captain yarrr
have you tried anything lately,,,, what are you results as now

After more calculations and looking at the dyno sheet: my props are just fine for right now. What's holding me back from turning more RPM is my throttle bodies. I need to get some bigger ones and I can get some more RPM out of her.

have you looked at holley? Do you have some in mind that your thinking about

I haven't looked in to it at all. If anyone has any suggestions or experience, I'd love to hear about it. We are at least leaving 15 HP on the table with the stock one. Probably more.

I think your props really need a good lab job and you could pick up a couple of mph and some rpm with the power you have now. No doubt the throttle bodies will get more HP though. I'd send the props to BBlades this fall no matter what you do on throttle bodies.

BBlades told me to wait based on the dyno. Not looking at them right now but off the top of my head it makes 400 at 5200 and 400 at 5500. He says that's why it's not pushing more RPM, because it's not pushing more horsepower across the range.

We agreed: let's do throttle bodies, see how she does and probably at that point start making some changes. Maybe labbing some 25P props was his thoughts.

So Bob, what throttle bodies we putting on this winter? :)

Captain, Curious to know if you are using the stock 4 quart oil pans.

Yes that's all stock and my cooling seems to be working well.

Hey Yarrr, I too have a 32 Sunny MCOB with 6.2s and will be doing some builds soon. Just wondering if you found the right prop setup, did you change anything as far as shorty lowers, extension boxes, etc. and what has been your best top speed? I am itching to start these builds and going open checkbook. Any info would be greatly appreciated. Thanks

Also, why the small/stock oil pan and who programmed your ECM? Have you had any issues since the builds?

What is prompting the builds? Did you lose one or both? I'm holding off on props as I mentioned earlier. Bob put a 4 BBL carb he had laying around and made another 15 HP, so we know the throttle body is choking the engine some. BBlades thought I should wait until I do that, then probably jump up to a 25p and lab that. So far I've got a max of 72. One of the engines is giving me an alarm at WOT so I've not been doing any hard running besides long cruises until I scan it. Which she's done great on, I've kept the stock oil pan because it seems to be working great. Ran 3500-4k RPM from Clear Lake TX to Galveston, TX and my oil temps were perfect. If I wanted to lab what I have, they think there is a few MPH there. But, really...I'm just loving the acceleration and having a great running boat again so it's not high on my list right now. I forget who programmed it, I could dig it up when you're getting closer.

See post #22. Bob added oil coolers. A must IMO if doing this build and keeping the stock pans.

Just want to run faster. I'm a little bored with running 65-70mph. The plan was to sell off stock engines and start from scratch with Dart blocks stroked to 406. Simple additions like dart aluminum heads, a mild custom cam, aftermarket intake, headers, pump gas compression and I'm thinking around 450hp each motor. I would like to keep the fuel injection so I'd have to research a tuner. Would like the computer tuned while under a load versus sending away computer for tune. Would like to see 80mph plus on a light load

If I were in your position I'd sell your stock engines and buy one of these bad ass big block setups I see for sale. You'd spend similar money. If not that, I'd sell them and do an LSx build.

I love my engines but I only did the build because I had to rebuild them either way and this build wasn't a ton more.

I can't do big blocks because they are a different size and won't line up with the existing transom setup. I am going to try a reputable engine builder that can do the builds and tune. This way it's turn key ready with what I hope are no issues.

Where are you at? If you do dry headers you will hit 450 easily with my build. We held back a lot on the cam and if you do throttle bodies you might even do better.

I would really read over the Skater LSx build if I were you. That thing is nuts.

Hey guys, I just dyno'd a small block for a 68 Camaro. It was a 427, dart block with dart 200 cc heads, 10:1 compression and a pretty big hydraulic roller cam, single 4 bbl carb.. It made over 600 HP at 6200 RPM. I was really impressed with the numbers. You could build a similar marine version that would easily make well over 500 HP in full trim.

Dart/AFR406
 

The attached build sheet is for a marine Dart SHP 406 w/ AFR 195 cc heads with a mild hydraulic roller. This went into a Magnum Starfire ~ 5 seasons ago. A very tractable, durable piece.

Bob

Can you send me the link for that skater build? I never heard of a LS1 in marine application. At this point, I'm doing research and trying to educate myself. What I'm looking for is an 80mph boat on a light load. If you use the 11hp equals 1 mph gauge, I figure I can attain that goal with a 450hp setup. I'm a cruiser type of guy who likes to cruise at around 40-50mph, but every once in a while I like to open it up. Reliability is the most important factor in any build because there is really no point of doing anything if you are going to be broke down often or doing frequent tear downs. Plus, if I can get by with my bravo 1 setup, that's money in my pocket as well.

What was the cost of something like that, injected or Carbureated and if injected, what kind of delivery system? Whichever route I go, Id want the combo tuned while in the boat

Bob,

What are the cam specs for this motor? They can be approximate as I understand the sensitivities towards industry secrets.

