383 dyno success!

[wca_tim]

Re: 383 dyno success!

you could always just install a bigger fuel check valve, tank pick-up and screen and potentially fuel line. I had to redo the fuel lines to ensure good fuel flow once I started spinning 4500-6000 rpms. first run at 5000 turned the plugs white - and I knew it was jetted fat. scared the crap out of me. I also installed a fuel pressure gauge, but as long as the fuel system is sized for the engine, it is just for info anyhow...

the stock fuel pump is just fine for a lot of power as long as you have big enough fuel lines. the one in the tank can be a problem if it is old and rubber, it can get sucked close if it doesn't have a spring inside of it...

also as an aside... a 24 laser is the smaller hub (even numbers), you want a 23 or a 25...

 

[JHuck]

Re: 383 dyno success!

Thanks for the heads up on the prop size Tim.

I have a decent sized hard plastic pick up tube and my hose is 3/8". Based on what n2o wrote, I'm hoping removal of the anti-siphon ball took care of the issue.

 

[n2ostroker]

Re: 383 dyno success!

Thanks for the heads up on the prop size Tim.

I have a decent sized hard plastic pick up tube and my hose is 3/8". Based on what n2o wrote, I'm hoping removal of the anti-siphon ball took care of the issue.

That check ball also keeps fuel from siphoning the tank should a line be cut or something happen to the fuel system. You should try to find a check valve to put in line directly after the tank or have some way to stop fuel flow.

That ball will definitely kill fuel flow though. In a carb system you can have enough pressure but not enough volume and not know till it's too late. I'm still playing with jetting/metering rods on mine. My tach died after hitting a big wave so I'm just running around this weekend til I can fix it

 

[wca_tim]

Re: 383 dyno success!

putting everything back together today... engine complete again, interior painted, etc, etc, etc... took an extra day to do a good job painting the (outer) transom assembly and outdrive. Logged in here to double check a couple of things before putting lower shift cable back together. Beautiful day to hang out in the back yard under the shade trees and relax while putting everyting back together...

Note I tried a bigger pump (electric) but it was too much pressure for the edelbrock carb I was running. The engine builder / shop was like: stock fuel pump is propbably plenty even if we put a blower and a lot bigger carb on that motor...

I did order a bigger checkvalve and replaced the tank pic-up and screen as well as linces to the filter water separator. I made sure that was the issue by running without a checkvalve and sure enough the fuel pressure was right back up there and no longer surging. I think I had enough restriction in the line that it was cavitating at the pump undfer high demand. damn good thing we didn't go with a blower or it would have been ugly.

I know a little off track for this forum, but what props have you tried again? and as an aside, for some reason in commenting on prop pitches, etc.. earlier in this thread, I got your set-up confused with someone else who was using a v6 gear ratio... sorry if I created any confusion. Your numbers actually seem about right with a little room for improvement as you get set up dialed in.

I'm not sure you're going to be happy with a laser nand would be surprised if you can't easily break it loose in the corners if not at will from start. with your power I can imagine that you'll find that well made 4-blades are the ticket. Although, this is based on my experience and with the higher gear ratio (more reduction) I've got more torque at the prop shaft. I can turn a 27" mirage to 5500(+) and the fastest prop so far is a hydromotive quad 4 (28 or 29" at 5200 rpms). I've got a spinnelli and a labbed mach 4 sterndriver in 27 and 28 pitch respectively to play with tomorrow and am going to start to let the rpms spool up as high as 5700 - 6000 or maybe a little higher if it keeps pulling... one of these days I'm gong to spend the half day to run on the dyno as it is set up in the boat to see where everything is at.

Sorry to ramble... go with larger fuel lies and tank pick-up, but put a check valve back in it as soon as reasonable - if you have an accident, the check valve keeps the fuel from being siphoned out of the tanki into the bilge... and could save your bacon.

Too bad you don't live closer, I've got several 3 and 4 blade props in the 21" - 26" range you could try before cuoghing up the dough to order a new one...

OK, found what I need, back to the task at hand. Keep it up on your toy - it'
s been interesting reading...

 

[JHuck]

Re: 383 dyno success!

Tim-I am running a stock 1.47 gear in my Alpha with a 21P Turbo 3 blade. I think it measures 14.25".

Do you remember the part # for the larger checkvalve you bought? I did a quick search the other day and didn't see anything.

Right now the Turbo prop is decent for 75% of our boating. It pops me up on slalom no problem but can still push the boat to a decent top speed. The other prop would be for giggles to allow me to see how much I can wring out of it at WOT (70 would be nice). If I thought I would be doing a decent amount of towing on any weekend then I would swap the speed prop for the 21P.

