Brand New 5.7 Vortec - Only 3000 RPM on water?

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

imported_John_S,

Im going to look for the part number in a minute...

I found that same info when I looked for a 650CFM edelbrock online.

I had a different Carb on it after the motor was first installed on a monday, but after 2 days of testing props I realized the secondaries were not opening properyl... I suspected that was causing the lack of power issue so they swapped the carb out for the one I have currently.

However I did not see any improvement and now I think I have two issues now a non-marine carb and my original problem still...

Followup coming soon..

Thanks for your input!

Dan

 

[chiefalen]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Ok did you ever check if your tach was set to 8 cyl. Simple no money involved. Just look on the back.

You said it's brand new.

My friend had to adjust his valves set way to tight wouldn't let him go over 3000 rpm. Michagin motors. Rebuilt long block.

And thats after we went crazy trying to figure out why.

Plus i'm just assuming you ain't waterlogged. And have a clean bottom.

 

[MikDee]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

I have gained an inch on each arm and lost an inch on the waist plus a few pounds, so I guess that's good

I'm LMAO! on that line QC, I hear ya,,, the type of painting, & varnishing, you're doing would drive me wild, I've done it in the past, and avoid it at all costs now Good Luck with the project.

Dan, a 5.7 motor is 350 cubic inches, if you really have the high performance Vortec motor, I can understand your concern, but I doubt that the hp rating is that high? Yes it should rev up to about 4600 -4800 rpm, and do better then 26mph. I don't know the exact specs on your motor, but I'd think you need to run 92 + octane to begin with.
Changing out the antisiphon valve, & fuel pickup, and checking your fuel lines up to the engine, is always a good idea.
Yes, I believe the Edelbrock does have mechanical secondary's, with a weighted counterbalanced air valve on top that should open when engine vacuum calls for it (unless there's a linkage binding somewhere?). Either way, IMO, I find it hard to believe your boat could reach 40mph, or even close, with any Chevy 350 small block.

 

[QC]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

1. If the tact were not Brand New and shows the engine reving to 4800+ RPM under no load I would say that you may be correct here. I have no reason to believe that there is a Tact Issue.

1) THE TACH IS WRONG (see #3). Brand new makes me even more confident that it is wrong. See Chieflan's comment . . . Do not spend any money or time working on additional perceived problems until you verify that the tach, gear ratio, prop pitch and speed are dead nuts accurate, one or more of those numbers MUST be wrong. IMPOSSIBLE See #3. Doing anything before that is basing all of your choices on bad info. Sorry to be so emphatic, but this boat is going faster than it possibly can at 3000 RPM . . .

2. I have heard from multiple sources that a brand new 2008 5.7L Vortec Engine (330HP) (which is what I have) (This is the same engine SeaRay is putting in brand new 270's) will push the boat (a 7000lb Deep V-Hull w/ 100 gallons of fuel) 40+ MPH

2) There is no such thing as a 2008 5.7L 330 . . . None, nada, ain't one. SeaRay is putting 6.2 320 bhp MXs in brand new 270 Amberjacks, and 300 bhp 350 Mag MPIs in 260 Sundancers. The only Carb'ed engines built by Merc that were rated at 330 bhp at the Flywheel were 454s . . . You have a Carbed 350 cubic inch Vortec. Unless it is VERY built it makes less than 300 bhp. Horsepower is horsepower. You do NOT have anew, empty, perfectly test rigged 270 SeaRay that might do 46 with a 300 MPI. That will be the first and last day it will do 46. They are never as fast as the test boat. Never!!!!!!

3. I do not understand what you mean impossible... On my last test run with a 15.5d x 13p Prop I pulled 26.5 Knots (GPS) or 30.47 MPH while only turning 2900 RPM. So it makes since that another 1500 RPM would get me an additional 8-9 Knots or approx 10MPH.

3) Even more impossible than your last specs. Now. . . this assumes that you have your gear ratio, speed, RPM and prop pitch correct. Props ALWAYS "slip". Water is not a solid, so when you turn it around once it will travel forward 13 inches ONLY if it is turned trough a solid. Sine water is not a solid the propeller will only travel forward some distance less than 13 inches. This difference is called slip. I would be very surprised if your boat achieved 15% slip (lower is better). Right now your boat is achieving a negative 25% slip. Basically the numbers you have provided say that your boat is going 25% further than your propeller could travel through a solid (zero slip). If I crank all of your numbers into a prop calculator except RPM and assume a 15% slip (boat goes 15% less far than the propeller would travel through a solid) then I get 4280 RPM. If I use a more reasonable 18% slip for your type of boat, I get 4437 RPM. Which I actually believe . . .

