1977 Scarab 300 resto&tech advice needed.
 

Hello I am new here, anyways I bought my self a 1977 wellcraft scarab 300 a few months back complete boat with nothing missing from boat and with a trailer but not run for a while. I have just started doing a bunch of work to the boat in the past two weeks and would like advice as to what to look for, like I keep reading about transom stringers and brackets what is that about? Guy I bought the boat from said it had been done in the 80's but I want to know for my self, so how can I identify this, plus the boat is powered by twin .30 over 350's I just got done rebuilding the starboard engine, they are not stock engines, seller claimed they were 400hpx2 but will this move the boat fast enough? Again guy I bought boat from said it had 454's and 350's where put in when transom was done, are the 350's enough for this boat? I want to be able to go 70 MPH with this thing. Plus how to Identify my drives the are mercs but different from what I am used to and serial and model number seem to be faded away. Anyways any input knowledge or advice much appreciated.

Congrats on the purchase. Become a paying member and you can post pictures directly (it is well worth is especially having an older boat) How many hours are on the engines? I highly doubt that someone would change the engines from 454 to 350's back when the transom was supposedly done. Too much cost. 400 Hp is reasonable to get out of a 350 but not with 1980 parts. If the engines are stock to the boat they would be 260 or 270 HP. If the boat was not someones abortion case then it should have TRS drives on it with Merc transmission's. Do the props counter rotate? If they dont then you have a problem and either dont have TRS drives or someone stuck 2 of the same rotation on it, but they ALL came with counter rotating drives from the factory. To go 70 mph I would have to guess that you meed to make an honest 500 at the crank. Also check over in the Scarab section HBlair has a early 80's 300 that he has completely redone and had his share of headaches.
The Scarab 300 hull is the same running bottom as the Scarab II, Scarab Panther that was built until 1989. They are a great hull design but heavy layup from wellcraft.

Port engine has 328 hrs starboard had 337 hrs, I rebuilt starboard because of cracked block from improper winterizing, and will be doing the port engine next, I see what you are saying about 454 to 350's but there are things that catch my eye to say that they are not original engines, like the major one being the engine hatches have been ground down so they will clear the risers on the exhaust manifolds and shut. And yes props do counter rotate. And ok I will figure out the membership and post some pics of things.

Would you know if the stock to scarab 350's had steel cranks in them. Do marine gas engines tend to have steel cranks? I know steel cranks are a hot rod performance thing, helping you get more solid power to the fly wheel from what I understand. Anyways my motors got steel cranks in them and pistons look to be some sort of aftermarket. And the seller kept calling them Z28 blocks witch I have never heard of other then a Z28 Camaro obviously.
Pretty much all of my engine and engine building experience is with diesel pick up to large equipment engines. So forgive me if I seem lost I'm just not familiar with gassers in terms of all the different options and what not.

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Most of the old scholl small block upgrade motors i have seen are the high nickel 4 bolt units. Believe they all have the same casting number right behind the distributor.wouldnt worry about it too much but if you have 2 of those, then you can at least feel more assured the previous builder had some love.
a few minutes on the computer will solve your drive mystery .make sure they dont lean out from clogged siphon valves ,tank pick ups ect from crusty gas when your ready to take it out and put the hammer down

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Ok thank you will make note to check pick ups on tank I planed on removing all gas and filing with new anyways. And I just had carbs rebuilt.

Ok looks like I have Mercruiser TRS 330 drives.

None of the pictures will showed up

The only way to tell if they are steel cranks are to look at the parting line on the castings.
"The best and most sure method for recognizing a forged crank is to look for the parting lines on the counterweights. A forged piece will have a wide, irregular rough patch. A cast component (shown) will have a very sharp, well-defined line where the mold was separated" but ALL crankshafts are made from steel

The guy sounds like he probably thinks his quadrajet 350 with ram exhaust manifolds makes 600 hp with its 3/4 race cam. Anyways since you have one of the engines apart post pics and id numbers of the parts you have. You can make some good horsepower with a plain 350 but you have to tailor it to a boat and most car guys and engine builders have no idea on how to build a boat engine. Camshaft selection is crucial to avoid revision. Stick with the advice you get from people on here and youll be ok.

Ok I spent a little time wrote down all my casting numbers off the crankshaft, pistons, cam, heads, intake manifold, and block from my Starboard engine and Google the casting numbers and here's what I got:

Pistons: Keith Black Silv-O-Lite Hypeeeutectic 1479H .30

Crankshaft: GM 1182 Forged Medium Journal 3.48" stroke 350

Heads: GM 333882 1975-77 350,400

Intake Manifold: GM 346250

Camshaft: CMC 1539

Engine Block: 3970010 Trucks & High Performance Apps 4 Bolt Main.

Definitely doesn't seem like a 400hp engine to me.
So what's a good Build for both engines, to make at least 400hp per engine using the 4 bolt block, forged crank, and maybe even the Pistons that I have. The block is .30 over bore from standard bore witch I guess make these 355's. The boat is currently fresh water cooled at the moment, I bought 2 Identical heat exchangers from a 454 mercruiser and plan on installing on engines because I do want to be able to take her out in salt water. I will post some pics of my parts not sure why last pics not show they showed when I posted them.

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Im no expert here but I would look at Vortec heads and a nice roller cam and a hi rise intake. Arctic Friends or Bob Mandra can guide you further on what camshaft will work.

Ok thanks phughes69 I will look up those guys. And look at some vortec heads and high rise intake.