I am keeping my eye on Ebay right now because I bet there will be some holiday weekend boaters that will be looking for a different prop set up after the 4th. I also wish I lived closer to fellow speed enthusiasts to be able to play with different brands and pitches. Maybe one of the marinas at Dale Hollow will let me try one for a small fee.

 

[beech2000]

Re: 383 dyno success!

Great thread. Lots of reading that applies to my boat and thank you all.

Do all gas tanks have that check ball and spring mentioned earlier in this thread?

2years ago I replaced the 5 liter 2 bbl with the current 5.7 liter engines that pumps out lots of power and the engine used to cut out on me during early plane out.

I thought AFB bowls were running out so I replaced the original pump with a carter unit and problem went away. Could I have masked the problem with the big pump?

Thanks

Kevin

 

[n2ostroker]

Re: 383 dyno success!

Whenever I do a high performance build for a road vehicle, I install a wide-band O2 sensor and a meter, so I can see EXACTLY what my AFR is.

Because that isn't an option in a boat (unless you run 2010 style exhaust manifolds and o2 sensors) I often wondered if there was some alternative. I wonder if anyone makes a sensor that you could install into you're float bowl that will tell you if your fuel drops bellow a certain level.

Oh but you can add a wideband. They make a spacer. Might have to mod the exhaust some but if you have room it can be done. Here is one. There are others I've seen too.

http://cgi.ebay.com/ebaymotors/OXYGEN-SENSOR-FUEL-INJECTION-MERCRUISER-EXHAUST-O2-EFI_W0QQitemZ310137061646QQcmdZViewItemQQptZBoat_Parts_Accessories_Gear?hash=item48359c010e&_trksid=p4506.c0.m245&_trkparms=65%3A12|39%3A1|72%3A1171

 

[JHuck]

Re: 383 dyno success!

In my ongoing quest to ensure the engine isn't fuel starved at WOT, I went ahead and checked the fuel float level this weekend. It took 1/6 of a turn to bring the fuel level up to the bottom of the sight hole where it dribbled out when I barely rocked the boat and trailer. I've got a fuel pressure gauge, some 3/16 line and a 1/8 NPT to 3/16 hose barb that should arrive today from Summit. I plan to take it out this weekend to see if there is a drop at WOT. Even if there isn't a drop, it ease my mind being able to monitor the pressure is at all times.

 

[JHuck]

Re: 383 dyno success!

I installed the fuel pressure gauge this morning and am in the process of mounting it in my dash. At idle, it reads 4 to 4.5 lbs. This appears to be normal from what I've read. My understanding is that if I take it out tomorrow for a quick run and it drops below 2 lbs then I need to go with a higer flow Holley marine unit. Sound about right?

 

[JHuck]

Re: 383 dyno success!

that's GREAT!!! where's the icon of the screaming wife when you need it? or a smiley with bugs in the teeth?

get her hooked on driving... if you dare



ps. what prop were you running? sounds like your rpms and speed are just about right

I finally got a video of the boat at speed and thought I'd share it in this old post. After a year, the 383 and the Alpha have held up. I haven't made any more mods as I'm happy with the current set up. Besides, the Alpha would limit anything else.

http://www.youtube.com/watch?v=0apwLzde940

You'll notice in the video that the boat is level at slow speeds and while getting on plane. This is a testitment to the SmartTabs. I love them! Even though the boat has grunt, I can tell when they're not down when coming up on slalom. I'll have my wife come around and I'll put them in the down position to pop me right up. If you are on the fence with buying a set, don't wait any longer.

 

[wca_tim]

Re: 383 dyno success!

How cool is that! Boat looks and sounds great!


one thing, I like the smart tabs, but kept breaking them. I've since gone with a set of bennett helm adjustables and they rock!

Glad it worked out for you and that you enjoy it!

ps. on engine mods: I upgraded my 383 to cnc competition ported afr 195 heads, holley 750 dp with a proform body, a different drive (ss)... and picked up another 10 mph... as well as more power throughought the rpm range...

 

[QC]

Re: 383 dyno success!

one thing, I like the smart tabs, but kept breaking them. I've since gone with a set of bennett helm adjustables and they rock!

