer support on their marine turbo systems, even if you try to phone them. I worked for them in the late 70's when the Merc kits were popular. I am pretty sure with that kit you are going to want to leave it stock, with the low boost, particularly since there is no intercooler.
First off the cylinders being larger has nothing to do with boost. You could turn up the boost even if the engine isn't set up to handle it. Boost is a function of either how much the turbo can make or what spring you have in your wastegate. There are ways to get more boost but in return you also have to add more fuel and take away more timing. So just turning up the boost isn't a good idea unless you can also do the other two. The other thing I would recommend is getting a Wide Band O2 meter if you don't have one, they have really come down in price the last couple of years and will really help you get your engine tuned correctly. Then at least if you do turn up your boost you can make sure your aren't soo lean that you will start hurting parts.
hey thanks the info . where can i install the o2 for adequate readings and will the water in exhaust hurt it. is like to understand the fundementals of turbos before i jump head first and land in my pocket book with a broken motor. ill start by getting a o2 guage. where is a good place will cp performance have it or eddie marine. is what i have a decnt system . how can i tell what spring i have to get a idea where im starting from .
The old Banks Merc systems didn't have a wastegate system, unless I am mistaken. They simply had a bypass in the turbo exhaust housing. That Mercruiser system was designed to provide mild boost on a mild ( stock) engine. If you want to make more serious power, you may want to consider going another direction. You still have the stock Merc iron exhaust manifolds, correct?
yes it still has cast manifolds. the turbos seem to be made in cast also . odd to me. i didnt see a wastegate on them at all . i also think it runs good leave it alone. but i love to tinker. is it poss to get anymore out of it without scrapping them all together ?
If you changed exhaust to increase flow, then you would need to reconfigure the system. If you reduced the size of the bypass in the turbo exhaust housing, you will probably have a problem running pump gas, I would think 6-7 lbs is already near the edge for todays pump gasoline in a big heavy boat, with a carbureted system. Why was the engine rebuilt, no burned pistons or valve problems or anything?
hey thanks the info . where can i install the o2 for adequate readings and will the water in exhaust hurt it. is like to understand the fundementals of turbos before i jump head first and land in my pocket book with a broken motor. ill start by getting a o2 guage. where is a good place will cp performance have it or eddie marine. is what i have a decnt system . how can i tell what spring i have to get a idea where im starting from .
At least 6" past the turbine housing and yes water through the exhuast will hurt it, you will have to run dry exhaust while tuning. Then take out the O2 sensor and put the plug in when you are done. About the best one out there right now is the Innovate Motorsports unit for the money anyway. Check out www.tuneyourengine.com, I sell them as well as many people. Sumitt Racing.. I am sure you can find one in your local area.
If this turbo has an internal wastegate or bypass hole you could block it and go with an external wastegate or better yet buy some newer turbos with an internal wastegate.
I guess I need to repeat that the old Banks Merc kit was a kit built for mild boost, mild performance gains on a stock Merc engine. No intercooler, based on stock 330 hp engine with cast iron exhausts, bypass hole in turbo housing, pump gasoline. It's not a real good candidate for upgrading, probably much better off looking for a better setup with better exhaust manifolds, or one of the other early turbo kits from Banks, PFM or Race Aero if you need to keep a tight budget.
engine was rebuilt because of some plug that went bad and aloud wather into cylender and caused to hydro lock. bent rod and scored walls. i took engine to tony otos who is well known in the nascar circuit and he bored block and put all new turbo pistons in it. as it is boat runs good. but i think ill look into the other systems. i have had 6-71 and 8-71 on engines but wow im hooked on turbos now. even with the little i got from these.
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