Brand New 5.7 Vortec - Only 3000 RPM on water?

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

MikDee,

I was guessing that since I the prop recomendations are all way off.

There is no way I can run a higher pitch prop with this current power.

I asked someone local about a 12pitch prop and he called it a pontoon boat prop???

I still need to find 400-600 RPM and because hopefully 4-7 more knots (top end)


Dan i would suggest you find a 14 dia prop maybe a 13p and go from there. You leg calls for a 14" dia and when you mate the prop to the drive that chould create a disturbance of water right in front of the blade area effectively messing things up.

Take you current prop and place it on the drive, where the two meet could you take a pic and post it. The prop barrel should line up to the drive bullet or what its called very evenly...if not you have a distubance in the water flow going on before the prop even gets a chance to pick it up and work....which is a bit confusing that would only create more slip and higher rpm...12p prop is very small for a 5.7 even on a 7000 lb boat...I assume your hull is clean..no old growth under there..
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

If you still have the marine carb, put it back on. Here is a list of causes of low WOT rpm. You know most are fine, but what about items 3 (Do the test) or items 11, 14 and 15.



Engine Won't Reach Operating RPM. Check


[1] Fuel condition. Type and Octane possibly old fuel
[2] Propeller pitch or diameter, damaged blades
[3] Restricted fuel pickup tube or anti siphon valve Fuel System Test
[4] Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
[5] Marine growth on hull and outdrive
[6] Wrong gear ratio in outdrive
[7] Restricted carburetor air intake (clogged flame arrestor)
[8] Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
[9] Poor cylinder compression Compression Test
[10] Carburetor defective, or wrong type.
[11] Fuel pump pressure and vacuum
[12] Boat overloaded, improperly loaded, or improperly trimmed.
[13] Engine Overheating
[14] Engine timing and ignition system operation
[15] Remote control cables and linkage for proper travel to open throttle plates fully.



Pay close attetion to that post....I would be very skektical if that carb is jetted correctly, there is usally a kit that comes with most aftermarket marine carbs...Bondo??

http://www.edelbrock.com/automotive_new/mc/carbs_acc/performer.shtml

600 cfm, Electric Choke
CALIBRATED FOR PERFORMANCE
Designed and calibrated for optimum marine performance in small-block V8 engines with a variety of manifolds that include Edelbrock Performer, Performer RPM, RPM Air-Gap, Torker II and other brands of similar design. Also ideal for Chevy 4.3L V6 engines with a Performer manifold (see Manifolds) and Calibration Kit #1485. Comes with: Metering Jets ? Primary .098, Secondary .101; Metering Rods ? .068 x .047; Step-Up Spring ? orange (5" Hg).

http://www.edelbrock.com/automotive_new/mc/carbs_acc/access_thun_perf.shtml

Tuning a motor out of the box takes both time and experience.. as you have already seen with the tach.. For one thing if that if that carb you have is auto it has a vacum system that is not being utilized by the motor a marine carb has no vacum system..Good luck.
 
Joined
Sep 7, 2008
Messages
14
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Rick,

Thanks...

Question what is a big heavy boat???

27 foot is not too big is it?

I?m guessing that it is 7500-8000 lbs Max (with fuel and crew of two or three)...

Is this too heavy?

I know there is a hull type issue to consider, but using the speed calc tool from that same site you provided shows better results then I get (even for my hull type)

I?m stuck at "just cannot believe that this new engine is performing better"...

Some people are implying that this is what I should expect and some believe like me there could be an issue to deal with.

I wish I just test drove it after the new engine was put in and everything was just awesome? now it money + time + more time & money!

Dan
 
Joined
Sep 7, 2008
Messages
14
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

fishman111,

99.9% sure it was 1.5 ratio (1.47) that came out.

That was however the original sterndrive for the 260 hp motor.

Should this new motor (300+ hp to be on the low side) use a different ratio for some reason IYO?

Dan

Dan
 
Joined
Sep 7, 2008
Messages
14
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Tail Gunner,

you suggest a 14diam prop vs the 15diam prop.

What can I expect to change if the pitch stays 13.5?


This was one of my questions...

FYI the bottom is good I would say 8 or 9 out of 10.

