Speed
 

:whistle:Whats up guys! So I am wondering if I'm nuts or what.... After running the boat this past few months with the new motor( chevy 496 and basic carb tuning, holly 850 dp 79/83 (stats on engine Scatt 638 rods/ 9:25 forged/ Scatt steel crank/ 502 rec port heads/ Rpm air gap/ crane cam Hyd flat 571/553-236/246@50 with a 114. Stock manifolds and risers with custom insert tubes (water) I have not been able to get past 5200rpm and 66 mph with a 24 Mirage 3 blade in 1 to 2 footers. I was estimating 500 hp but I think I might be well short. Fuel press is 6 psi at wot. After talks in here I dont think the manifolds are hurting me a whole lot but I think the motor should pull at least to 5700 the a 24 ? any thoughts? I am thinking about putting a 1 inch spacer on the intake and trying it this Friday for the last time this season.
Boat is a 1988 Scarab Concept 23ft 3500lb boat, small step in hull (1 1/2 inch) 3/4 of the length back

ignition system???

Ign system is good. 33 full advance. I did bump it up to 36/38 put plug readings were showing a bit of splatter from the pistons so back down to 33. On gps, flat water, 62 mph is just about it.

How deep is the drive? Trying the spacer is a good idea. It's cheap but unlikely to add more than a mph. Check your hull bottom to be sure it's straight.

Did you have the prop checked to see if its true to spec? I had a set of 25's for my old scarab.....one prop was decient...the other had two of the three blades off by one complete pitch! One was at 24 the other was at 26!

Ok, So lost 2 mph with spacer. Didn't have a chance to jet the carb up but checked # 5 and 7 plugs and looked good. Bigger problem is oil STILL STILL STILL getting dark after a few hours run time. Thermal temp gun says 190 at oil pan and fittings into remote oil filter sys, cooler after exchanger by 20 . Right where it should be!!!!!!! WTF!!!!!!
170 static cyl pressure on all eight.Fresh motor 20? hrs. HELP!!!!!!!!!!!!!!!!!!!! I'm thinking because of low compression (9:25/1) reason for low rpm 5000/5200. Cam spec called for 10:1 min. This engine is running damn near what the old 496 ran with peanut heads and stock low rise intake! I need a beer..............................

Looks like lack of fuel (jetting) and lack of timing might be the issue. Was only at 30 full advance. Way light.

Checked timing today. I have a 24 degree mod. I was at 8 base/ 32 total. Bumped it to 14 base/ 38 total. Going to change jetting to 83/88. Throttle response is WAY better and fires up as soon as I hit the key.
Started fine before, just not as quick. We are gong to have a few days close to 60 here soon ao I'm going to try it out and hope for the best! ( MORE SPEED ) What are your predictions?

Hey Wally, Didn't get a chance to get the props labed but I will do so. After making my timing adjustments if I don't see a gain I'm gona call it quits till I get new manifolds and risers.

I think your short on your 500hp goal with the stock manifolds. I have basically the same engine but a 468 and not a 496 and a smaller cam Iskey 270/280 mega and 1.7 roller rockers, I went with that cam due to having stock manifolds and not wanting to have reversion problems. I was looking for 450hp on the dyno when I built my engine. My engine made 407hp/460 torque on the dyno with headers but I bet it only makes 365hp in the boat with accessories and stock manifolds.

Lots of people estimate what their engine build will make but not many pay the money to dyno the engine. I payed for the dyno to make sure my engine was broken in and tuned properly but I also wanted to know how good my build was.

Get some good exhaust and let that engine breath!

Might pull the engine this winter and have it put on the dyno. Going to see what happens with the jetting and timing. It it helps it will only be a bonus when I get my new exhaust.

Weather is going to be great here today. Just about 65 degrees. Going to see what happens with timing and jetting.

Ran the boat. Timing helped a bit. The water was dead calm with current. Not good for going fast. Hit 60 AGAIN!!!!! :lolhit: Pulled plugs looked lean/ even with 83/90. Ran best with 83/85 with 36 deg total. In 1 footers I figure 64/65. Same as before. Taking the carb to Nickerson Performance in Bristol, Pa tomorrow. Talked to him about the issues and said he can make it better. We will see. Did a static chk on the cyl. All are between 170 and 180 psi. At least nothing is hurt there.

You need to tune jetting with a air/fuel gauge ... thats the best way . Reading the plugs with the new fuels is tough. Your going to have to install a o2 bung before the water in your exhaust system. If you decide to dyno the engine give Tim Jepp a call @ 856-589-5658 ... he has tuned my last 6 engine builds and is local NJ . In my opinion your engine is down on power . My last n/a 496 made 606 hp @ 5700 ... 731 hyd roller installed @ 107 ... oval port 290 edelbrock heads ... rpm airgap intake . 9.6 to 1 compression and a custom 1030 cfm 4150 carb built and tuned by Tim . The key is in the tune and I have found dyno time to be well worth the money and time invested .

Took the carb to Nickerson's today. Great guy! They request you bring a completed engine and boat spec sheet from their web site prior to going. Dean (owner) took time to talk with me about my issues with the boat. I took my spark plugs with me and that helped. My carb HAS ISSUES! Going to swap out my stamped rockers for rollers and put the carb back on next week. Hope to see an improvment.
Thanks Jetmech for the heads up on Tim Jepp. I'll call him.

You need a new intake. The factory intake is all done at 500 hp power level. Look for a Mercury 500 style intake. Factory heads are hurting you too.

Wannabe

Ditto what JM said. That exhaust though will totally kill your scavenging which is necessary n/a and with rect port heads. Pretty much any aftermarket manifold would be an improvement with a full length header like an eickert getting you the real pop.

BT

Pulling the engine this week to take it to be put on the dyno. I will be able to be there and work on my engine along side Dean Nickerson. This should be fun!!!!!!! Keep you guys posted......

Carb is done. Picking it up tomorrow. Friday weather looks good. Going to go for a spin and see what the carb upgrade does. Watch me go slower..........:lolhit:

Pull the engine next week and dyno it, also going to install a set of 1.8 roller rockers

The carb looks great! Milled off the air horn, adj air bleeds, port and polished, etc.....Ran the boat today and saw a nice improvement. Picked up 2.5 mph on gps and just about 200 rpm. I did have the 1 inch spacer on today. ( the spacer cost me mph with the old carb set up ) It now pulls all the way up to 5000 rpm. If I had a 23 pitch I would have tried it and gotten a bit more speed and rpm but all things considered ( my stock exhaust holding back a few more mph) it was a good way to end the season. I ran out of time to try running it with out the spacer. Who knows, maybe it still cost me mph.

So Its going to be almost 60 here tomorrow. Going to run the boat with out the spacer one last time this year. I'll let you guys know the out come.......

No update guys. Was on my way home from getting the car serviced and the wife called. Broke down near our home. Pulley on the belt tensioner. Replaced all 3 and new belts. Not fun on a BMW MRoadster.
:stooges:

Dean always told me his carbs pull harder on the top end with a 2" spacer . After having two of his Stage V's i believe him . He is a great guy to talk to and set me straight on a few things in the marine engine world . I hope your setup works out well .
PS : Don't you just hate working on stuff because it's broke . Completely different if your wrenching to make it faster .

With out a doubt......