You guys with performance boats should pay attention to this. I like Smart Tabs but LOVE helm adjustable . . . If you ever said to yourself "I wonder if I am losing any speed with my smart tabs" you would know in a heartbeat if you had helm adjustable as it takes 1.7 seconds to pull them all the way up . . . OK, maybe 3 seconds from slightly down. Also, that flat attitude at lower speeds can be really wet if you are heading into the wind into some bigger swells or big chop. With helm adjustable you can make the bow ride higher and cut down the spray. Sorry for the hijack, but those who have not used helm adjustable just cannot imagine the flexibility.

I know this is a year old thread, but a god read. I am not with those that suggests propping to peak torque is a good thing, but it is not the drive I am concerned about. If someone came on here and told us he had a 6.2 (stroker) 320 (factory merc) and he was propped to run at 4400 RPM we would all be screaming "your going to ruin your engine". So why if your stroker runs max hp at 5500ish do we suggest 4400ish when the 6.2 example in question makes max power from 4800 - 5200 and we FREAK below that? A carb changes this? What else is different conceptually? Components? There is not one engine manufacturer that recommends peak torque RPM for WOT prop selection. Why would we want that in this case? We're all smarter than those idiot factories that make thousands of engines for marine applications a year? Any sarcasm is not intended it's just the way I think these things through

As far as the drive is concerned, either RPM is problematic, peak torque puts the most load on the gears, and peak horsepower puts in the most heat (power) . . . Choose your poison

 

[JHuck]

Re: 383 dyno success!

You guys with performance boats should pay attention to this. I like Smart Tabs but LOVE helm adjustable . . . If you ever said to yourself "I wonder if I am losing any speed with my smart tabs" you would know in a heartbeat if you had helm adjustable as it takes 1.7 seconds to pull them all the way up . . . OK, maybe 3 seconds from slightly down. Also, that flat attitude at lower speeds can be really wet if you are heading into the wind into some bigger swells or big chop. With helm adjustable you can make the bow ride higher and cut down the spray. Sorry for the hijack, but those who have not used helm adjustable just cannot imagine the flexibility.

I know this is a year old thread, but a god read. I am not with those that suggests propping to peak torque is a good thing, but it is not the drive I am concerned about. If someone came on here and told us he had a 6.2 (stroker) 320 (factory merc) and he was propped to run at 4400 RPM we would all be screaming "your going to ruin your engine". So why if your stroker runs max hp at 5500ish do we suggest 4400ish when the 6.2 example in question makes max power from 4800 - 5200 and we FREAK below that? A carb changes this? What else is different conceptually? Components? There is not one engine manufacturer that recommends peak torque RPM for WOT prop selection. Why would we want that in this case? We're all smarter than those idiot factories that make thousands of engines for marine applications a year? Any sarcasm is not intended it's just the way I think these things through

As far as the drive is concerned, either RPM is problematic, peak torque puts the most load on the gears, and peak horsepower puts in the most heat (power) . . . Choose your poison

I like both poisons! I typically don't drive the boat hard...often, but it's nice to know the power is there. The nice thing about the high RPMs, the damn thing sounds sweet at WOT.

 

[JHuck]

Re: 383 dyno success!

How cool is that! Boat looks and sounds great!


one thing, I like the smart tabs, but kept breaking them. I've since gone with a set of bennett helm adjustables and they rock!

Glad it worked out for you and that you enjoy it!

ps. on engine mods: I upgraded my 383 to cnc competition ported afr 195 heads, holley 750 dp with a proform body, a different drive (ss)... and picked up another 10 mph... as well as more power throughought the rpm range...

Very nice. Any idea on hp? Does that put you in the mid-80 mph range?


In a moment of weakness, I looked at roots blowers this spring but then I came back to reality.

 

[CharlieB]

Re: 383 dyno success!

In a moment of weakness, I looked at roots blowers this spring but then I came back to reality.

Reality is what you make it!

Ain't nothing wrong with using a Blower,

IF,

You do it right.

I've run this one 30 years, so far. but it is not on my boat.
Well, I guess this old browser is not going to let me attach a jpeg. Must be cause I'm still running Win98 on this box and can't install any updated browser. lol.
I have a straight 3 lobe Roots style Magnuson on my 79 Shovelhead, built during the Winter of 79, haven't grenaded it yet, and I turn it pretty hard sometimes well over 9 when I miss 3d gear.

If your thinking Blower, look into the Eaton twisted 4 lobe AND a serious raw water intercooler, guaranteed, it can be done safe, reliable, and surprisingly strong power addition, you WILL need to up-grade your drive even if you have added a 'drive cooler' sprayer.

 

[45Auto]

Re: 383 dyno success!

