New 383 Stroker engine will not rev.

I had a 383 Stroker built for my boat. 4 bolt block,All new parts,including SCAT crank,KB Forged pistons,H Beam rods, Comp X treme energy marine cam,Dart iron Eagle heads, Etc etc. Engine builder is very well known and respected for his work, A very detail orientated guy. Very careful and extremely knowledgable.
I asked for a 400 Hp max engine ( To save my outdrive) that would run on 89 octane. ( Lake Gas). Eldebrock ESP intake and new 800 cfm Carb. Electric Fuel pump, New Accel HEI ignition.
Here's the catch. Engine starts and runs like a watch (Everything was balanced) Excellent throttle response. Pulls this Approx 4000
lb. boat up on plane in a flash. BUT it will not rev past 4700 rpms.
Builder say it should easily pull to 6000 rpm. timing is set at 12 advance initial 36 max. Dist, only has 24 degrees built in. No detonation. Plugs read as they should with no sign of lean or rich.
Tried primary voltage jumper to check ignition. no improvement,
checked carb linkage for full open. Fuel pressure is reading 1 1/2 lbs. at WOT. I've spent 2 weeks on the phone and trying to sort this out to no avail. I have approx. $7000 spent in this entire engine build and install and the boat runs about 6 mph faster than last season with a whipped 350. Any ideas will be appreciated.

What happens when you reach 4700 does it seem like it lays over? How strong is it pulling ? Do the revs climb quickly up to that point and just stop or does it just work up to 4700 slowly? What valve springs and lifters are you using and are the springs set at the correct height? How did you adjust the lifters? 1.5 pounds of fuel pressure at WOT seems low to me. I would think you would want 5-6 pounds. What diameter fuel line are you using? How about the exhaust? Is it above transom or below? Have you changed props? And my last question is what sort of RPM did the old motor pull?

Pat

With the old engine 4000 was the max., but it was a thrown together rebuilt 350 and we know the ignition system was scattering all over after 4000. It pulls hard and fast to about 4000 and then as you trim it up it comes up to 4700. The eldebrock book on he carb says it should have minimum 2 lbs. residual at WOT and I did order a new bigger fuel pump. It now reads approx 1 1/2 lbs at WOT Before approx 18 inches of line and a filter. It's 3/8 fuel line. I thinking that fuel at the carb may be below 1 lb. The new pump is rated 76 gph @ 5lbs. Exhaust is Mercruiser stock , not through hull.. Right now I'm running a 19 pitch 14 aluminum, It's my spare. I have a 19 pitch stainless out to the shop for cupping and venting. I tried a 21 aluminum and lost RPM's and speed.

whats your compression? you also say dist. as 24 degrees adv. built in. Is there a vaccum adv. ? sounds like timeing to me but i also no nothing of the characteristics of boat motors but cant be much diff.

Ok the better pump is coming. The fuel filter that was installed is just a small metal can. Are you saying to crank the initial timing up even beyond 12 degress ? There is no vacuum advance. I do have the timing curve set to come in at 600 and full at 4000 . I asked the engine guy why he wanted it set that way and he said for smooth acceleration. Should I speed up the curve with lighter springs ? Besides listening, How do I know how far I can go with timing without damage to the engine. At 12 initial we have no pinging or detonation. Comp ratio is 9.5-1 I will settle for less ooomph to insure longevity. All the boat people I'm asking are saying 34 to 38 degrees... Something is holding this engine back.
A stock 5.7 mercruiser engine will run out to 4600-4800 I could have put a rebuilt crate 350 in it and had almost the same performance.

I's still say it's the prop although the fuel pressure does sound light....I had the same problem in my boat after building a hot 350. As soon as I got a properly pitched prop it really woke up. I'd say 21 degrees minimum with that motor. Thats what I'm running on a 21 ft stingray with a 350 horse 350. It will get up to top RPM slower but won't cause the cavatation (Air space behind the prop) that a lesser pitch causes with a high HP motor. I tried the stock 19, a 21 and 23. Off course then I smoked the outdrive. Hey guys look it's some kinda silver gear oil in there. No man that's gear soup. What kind of hull are you running?

23 Ft Chris Craft Scorpion, It's a heavy boat. But I have a friend with the same boat. Was running a built 350 in it last year and it ran out at 67 mph. running a 19 pitch stainless, Cupped And vented. But of course it would tach out to almost 6000. All I was looking for was Approx 55 mph. Engine was not dynoed, but builder is claiming conservative HP at 375 and torque numbers higher. If I can get the boat to run at 5500 max it would give me 55 mph. with the current prop pitch and slippage. When I get the stainless back from being worked I 'm sure it will help, but if the engine won't tach out to where it should obviously the boat won't perform as I was hoping. I'm not a racer, but I've got a lot of money invested in a boat that goes 5 mph faster than it did before I invested it. I tried a new 21 pitch, lost rpm's and speed.

Just spoke to the engine builder, he says no more timing. He's claiming that I may need to drop the timing back a few degrees. He said when he tunes boats on the water that sometimes less max timing will give you a higher RPM. KB pistons are calling for a max of 34 degrees for the forged pistons is the best. Cam is supposed to run to 5500 max.

Boat has a spark arrestor, but no Air Filter, I guess they function as both. I will check that also to make sure it isn't obstructed. Looking at Accel's page and my dist. instructions I am going to lighten up the springs Should come in about the same RPM , but be all in at 3000 instead of 4000.. I guess I'll just have to experiment and see what works.

why doesnt your engine builder have his bikini on and is sitting next to you when you do a pull? He's the most familiar with the motor and should be able to help......shouldnt he?