There is no growth, but the bottom anti foul paint is spotty (NOT really rough).

Dan
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Tail Gunner,

you suggest a 14diam prop vs the 15diam prop.

What can I expect to change if the pitch stays 13.5?


This was one of my questions...

FYI the bottom is good I would say 8 or 9 out of 10.

There is no growth, but the bottom anti foul paint is spotty (NOT really rough).

Dan

Actually your leg calls for a 15 dia prop, disregard unless there is a mismatch between the prop and the leg...Id look closely at your carb first off it's not a marine carb and that can cause you big ins problems if a ccident happens and you have a lot of money going on there what's 300 dollars..

http://www.amazon.com/Edelbrock-1409-Performer-Secondary-Carburetor/dp/B00062YA80

I find a hard time believeing you need anything more that that.
 

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

MAX RPM 3900/4000

MAX Speed 26.5/27 Knots (30/31MPH)
OK, I think the tach is still a little off. I would ask someone with a shop tach to ride with you to verify . . . I am getting 9% slip with your numbers which is too good, for definitely a heavy boat. For what it is worth, I am running 320 bhp in a 4000 lb boat, so yes 7000 lbs and 260 bhp (where I think you really are at the propshaft max) is heavy, not for a cruiser, but still heavy. . . . If I use 18% slip I get almost 4300 RPM which I think is more reasonable.

http://www.rbbi.com/folders/prop/propcalc.htm

I am really skeptical of their (Daddy-o's) claimed HP rating. and of course HP doesn't mean anything anyway.......it's torque that doing the work.....

I agree that their hp claims are high, but I have to respectfully and totally disagree with your torque comment. This is a personal crusade I am on to rid the world of this misconception. If torque was all that mattered then you shoud be able to run your boat simply with your right arm. The biggest among us can torque head bolts to 400 lb/ft. so if "torque is all that matters" . . . ;) Horsepower is defined as work done over time. Torque is simply twisting effort and alone it is good for very little other than torquing head bolts . . . However, in road vehicles, higher peak torque values will result in better acceleration and allow for better lugability, which will translate to higher road speeds under a load and/or climbing a hill. It doesn't translate so easily to marine and therein lies the confusion . . .
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

but I have to respectfully and totally disagree with your torque comment. This is a personal crusade I am on to rid the world of this misconception. If torque was all that mattered then you shoud be able to run your boat simply with your right arm.
Thanks for being respectiful!:D we should all do that of course....


I'll rephrase it....and of course you're right, torque is not explicitly "all that matters" .... but torque IS the important "thing" at what ever RPM you're considering. HP is just a number calculated from the measured torque at that RPM. so it IS really the torque that's doing the work......

(this is a really meaningless argument).........

The main point I wanted to make is, that the drive ratio and prop pitch should be selected so as to take maximum advantage the new engine max rpm torque (HP)

The
current drive ratio and prop pitch may not be optimum for this new engine.
 

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

(this is a really meaningless argument).........
But I think it is important only in that without RPM mixed in nothing matters, no work . . . Many would dispute the following statement:

200 lb/ft. torque at 5000 RPM is better for a boat than 400 lb/ft. at 2000 RPM

But it is in fact true if you want to make stuff go . . . which requires work.

Sorry to continue, but like I said, I am on a crusade . . . :rolleyes: Now add in thrust to this discussion and I will delightfully and respectfully defer to you as I haven't got a clue . . . ;)
 

gussie

Cadet
Joined
Aug 26, 2008
Messages
19
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

I am probably not alone in saying, " this is a very interesting thread, and I can't wait to see the end result or answer.

There are some very bright and experienced people on this great forum, and I should be very reluctant to try to add anything to the discussion.

I can't help but think two things:
1) This is a large boat to be pushed fast by the Chevy small block standard V8 engine
2) This engine cannot be developing the HP that the OP was anticipating. Compression? Fuel? Carb? Ignition? Cam?

