Brand New 5.7 Vortec - Only 3000 RPM on water?

[DanielADeYoung]

I just had a new 5.7 Vortec engine and a 100% new Alpha 1 Outdrive (1.47 ratio) installed into my 1987 Searay Sundancer 268 (27? cabin cruiser) (deep v-hull)

This was a $9,000 Repowering (now Im broke)

The engine revs to 4800 RPM (WOT) when it is out of the water.

On the water it only revs to 3000 RPM (26knts)... the problem!!!

I have replaced the shifter as well trying to solve this, but it is the same with the new shifter.

The engine shop has no answers to why this is the case.

The current prop is 15.5d x 13p (13p is very low and should be able to reach the 4400-4800 WOT, but it does not)

I do have one specific question about manual secondary?s vs. vacuum secondary?s on the carb.

I have manual?

Should the secondary?s open fully with the engine off and throttle pushed 100% forward? The primaries do...

I have heard yes and I have heard that the secondary?s open at like 3200 RPM

Thanks in advance? I want to enjoy my boat not put more $$$ into it!

Dan

 

[krisnowicki]

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

what kind of carb?

 

[Uraijit]

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

Did you do the repower yourself? If not, take it to whoever did it.

How's the timing? Was the carb properly set up? Are you getting enough fuel to the carb? Is it good fuel? Did you do a compression test? Are you certain they put a 1.47 ratio drive on it?

If you keep "frewheeling" the engine, it won't last very long. Revving the engine up without a load is a good way to tear things up fast... The fact that the engine will spin up without a load doesn't tell you ANYTHING about its condition.

 

[Maclin]

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

If you truly have a mechanical secondary carb on there, which I doubt, then the secondary throttle plates will begin opening at 1/3 to 1/2 throttle and be fully open at full throttle no matter if the engine is running or not. That is the exact nature of mechanical secondaries.

If you have a Vacuum secondary carb then it depends on the type of carb as to whether or not the secondary throttle plates will be moved if the engine is off.

A Holley vac secondary does not move the secondary throttle plates with the throttle linkage. The secondary plates will only open if the draw thru the primary venturis overcomes the spring in the vacuum diaphragm that is linked to the secondary plates opening lever. The opening rate is adjusted by changing out the spring in the vac diaphragm chamber.

A Rochester Quadrajet and Edlbrock or Carter carb will move the secondary plates with the linkage but that does not activate the secondaries as there is an air valve plate at the top of the carb that stays closed until the engine demands more flow, hence vacuum controlled secondaries.

A Rocheter QJ is adjustable regarding the secondary opening rate. Several systems work together, each has to function correctly, the main control is sprting tension, the spring can be adjusted. Do a search on Rochester quadrajet or even vacuum secondaries and you will find a lot of posts on the QJ and other carbs.

 

[chiefalen]

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

The valve springs too tight? Re adjust. New motor i wouldn't be surprised.

 

[MikDee]

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

If you have an orig, equip. Quadrajet carburetor, the bottom secondarys will open mechanically with the linkage, BUT, the secondary air valve on top will not open until the engine calls for vacuum, (when you open the throttle, it will slowly react) these upper butterflys are the most important, because the secondary metering rods are attached to them, and allow fuel flow into the secondarys, only when they are open. I suggest when in the water, and the engine is warmed up, you temporarily remove the flame arrestor, and look to see if they're opening fully, when you open the throttle fully under power.
Then get back to us with the results, so we can help you if needed.
(and please no free revving any motor in neutral, especially a new one)

 

[Maclin]

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

I like chief's valve lash adjustment suggestion also. Very common on new 350's to have them too tight.

 

[John_S]

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

Agree, that whoever did the repower needs to resolve. Once you dig in, it is all your problem.

Thats sounds like a heavy boat. What was it powered with before? and what was its performance? I'm not a big boat owner, but suspect you are still plowing water, and haven't come on plane at 3K.