77scarab300, Ive got the same boat you do with the same engines in them, save mine aren't bored over. Where are you located? Would like to see how you end up setting your motors and props up. Im in the same boat (no pun intended) you are with upgrading power.

TruxtonFox: I am located in Bellingham Washington, and yes I will definitely share whatever info you need on my engine power upgrades when I get there just building funds at this point for parts and etc, probably start buying stuff and building this summer, it is interesting you have basically the same set up as I do in the same boat, did these scarab's come with SBC's from wellcraft, just curious now. I was told by seller that I purchased my Scarab from that it was 454's boat but got switched to small blocks, anyways what do you know about your scarab?

I hear ya on the rebuild side, I though about putting chargers on both but maybe wait till winter for that fun. I've got to rebuild a trim motor and put all new gauges on first. My understanding of the 77's was they all came with 350's, but in 78' scarab switched over to the 454. Not sure what guys like us can do to try and get a little more speed out of that little motor.

As far as my boat goes, it's in decent shape, transom and stringers are good and solid. I've got several gel coat spiders all around the engine compartment and rear of cockpit. Guy I purchased from had rebuilt both motors, but left old valve cover gaskets on and proceeded to run the port engine dry and spun a bearing. Throttles have been swapped out to mechanical transmission and throttle sticks. New upholstery in cockpit and sun deck. Triple axle trailer with front axle on surge brakes. I'll try and get a couple pics up today. Thinking about doing a wrap on it as well to try and freshen the cosmetics

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Nice looking scarab I like the color scheme, ok that is good to know did not now 77's were all 350's, I think there is a lot you can do with the SBC engines, seems like you can match big block power pretty close, obviously, and save a little weight at the same time, BBC has some good torque though but I was looking at stroker kits, like 383 stroker small block, basically 30 over 350 with 400 SBC crank shaft, you do have to do light machine work to bottom of block to get rod caps to clear due to the longer stroke have read this is good way to get torque and hp out of the 350, yes I thought I of the same as for as forced induction I think some roots style super chargers would be awesome poking through the engine hatch but awful expensive when you look at the kits X2, I own my own shop and business I do diesel light to heavy truck engine and truck repairs work on heavy equipment and fabricate things, I have built some really powerful diesel engines and used tuners to minipulate the engines so you can have the power when you want it, but save fuel when you dont, need it, thought some 6.0 PSD'S or 6.6 duramax would be awesome in one of these but marine gear for the duramax is very pricey and I don't think they make marine gear for the 6.0 PSD, plus I don't know how the transom and what not would like the extra 2,000ibs, so for now I am stay with gas, but back to forced induction you can always buy yourself a couple of Detroit Diesel 6v71 or 8v71 blowers and convert them to super chargers and buy the adapter for blower to heads, I have seen these detroit blowers sell cheap seems like a good way to save $$$ if you are DIY person. Anyways I was reading an article the other night on a 500hp SBC on pump gas build I will find it and post it.

Read my mind on the duramax stuff....I own a custom bus and horse trailer company down here that has a full fab shop as well. I think the plan for this season is to drop a new 350 in and call it good until the winter comes and then maybe twin duramax motors with standalone controllers. Doing that will have to swap out the old trs drives due to the torque. Detroit chargers is a great idea that I hadn't thought of.....nascar guys are making a reliable 800hp on the sbc, but I'm assuming for that kinda coin you would be able to do a bbc swap. I've got to keep telling myself that the boat is 40 years old and every penny is a penny lost.....don't wanna go broke yet lol

You will spend 2 to 3 times the money to convert a diesel blower over to gas. If you want to go the supercharger route keep an eye on the swap shop here or over at scream and fly forum. Have you thought about going the turbo route? If I could get my hands on one of these 30' Scarab cheap and had time to do another project I would put a pair of 6.0 LS engines in it. You can make 450-500 hp with a stock long block with a cam change and tuning to keep it EFI. There are a few threads in the general section of guys that converted to LS power. Think about it, a engine that weighs less than a iron headed 350 small block that makes big block power for less than what it would cost to build a 383.

+1

Nice project. Here's the link to my build on a 1979 Formula 255 Liberator: http://www.offshoreonly.com/forums/f...or-update.html

http://i705.photobucket.com/albums/w...ps0195b8ba.jpg

I caught a great deal on the "Built" 355's for mine or I would have gone the LS route. Iron head LQ-9's from 2003~2006 Escalade's and Denali's are plentiful and make GREAT power and TQ with a Cam change and a bit of tweaking.

The BIG difference maker in making power with the SBC's is the Vortec heads. I dyno'd over 400 HP and 400# TQ using Vortec heads and a Comp Extreme Marine Hydraulic Roller that is mild enough to have good dock manners but builds some serious TQ south of 4000 RPM...which is where you want it.

This might answer some questions for you...feel free to ask about any thing.

John

I may have more interest in the LS conversion, I'm assuming there is a standalone controller for these engines? What about coupling to the transmission? I've got a great running 6.0 out of a 2004 Chevy truck, would this work as one or are the Denali engines tuned more aggressively

Just wrote up all the details on LS Gen 3 swap into Gen 1, and what I know on TRS Drives and my experience at building engine mounts but for some reason my post never posted it just vanished, but anyways that link is a could start read it the crank shaft fly wheel flange seems to be key but I don't see why it couldn't be made to work on TRS

Yes...different heads and cam. The regular 6.0 in pickups is a LQ-4 I believe where as the Escalade/Denali 6.0 is the LQ-9.

Great article...thanks.