 

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

chiefalen,

I will have to check the tach as you suggest...

It is from michigan motorz (See Link)

Engine Instrument Panel:
http://www.michiganmotorz.com/Marin...gine+Instrument+Panel/Engine+Instrument+Panel

I will follow up soon thanks.

Dan

 

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

MikDee & QC,

Im not an engine or boat expert in any way (as you can tell), but with my old (original enigne) 260HP 5.7L I could go 30 knots (based off GPS) when all planed out...

I can only hope that a 75HP increase would produce a few extra MPH????

I realize this is not true HP at the Prop, but 260hp vs 325hp is a fair comparison (apples to apples).

lastly I do not understand why there is doubt about the true HP of this motor...

Too MANY people sell this 325HP Carb version / 330HP Fuel Injected version motor for this to be BS.

I have even seen a 365HP 5.7L(350CuI)

Dan

 

[MikDee]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Ok did you ever check if your tach was set to 8 cyl. Simple no money involved. Just look on the back.

You said it's brand new.

My friend had to adjust his valves set way to tight wouldn't let him go over 3000 rpm. Michagin motors. Rebuilt long block.

And thats after we went crazy trying to figure out why.

Plus i'm just assuming you ain't waterlogged. And have a clean bottom.

Good catch, now I see why you mentioned the valves, & tach

 

[QC]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Im not an engine or boat expert in any way (as you can tell), but with my old (original enigne) 260HP 5.7L I could go 30 knots (based off GPS) when all planed out...

That is the most important and relevant piece of information that you have provided . . . It helps us gauge the performance now against a known #

I can only hope that a 75HP increase would produce a few extra MPH????

A 75 bhp increase will definitely push her faster.

I realize this is not true HP at the Prop, but 260hp vs 325hp is a fair comparison (apples to apples)

Only if it is truly making 325 bhp. This sounds like an automotive engine . . . at what RPM does it make 325?

lastly I do not understand why there is doubt about the true HP of this motor...

Because a properly marinized 5.7 Carbed engine usually doesn't . . .

I have even seen a 365HP 5.7L(350CuI)

And NASCAR 350 carbed engines make 800 . . .

Dan,

You have got to get the tach right or none of the troubleshooting you are doing is going to be based on valid info. This is the ENTIRE reason I have been so strong with my comments. With that said . . . I think the engine is probably not right. You should be able to exceed your old speed provided two things:

1) You actually do have more horsepower and

2) That everything else is setup to take advantage of that additional horsepower . . . mainly the prop . . .

Get us some engine specs. Where'd you buy it? Do they do dyno tests? Maybe it's in here somewhere, but did you buy it complete? With fuel system? Marinized properly? That's the stuff the rest of these guys are stronger on than me and I will not comment, buuuuuuuut. Ya gotta have good data or it is all worth nothing, nada, zippo . . .

 

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

QC,

You sound like you know what you are talking about, thats for sure!!


I will check on the tach setting tomorrow after I call MM to inquire about the default settings on the inst. panel.

Here is a link to the motor I purchased...

http://home.att.net/~daddyosmarine/product_1.html

Only difference is they swapped the carb after the first was not working properly.

I now have an edelbrock 1406 (which I now realize is NOT a marine carb)

Do you see any thing about this motor that seems "not as advertised" or "false" ... These guys have a good rep in south florida (I did my homework before selecting them)

Dan

 

[QC]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

I can't tell if it is a GM factory crate motor or not from the webpage. It shows a long block and a complete, and I can't tell which one they are advertising. Also, I am always leary of website addys that are from a generic ISP. Same as you get for a family account . . . Other than that, they look like they sell Marine stuff, but I would want to understand why I got an automotive carb then . . . Good luck getting her right. We will all help you do so.

 

[Don S]

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.

 

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Thanks chiefalen & QC.

I could not wait until tomorrow...

I had to grab a flashlight and check the back of the tach as suggested by chiefalen.

It was NOT set to V8!!! (good call chiefalen)

This is why I normally pay professionals to work on my boat in these manners.

Ok so I'm pass step one... Thanks QC for insisting that I start at step 1 (the tach) now I can go run and see what she does.

Also I replaced the check valve (which was partially clogged at this inline filter(screen), and will replace the inline water separator / filter before test.

Next stage is too open water test it and go from there...

Thanks again...

 

[chiefalen]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Have someone you can trust to re-adjust the valves?