I suspect, as others mentioned, you are probably looking at the air valve plate on the secondaries. Along with carb, we need to know what ignition system you are using. What is the advance at 3K rpms?

I am at a loss on why the hyd lifters would need to be re-adjusted on a new motor. If that is suspect, just about everything in the new motor would be as well.

 

[MikDee]

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

Agree, that whoever did the repower needs to resolve. Once you dig in, it is all your problem.

Thats sounds like a heavy boat. What was it powered with before? and what was its performance? I'm not a big boat owner, but suspect you are still plowing water, and haven't come on plane at 3K.

I suspect, as others mentioned, you are probably looking at the air valve plate on the secondaries. Along with carb, we need to know what ignition system you are using. What is the advance at 3K rpms?

I am at a loss on why the hyd lifters would need to be re-adjusted on a new motor. If that is suspect, just about everything in the new motor would be as well.

I agree with John, on a couple of points,,, valve adjustment on a new factory stock motor should be fine, and all the carburetor settings should be fine as well, they shouldn't need to be messed with at this time, just make sure the upper secondary butterflys are opening fully first, as I mentioned. The initial timing, and timing advance should be preset right also, but this could be off some, it might be slightly retarded? This can be checked, and adjusted if need be, but not until you check the carb. operation first.

I'm betting this is a heavy boat for a 5.7Vortec, some previous history of what engine, & what top speed was previously, would help.

I had an old 24' SeaRay cuddy cabin, with a 350/260 Merc that would only do 40mph fully trimmed out, so I'm not sure what to expect with a heavier 27' SeaRay cabin cruiser, maybe 35mph with full trim?

 

[QC]

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

26 knots guys!!!!! That's 30 MPH and I guarantee she is absolutely 100% on plane . . . An Alpha (harder to get out of the hole than a duo-prop or B3) that reaches that speed is not too far off. The fact that it gets up and actually goes says it is making some significant power. Like JohnS asked what was the performance like before? Check the tach too, if it revs to 4800 with no rev limiter that is waaaaaaay more than 4800 . . . . . .

Edit: This is negative 20% slip. Ain't no flippin' way . . .

Edit 2: The tach is definitely off . . . 18% slip puts her at 4400 RPM, that's a 30% tach error which puts the free revving party at 6240 and if there is a valve problem . . . well . . . uh . . . another

 

[John_S]

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

0r 25% slip if his tach is off, and engine is reaching 4800 range.

Speed and rpms are suspect.

PS: Good catch. My mph mind just skipped over those nautical terms.

 

[justarobb]

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

different boat same problem, check the plugs and wires.

 

[MikDee]

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

26 knots guys!!!!! That's 30 MPH and I guarantee she is absolutely 100% on plane . . . An Alpha (harder to get out of the hole than a duo-prop or B3) that reaches that speed is not too far off. The fact that it gets up and actually goes says it is making some significant power. Like JohnS asked what was the performance like before? Check the tach too, if it revs to 4800 with no rev limiter that is waaaaaaay more than 4800 . . . . . .

Edit: This is negative 20% slip. Ain't no flippin' way . . .

Edit 2: The tach is definitely off . . . 18% slip puts her at 4400 RPM, that's a 30% tach error which puts the free revving party at 6240 and if there is a valve problem . . . well . . . uh . . . another

QC, 4800rpm he was free revving the motor, that's not under load?

But, If his tach is off?,,,

By my Formula: If he's actually turning 4600rpm, divided by 1.5 gears = 3066rpm X 12" pitch (13 -1) = 36.79mph - minus 20% slip = 29.44 mph = ? knots

 

[QC]

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

Mik,

I know the 4800 was with no load, but I think it was over 6000 . . . 3000 RPM is 18% negative slip . . . AKA impossible . . .

Your calc works out to 26 knots (25.8 something . . .). Why do you subtract the inch?

 

[MikDee]

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

Mik,

I know the 4800 was with no load, but I think it was over 6000 . . . 3000 RPM is 18% negative slip . . . AKA impossible . . .