I am not with those that suggests propping to peak torque is a good thing, but it is not the drive I am concerned about.

I must have missed it in the thread somewhere. Someone is seriously proposing that doing something like propping a 5.7L engine for 3200 RPM (peak torque) at WOT is a good thing??? Why in the world would you even think about doing that?

 

[QC]

Re: 383 dyno success!

I must have missed it in the thread somewhere. Someone is seriously proposing that doing something like propping a 5.7L engine for 3200 RPM (peak torque) at WOT is a good thing??? Why in the world would you even think about doing that?

No, not exactly . . . but

We ended up with 466 ft/lbs at 4400 rpm and 433 hp at 5500 rpm. The lowest torque reading was 423 ft/lbs at 2900 rpm.

Now I need to calculate the new prop pitch. Should I base target RPMs on peak tq or peak hp? At peak hp, tq drops to 412 ft/lbs. Using a 21p 3 blade with 1.5 ratio right now (Alpha).

The OP's original question was what lead me to read the thread from that perspective . . .

You need to prop for 1000 to 1200 rpm over peak torque.

Too arbitrary, and depends on the engine.

Myself, I would prop it to keep it just under 5000 RPM (say 4800).

Decent rule of thumb, but not necessarily accurate for some builds, even factory ones like 350 MAGs or 6.2s . . .

I like wot rpms set where I would push for max speed - more like 5500 rpms, but then daily playing I dson't spin the engine over 5000.

Good, solid advice for this build . . . ultimately prop for peak hp then back off to save the drive etc.

I turn a SS Michigan something 14 1/4"x21 to 52-5300rpm. I also have a labbed 23 Mirage plus that I can only turn 43-4400rpm. Both run the same speed at WOT. The great thing about the Mirage is I can cruise at 38-3900rpm at a little over 50mph. Funny thing is both of these props run the same rpms with just me or myself and 3 others with a full tank. They might drop 1-200rpm when heavily loaded and I have a great hole shot with both. The mirage just won't turn anymore rpms.

Struck me as odd, and almost recommends the peak torque target thinking.

Running the drive propped for peak torque will put the drive in constant torque load and that Alpha will not be happy.

And this is why I commented on the drive . . . the fact is that no matter where you prop the combo, the drive is always under "constant" torque loads, just rarely peak torque if you prop for peak hp.

Despite a lot of good posts, it just seemed to perpetuate some misconceptions between the two measurements and the confusion about prop selection. If some of these posts were taken out of context they are potentially damaging, but not far off within the context of the thread. And once again I got the feeling this thread blurred the distinction between force and power, and although I personally like propping towards the low end of the peak horsepower range, it also seemed some were suggesting that for this build low RPM is OK. As your post points out (45 Auto) if you consider propping at peak torque, some ratings would be particularly stupid, unusable and could result quickly in engine damage.

I guess ultimately my point was that propping any engine for WOT at any RPM other than close to peak horsepower is not a very good idea. Although there are some exceptions, understanding those exceptions is complicated.

 

[Tail_Gunner]

Re: 383 dyno success!

I guess ultimately my point was that propping any engine for WOT at any RPM other than close to peak horsepower is not a very good idea. Although there are some exceptions, understanding those exceptions is complicated.
__________________

........Care to elaborate... QC have you been hanging around diesels to long...

 

[QC]

Re: 383 dyno success!

Not really, even diesels we prop for peak horsepower . . . That's what you pay for and what makes speed. I hesitate going there because it is always a disaster thread, but high peak torque rise is most appreciated in wheeled applications, not marine as many preach.

I guess I was thinking more of the guy who has a marginally powered boat and skis, so he under props which [may] put him way above peak horsepower [RPM] but just controls it with his right hand . . . Examples like that. I used to rent Houseboats that were propped way low [in the RPM range] too . . . I think they [over propped] as a cheap RPM limit [by going with too much pitch], and it was in the face of much of what we preach AND they were operated at WOT a LOT. I am guessing they didn't buy engines every week, so it must've worked for them. They were 2.5 120s (stringers) and were propped well below 4000. As low as 3400 some and I was always PO'd as the port and starboard would never match at WOT, so who knows . . .

Other examples are electric drive workboats where you might "prop" for a load at an economic RPM below peak hp, and yes, a diesel . . . So again, gets complicated as we begin to throw in variables not associated with our typical pleasure boater here.

 

[Tail_Gunner]

Re: 383 dyno success!

Dang ....I really enjoy it when you and 45 get going...Lots of good stuff in some of those conversation...