Thread: New 383 Stroker engine will not rev.

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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..