If not, toss him over.

has anyone thought about windage in th engine check the pcv system you might have a bad pcv valve?

well, it's pretty obvious that the motor is running out of fuel.

Order a #1466 needle and seat kit from Edelbrock. It's 0.110" and will flow more fuel into the bowls. Also order a Edelbrock #1791 electric fuel pump and run 1/2" lines from the tank to the carb. The pump is pre-set at 6 1/2 lbs, so no pressure regulator is necessary. Tee off an electric fuel pressure gauge right where the fuel line enters the carb and monitor it under full power.

http://www.edelbrock.com/automotive_...mps_main.shtml

http://www.edelbrock.com/automotive_...hun_perf.shtml

I am upgrading the fuel pump and filter. I am also going to check for exhaust restriction. I was going to install thru-hull, but I left the exhaust stock. Changing advance springs to the medium springs instead of the heavy ones. According to Accel the heavy springs limit the advance to 20 degrees, so I'm at 32 max. Curve will come in a tad bit sooner and be all in by 3000 instead of 4000. I'm going to just tinker here and there until I find the culprit. I have access to 4 inch. thru hull fittings if I find a restriction.

Thank You all for taking the time to reply to my RPM woes. I will be moving up the timing curve and installing a bigger fuel pump this week end. We'll see what happens. I will also be checking for
exhaust restriction. Again Thanks guys.... Denny

Installed new bigger fuel pump,moved curve to 600-2800, No change, Runs real strong to about 4800 and just quits..

Try a prop with less pitch, let it rev past the flat spot. Not a real fix, just a test.

Cam comes in at 1350 -5500. It seems that we are at an impasse. Motor builder says now. ( I guess thats all it's gonna do)
5200 on a shop tach is the best that we have seen. I'm thinking that although the boat runs much stronger than it did before. Much quicker to plane, and I can stay on plane at a lower RPM than before. Will plane off with 4 adults in it now as compared to last year when you had to move everybody up front to get the front end down. Boat design is rear heavy and all the scorpions I've seen lay low in the water in the stern. I guess I'm just gonna wait for the cupped and vented stainless 19 pitch to come back from the prop shop and see how it works then. My son blew the upper gearcase on his boat last week end , so any extra funds are going in that direction right now. A Friend's Scorpion will run out to close to 70 mph. but his motor was dynoed at close to 600 Hp. Has to run 93 and the friggen thing has no idle. Docking the beast is almost impossible unless you paddle it in.

Installed a new stainless 19 pitch and had it cupped. Boat runs very strong and quick for it's size up to about 4700 and thats all there is. Same stuff. A little faster with the new prop, but still won't rev past about 4700.

Get your engine builder to re degree the cam.

What does the manufacturers specifications say? You need to talk to the factory about this and have them send you the specifications in writing if you don't have them already. Don't ask the local guy that rebuilt the motor because according to your postings he is telling you two different stories. First he tells you that you should get 6000 rpm then tells you that it is set up for max of 4000. Well, which one is it?

You are talking about two different things here, rpm's and speed. In the boating world these two things aren't necessarily related. There is no transmission except F-N-R and no rearend gearing to consider. There is a gear ratio consideration in the lower unit, but it shouldn't vary that much. Speed has to do with trim position, how clean the hull is, weight, and of course the prop. The aluminum prop is going to perform differently than the SS prop because of flex in the aluminum. Anyone can make your boat hit 6000 rpm, just drop down in pitch. But you won't have the top end speed and you'll spend a ton of money on fuel. Boats are kind of like running a car with one gear (prop). You can prop it for low end performance like skiing of prop it for top end speed.

If you want speed go up in pitch and use a ventilated prop to get you out of the hole. Get one with different size plugs (usually a set of three) and test them. Also, most dealers worth their salt, have test props and will let you try them if you plan to purchase from them.

I say, check for fuel restriction. Line is either to small, kinked or pinched, or filter needs to be one of higher capacity That small filter needs to be pitched and the fuel tank pickup should be inspected. Also, is this motor broke-in yet?

You have a lot of excellent suggestions in the replys to your question. I have one more. Don't make too many changes at one time without testing the boats performance as you go. Change one thing and test and so on.

Good luck!

Engine may have 5 weekends of running on it. Out of that maybe a total of one hour WOT each week end. Fuel pump now delivers at 5 lbs. WOT. 3/8 Fuel line. I was thinking fuel problem , but plugs don't read lean. I've tried direct ignition jumper, in case of wiring problem, but it made no difference. I tried a new 14 X 21 pitch aluminum, but it didn't work as well as the 14X19 lost RPMS and speed. The engine just seems to run right up to about 4700 and then thats it. Runs strong at WOT , just won't rev any higher.
I've fiddled with the trim. With the boat trimmed up just to the point of starting to porpoise just a tad and then a very small trim back. Frigen thing seems to be flying , but the speedo and GPS say something different. Does anybody know if a dolphin on the lower unit will slow me down ? It certainly helps getting up on plane in this tank. This boat also has anti-fouling paint on the bottom from it's days in the salt. If it would rev to 5500 it would go 55mph. Thats all I was ever looking for. My friends Scorpion will run out to over 70 mph ( radar clocked) Same Boat, Same hull, Maybe 500 lbs. lighter. But I'm at around 400 Hp and he's close to 650. He's also running a 14X19 Cupped stainless, but his motor will rev to 6000.