Yeah I'll do some hunting around for the link. Well, if you want a powerful small block Sunsation, I'd give bobl a call. I'd venture to say he's the expert on the topic. He got to become quite familiar with my Dominator at his shop. He can definitely hit your goals for you if you take it to him. This isn't his first 6.2L build either.

The big lingering question I haven't got a straight answer on is the X-dimension, if it is the same as the big block boats? Bob and I suspect my drives are pretty deep, likely scrubbing off speed. My boat hooks a little TOO well coming off idle. My boat makes more power, weighs less and isn't out-running the MPH I'm reading about on here with 454s. When she's maxed out, she's flying incredibly flat...too flat.

Have you contacted Sunsation direct about the X dimension? I called a couple of weeks ago to inquire about performance mods to my specific boat. Accordingly to Joe, he said the hull is pretty much dialed in to it's max capability so bottom blue printing or x dimension changes won't add speed. I believe he said the x dimension is set a little higher than the big block versions. I tend to agree because with my boat while accelerating from idle in rougher chop or trimming before boat has a chance to level out or ride at a certain speed, my boat suffers prop blow out. Joe told me that if you want to go faster, it's going to require increased HP and propping.

I did call but I didn't get a real clear answer. I asked one of my friends with big blocks to measure so I'll have a solid answer soon.

Almost any fast boat will blow the props if you trim too soon. What makes us believe it's deep is that with three blade props it won't blow out under most circumstances. It hooks a little too well.

what is the prop shaft height

Just wondering how your builds are performing and if you tried anything new. I remember you were talking about changing props. I have the same boat as you and if finances go well, I plan on doing some small block builds.

Reds, still running about the same. I bought some labbed 23s that I haven't had a chance to run yet. Been dealing with learning this lesson: If you do a 383 build, take the time to replace all your sensors. Been replacing the junk original water pressure, temp etc.

My PM box is empty now.

Thinking about giving it a try. Anyone have any knowledge of how the TPS and IAC work with a Mercruiser ECM? Is a TPS a TPS or are there differences that will cause me issues?

Evan, I just did an engine for Simon (Simon Sez 38 Fountain). It's a 350 that we did a similar setup to yours. This was my last build before closing the shop. We went with a Holley throttle body and it came with TPS and IAC. You have to re-pin the Holley IAC to work with the MEFI, but it worked really well. Made 421 HP with a set of marine headers.

Oops, forgot you have the ECM 555. You'd have to adapt the IAC to work with the new throttle body. Don't remember how we mounted it, but it shouldn't be a big deal. TPS should be the same.

Hey Bob,,, not sure if you remember tuning my engines, they made 400hp/425tq,,,, similar builds to Captain YARRR,,,, do you think we would have to retune the ecm to replace stock throttle body with the Holley throttle body

Probably not. I generally tune them a little on the rich side so a small increase in airflow most likely won't cause it to be too lean.
Obviously checking the A/F ratio is the only way to be sure. I tested a 1100 cfm throttle body on CaptYarr's engine. It didn't affect the tune much but definitely made more power. Seems like it was 10-15 hp increase.

Bob

Thanks Bob ,,, didn't know you retired ,,, hate not having a go to guy that doesn't mind working with SBC. Sure hope we can message you sometimes with questions

I built a shop at my house and kept my dyno. I will still be doing some projects...just only things I want to work on.

Bob

I would think the drought hurt you as it was bad here to. Now we are dealing with lakes still closed because of flooding. It has hurt me as well.

You are absolutely correct. It's been a downhill battle since the financial crunch, then historic drought. We had an opportunity to sell our building at a good price so all worked out well. I opened that business after I retired from a real "paying" job in 2000. Now I'm just going to play and work on a few performance jobs of my choosing.

Bob

Will add about MPI / EFI sensors as a lot of problems can be self inflicted - corrosion, poor connections especially at the battery and or starter, improper size wiring and cables, also poor grounds especially back side of engine, also weak batteries, low voltage and or bad cells plus that causes a lot of stress on the alternator along with the starter. Dampness in the engine compartment, Vibration and heat / overheat is a big killer.

Killers also for sensors can be RFI related and for the water pressure sensors, the power steering cooler is not grounded properly ( heavy black epoxy paint ) . FYI

Bob and Capt Yarr, did the exhaust matter much in this build? I understand the internal shape of the glm exh manifolds directs the gases, no problem there. But I wonder how much the ss risers matter? Are they superior for flow or against reversion due to some design element?

On edit, nevermind. I went poking around at the beginning of the thread and found a pic. I didn't know which risers you meant ti I looked at the pic.

I'd be interested to know where the cam is clocked though. Are you able to share the intake centerline that was used?

Well...
Its been 3 years since this great thread was alive!
What have we learned about the 6.2 MPIs that can help with a new 383 build now?