Where am I going wrong?
 

scr350

Seaman Apprentice
Joined
Oct 2, 2008
Messages
30
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

i have a 27 foot maxum cruiser that has a 350 vortec that is 330hp from marine power. i have a 16x13 prop. its a alpa 1gen 2. it runs to 4800 rpms. speed with gps is 42mph. i kinda had the same thing happen to me when i replaced the plugs last year. i had 2 spark plug wires crossed didnt effect it out of the water but in the water it would only muster about 3000rpms. i dont know if that is your problem but it was sure mine. i use my boat for skiing,tubing and all other water sports.
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

i have a 27 foot maxum cruiser that has a 350 vortec that is 330hp from marine power. i have a 16x13 prop. its a alpa 1gen 2. it runs to 4800 rpms. speed with gps is 42mph. i kinda had the same thing happen to me when i replaced the plugs last year. i had 2 spark plug wires crossed didnt effect it out of the water but in the water it would only muster about 3000rpms. i dont know if that is your problem but it was sure mine. i use my boat for skiing,tubing and all other water sports.

For a Big boat, that's haulin! ;) and crossed plug wires, Yes, this can happen all too easily, and sometimes it's hardly noticable, except for a sudden power loss.
 

dolphin1

Cadet
Joined
Jul 19, 2007
Messages
20
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

just a little food for thought, I have a 2655 ceira with a 5.7 2bl carb (7200lb)loaded and I run a 16x16 prop. 3250 rpms at 26mph (gps) it will turn 4700 rpms wot. Didn't have my gps with me when i ran wot so I don't know top end but I will next weekend.
 

krisnowicki

Lieutenant Junior Grade
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Jul 11, 2007
Messages
1,172
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

If were your 350 2bbl i would be thirsty pushing that big boat. I would want a 4bbl. :)
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

i am really following this also, andwhat you mean by plug wires cross
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

i am really following this also, andwhat you mean by plug wires cross

Plug wires on the wrong plug, sometimes 2 get mixed up, firing order small block Chevy 1-8-4-3-6-5-7-2 clockwise on the top of your distributor. Make sure each wire goes to the right plug. If you're facing the front of the engine, (the belts, & pulleys), on your right it's cylinders 1-3-5-7, and on your left it's 2-4-6-8, trace them out.
 

TJEli

Cadet
Joined
Jul 21, 2008
Messages
28
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

I just read the entire thread and I think he is getting close to where this engine is going to perform. I know its not the news that the OP wants but that 325 hp rating is HIGH for that motor and compression ration and its also rated at 5K RPM. I would say you are running slightly more hp than your origional motor but hopefully you have more reliability now.

Verify the tach and prop her for slightly more RPM and have fun. (if everything else checks out)

-Eli
 
Joined
Sep 7, 2008
Messages
14
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Ok another short break and now more info.

I finally was able to line up a qualify mechanic to do a lake test (on water).
Zero wind? it was like ice on this small lake.
Barley enough room to make plan, to really get going we had to do a power turn and make plane on the back leg. No Problems as 80% of the back leg of the loop was on a plane, so I know the top end got tested.
Prop: 15.5d x 13p
Max RPM (no trim tabs or extra tweaking): 4200RPM
+ The Tach is accurate
+ The timing was about 5 degrees advanced
+ The throttle at the dash is restricted to 95% of the throw (need to remove it make a small notch and re-mount. no biggie.) This means the carb will open a frication more (100 RPM maybe...)

That is it? no other issues with the engine.
The mechanic (who drive lots of different boats) seem to think it ran very strong and this is what I should be expecting (as some of you have pointed out?) He also made a comment about the how 40 HP increase on this type of boat will be hard to notice.

I was only hoping to get to one of two places?
Find what?s wrong or go enjoy the boat know that I?m not f***ing it up.

I?m still stumped with the prop issue and why I have to run a 13p prop to be able to get into the WOT range.
I did not have my GPS with me this time, but since the Tach is right I can use the last test specs
Last test was:
MAX RPM 3900/4000
MAX Speed 26.5/27 Knots (30/31MPH) (GPS)

Question: Using the Prop Slip Calculator I see that I have like 9% - 12% slippage? does that sound right?

Dan
 

Don S

Honorary Moderator Emeritus
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Messages
62,321
Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Max RPM (no trim tabs or extra tweaking): 4200RPM

Use some trim! If you have the drive all the way down, you are plowing.
 
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