Your calc works out to 26 knots (25.8 something . . .). Why do you subtract the inch?

26 knots Okay,

It's a Formula I got out of "The Boaters Handbook" a small handy guide I borrowed out of the local library back in the 70's. I've been using it for years in my head, it is very simple to remember, & surprisingly quite accurate, works for inboard, outboard, or I/O, as long as you have the right gear ratio and your tach is right

RPM's - divided by gear ratio X pitch -1 = Speed - slip usually 15-20%

I used it for the prop on your mahogany speedboat replica, awhile back,,, forgot what it was though? By the way how's that doing?

Example: My 24' SeaRay, 4600rpm div. by 1.50 = 3066 X 16" (17 -1) = 49.05 mph - 20% = approx. 39.22mph, back then there was no GPS, my speedo said 40mph, and fully trimmed out, with muffled thru-hulls, that big old husky boat was boogeying! That's close enough for me

 

[QC]

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

The one inch thing still bugs as you could simply assume more slip. Handy formulas are cool though. I use this one online: prop calculator

My project timing has slipped some as I was trying to get done before the season and now I am thinking before next season . . . She's still upside down at this point. No real problems although I am learning some paint lessons the hard way. Sanded a good chunk of yesterday . . . 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

 

[DanielADeYoung]

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

Hey all...

Lots of great feedback THANK YOU.

I'm going to follow this through to the final solution, and post it here.

I just wanted to let everyone know what I have learned (from Searay dealer and other sources) and what I'm currently trying as trouble shooting.

This 1987 Searay Sundancer 268 with a 325/330 HP motor (single) totally trimmed out and the with the correct prop should...

Top out (4400 RPM) at about 40 Knots (46MPH)

Cruise at (3100 RPM) at about 30 Knots (34MPH)

1Knot = 1.15MPH when


Since the cheapest and most likely issue is with the fuel supply I have removed the check valve (anti-syphion) and will be replacing it along with the fuel sender (part that goes down into the fuel tank)

This will cost me about $40 bucks and 30 minutes to replace.

I will test the boat "on water" Sat (13th) and report back then with any changes in performance.

Next thing will be to have the electronic fuel pump and carburator looked at ( It is a 650CFM edelbrock w/ vacuum secondaries )

Thanks again guys!!!

Dan

 

[QC]

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

Dan!!! YOUR TACH IS WRONG!!!! Don't do any testing until you get the tach right, you MUST have the tach dead nuts and the speed numbers need to be GPS verified in no current.

Annnnnnd You do not have a 330 bhp engine. Maybe you have a 280 horsepower engine, but I would guess closer to 260. Annnnnd at the propshaft I bet you have maybe 250, which is no gonna push a 268 to that speed . . . There is absolutely no way this combo is gona run 46 MPH. No way, no how.

Trust us (me), we are not being wet blankets, we are trying to save you some frustration and some money. I am not saying she is right, I am just guranteeing that you did not go 30 MPH at 3000 RPM with a 13 inch pitch prop and a 1.47 ratio. Physically impossible. I mean impossible. You went farther (faster) than the prop could push through a solid. Impossible. Just not gonna happen . . . Do you have any type of fuel rate info? Another way to verify if your engine is running close to correct is through fuel rate. If you are making the RPM (you are a LOT closer than you think) and you are burning the fuel, then you are 99% of the time making the power . . .

 

[John_S]

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

Next thing will be to have the electronic fuel pump and carburator looked at ( It is a 650CFM edelbrock w/ vacuum secondaries )
Dan

If it is 650cfm, it is not a marine carb. Edelbrock makes two marine 4brls. #1409 = 600cfm and #1410 = 750cfm. Any others are street and can cause explosions in confined space. Along with model number, street edelbrock carbs usually have a large vacuum port in the front section of the base. If your engine builder supplied that, have them replace it with a marine carb.

 

[DanielADeYoung]

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

QC,

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.

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

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.

I await your reply

Dan