 

[krisnowicki]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

to take advantage of the new hp you are going to need to reprop. But before you attempt get some good rpm/speeding readings. You need to find where your Wide open throttle is and then add or subtract pitch to get it between 42-4800. Every inch of pitch is 150-200 rpms.

 

[QC]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Considering the tach was set wrong and my calcs, I am reasonably confident it was at least 25% off. In one of the scenarios I did above with the 18% slip it is almost 33% off which requires that you need to multiply indicated RPM by 1.5 to reach actual which would say that your free revving deal that showed 4800 RPM actually exceeded 7000 . . . I have no idea what overspeed protection is built into that thing if any, but I am reasonably confident that it has been revved past 6000 RPM (25% indicated error). I have no idea when valves float on a Vortec, but I think those who have suggested that you take a look at your valve adjustment are correct for more reason that possibly tight ones . . . I could be all wet, so somebody that knows when these valves float, or somebody that knows what overspeed protection is in there, please chime in . . .

 

[DanielADeYoung]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

OK Guys,

I will start back a step or two...

1987 Searay Sundancer 268 (27') 7000lbs Deep V-hull

New Engine (5.7 Vortec 300+HP) + New Alpha I SternDrive (same as old one and it's a 1.5 ratio) + New Shifter + New 15d x 13.5p Prop (I do not know the old prop specs (only serial number xxxx) plus it was damaged on last use (old motor) to test now.

I replaced the fuel filter & anti siphon valve.

Last test was:

MAX RPM 3900/4000

MAX Speed 26.5/27 Knots (30/31MPH)

Questions:

What happens when I go up or down in diameter?

I understand how pitch affects RPM and hence speed, but I cannot find info on diameter.

Also how does 3 vs 4 blades effect top end speed?

When I ask people or use prop selectors utilities I get suggestions in the range of:

14-16 diameter (I currently have a 15d)
15-21 pitch (I currently have a 13.5p)

Since I can only get 3900/4100 RPM on a 13.5p so there is no way I can go up in pitch, and it seems like I may need to go down 1 or 1.5p

My real world situation seems "off" of all the recommendation I have been given for a prop.

Is it possible that I should use a 16d x 12p prop on this boat?

I look forward to any other suggestions

 

[MikDee]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

A 15" Diam. prop is about right, there's a good amount of blade area there for that pitch, more diam, or blade area will only slow you down,,, There is still something wrong if your last engine 260 merc did 30knots, set up this way, and this hi-perf engine can't surpass that, and it's not the prop.

 

[DanielADeYoung]

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)

 

[HT32BSX115]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

Howdy,

I don't remember if you mentioned that your prop is a stainless steel type but you may be getting some blade flex.

If you plug your numbers into a prop-slip calculator, 1.5 ratio, 12p 5000 rpm, you'll get a theoretical speed of 38mph and with 15% slip (common with single props and a planing sport type hull) you get about 32 mph......with a big heavy cruiser, you may experience higher slip.....a LOT higher with a large load......

I see you've verified your tach. (at least you have the switch on the right setting now.....kudos to whomever suggested that!!) It might be a good idea to verify it with another known tach. Even new tachs can be as much as 500 rpm off at the upper end of the range.

Another thing to check that I don't think was mentioned (maybe you have this covered): You said this is a "new" drive.....Is it really "new" or is it simply rebuilt.....nothing wrong with it but if it is rebuilt, or "remanned" did you absolutely verify the ratio? If it's "taller" than your original 1.47 drive you could be just a little "high geared" and enough to limit your top RPM.

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..... Mercruiser now claims 320 propshaft hp with a 6.2L EFI small block. That translates into about 350hp crankshaft hp. (my 454 is rated at 300 propshaft/330 crankshaft at 4600 rpm)

If you had a 260 propshaft hp engine/drive combo originally, and you're at about 300hp now, you only increased your propshaft hp about 40hp or so. (it may be more of an increase too.....In 1987 I cannot remember if Mercruiser rated their sterndrives at propshaft or crankshaft .......but, my OMC King Cobra 460 was rated at 340hp crankshaft in 1987........my Merc 454/Bravo III was rated at 300hp propshaft in 1997)

IMHO a 40hp propshaft increase at the top rpm probably wouldn't increase your top speed much on a big heavy boat.....few mph at best....


Regards,


Rick

 

[fishmen111]

Re: Brand New 5.7 Vortec - Only 3000 RPM on water?

QC, Don, and the others know ten times what I ever will, but an Alpha 1.47 in a 27' boat? Sounds too narrow a drive ratio to me and are having to prop down to compensate. Are you sure that is what you took out?