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twin turbos on 330's super budget build Which turbo's?

Old 02-12-2019, 10:59 PM
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Originally Posted by phughes69
I want to use ebay internal wastegate turbos on my 330's The engines have the larger oval port heads. Im going to mount them to Gil manifolds. I want to do a low boost (5 lbs, maybe 7 lbs) no intercooler. This is mainly for the WOW effect at the dock. Im am thinking that 500 hp is a safe number on the stock blocks. Ive looked at HX35's but not sure if they will even spool at 5psi. Anybody have suggestions from experience. Id like to do internal wastegates so I dont have to deal with that plumbing. This is going in a 1978 30' Scarab.
by 330s i assume you mean HP, so they are 440 cubic inch motors. HX35 will spool on up and probably choke the motor up top. you can easily spool up on of those on a 350

learn how to read a compressor map,
https://www.enginelogics.com/read-a-...ompressor-map/

HX35 will require a rebuild if you are going to do a draw through carb, which brings me to my next point.... EFI. yes there is learning involved by you can dial the setup way better once you learn. plus you get knock sensor that can start to pull timing and get progressive in the timing pull the more times it detect knock.


no intercooler? why?!? you have unlimited cooling potential and you are not going to use it? that's just dumb. plus you are trying to stave off detention

Originally Posted by akattack
Patrick, you don't need wastegates at all for what you are looking to do. The original Merc 475's had a 3/4" hole in the housing to bleed exhaust prior to impeller so you could do the same. The 3/4" hole netted around 3-4 pounds of boost so maybe 1/2 or 5/8" hole would get you 5 pounds. I say go for it, would look really cool when you open the hatches.
awful idea, when did they spool up? use an internal WG and move on. you normally want power thats why one would use a turbo, so you want it spool up ASAP then bleed exhaust energy to control. unless you are trying to delay spool up to protect the stern drives
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Old 02-13-2019, 03:04 PM
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Originally Posted by KeatonAZ
by 330s i assume you mean HP, so they are 440 cubic inch motors. HX35 will spool on up and probably choke the motor up top. you can easily spool up on of those on a 350

learn how to read a compressor map,
https://www.enginelogics.com/read-a-...ompressor-map/

HX35 will require a rebuild if you are going to do a draw through carb, which brings me to my next point.... EFI. yes there is learning involved by you can dial the setup way better once you learn. plus you get knock sensor that can start to pull timing and get progressive in the timing pull the more times it detect knock.


no intercooler? why?!? you have unlimited cooling potential and you are not going to use it? that's just dumb. plus you are trying to stave off detention

awful idea, when did they spool up? use an internal WG and move on. you normally want power thats why one would use a turbo, so you want it spool up ASAP then bleed exhaust energy to control. unless you are trying to delay spool up to protect the stern drives
1. no EFI, not in the budget. A basic EFI system would start at 2000 per engine-. The new system will be blow thru. I already have the carbs and fuel pumps off my other turbo engines. M&W had a bolt-on blow thru system that added 90 hp to a bone stock 330 back in the 70's/80's with no changes to the engine. They even used the stock Q-jet carb.

2. no intercooler because of even more cost and complexity. I would need 2 intto 1 intercooler, mounts for it, water pickups, hoses. so by the time that is all done, Im looking at another 1000 per engine.

3. the reason GB didnt use waste gates back then was because of added complexity im guessing.
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Old 02-13-2019, 08:32 PM
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Originally Posted by phughes69
1. no EFI, not in the budget. A basic EFI system would start at 2000 per engine-. The new system will be blow thru. I already have the carbs and fuel pumps off my other turbo engines. M&W had a bolt-on blow thru system that added 90 hp to a bone stock 330 back in the 70's/80's with no changes to the engine. They even used the stock Q-jet carb.
carbs, meh... but ok.

Originally Posted by phughes69
2. no intercooler because of even more cost and complexity. I would need 2 intto 1 intercooler, mounts for it, water pickups, hoses. so by the time that is all done, Im looking at another 1000 per engine.
you are still going to have to plumb it up so that a wash. mounts are easy enough get a sheet of aluminum for home depot. and make your own. should be able to T off of the inlet coming from the stern drive.

ebay is your friend.
https://www.ebay.com/itm/Universal-w...frcectupt=true
https://www.ebay.com/itm/Aluminum-Y-...frcectupt=true

more like +250-300/per motor


use that link you can do a rough calc of what your turbo discharge temps will be. you want to pull that heat out of the intake charge. you will want to remove any increased change of pinging or detention, as stated above those motors have a weak bottom end. what going to be more expensive, doing it right or doing it twice and right?
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Old 02-14-2019, 01:20 PM
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to throw another idea in the ring, what about finding some LQ4 motors, super strong form the factory, tons of cheap twin kits. make the same power if not more AND then you have a ls twin turbo boat:P
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Old 02-14-2019, 02:19 PM
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Originally Posted by LTZCrew
to throw another idea in the ring, what about finding some LQ4 motors, super strong form the factory, tons of cheap twin kits. make the same power if not more AND then you have a ls twin turbo boat:P
That's what I'm doing with my boat, I'm going from a 5.7L to a 5.3L. the 5.3L has more HP & Tq than a 5.7 in both peak and area under the cruve. I picked up a running 5.3L motor, wiring harness, and ECU for $600. A 6.0L LQ4 in the same setup is about $700-800. Biggest cost is going to be the exhaust manifolds, not many option for an LS motor. There are some ford manifolds that can be used but you will needs to drill and tap 2 holes in the heads. you will also need to convert to closed loop cooling if you're not already as in my case (but it is a fresh water boat, so?). motor mount adapter or custom motor mounts are also needed as they are different. the stock pan can work but its a little light in oil capacity IMO, only 6qts, would be happier at 10-12qt. larger capacity oil to water cooler is on my list. the stock 350 bell housing will work 7 of the 8 bolts line up. fly wheel is the next issue to address, not finding any direct swap/bolt on option yet.

trying to keep my whole swap and conversion to EFI under $1,500. spent a lot of time researching this.
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Old 02-14-2019, 05:03 PM
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I don`t mean to discourage you but this is a stupid idea, hope that helps.
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Old 02-14-2019, 08:47 PM
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late 60s there was a company Daytona marine that put twin ray jay turbos on a 427 tall deck truck engine think it made 425hp intercooled at like 3800rpm blow through carb. Water jacketed turbo housings was very nice set up. And was fresh water cooled.
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Old 02-15-2019, 07:55 PM
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the early '80 s Gale Banks twin turbo kit for that era 330's was adveratised as a 425 hp output. I saw one engine spit the rod out of the bottom of the pan but otherwise they did as as expected. when comparing that setup in a 30 Scarab with the Gale Banks twin turbo kit against one with the factory Mercruiser HP 475 twin turbo the 475's seemed much stronger than 475, low 80's vs mid to high 70's same hull but the 475 setups had a higher X and speedy II drives vs the std 330 with TRS. The 25" merCleaver was probably limiting the TRS boat also. Good Luck
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Old 02-15-2019, 09:11 PM
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Budget builds usually cost 3X more than doing it right the first time, but I’m genuinely curious to see how this plays out and wish the op the best of luck.
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Old 02-20-2019, 03:28 PM
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Originally Posted by Baja Rooster
Budget builds usually cost 3X more than doing it right the first time, but I’m genuinely curious to see how this plays out and wish the op the best of luck.
Most accurate post on this thread!!!
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