Scarab 377 speed and stuff
 

Hey guys, hope everyone enjoyed their labor day weekends. I took my new to me Scarab 377 out last weekend. It has staggered 730hp blower 540's with 1.68 rstio speedmaster 3 drives with 28 pitch 3 blade props turning out. The best I could get out of it was 5000rpm (engines peak at 5700) at 70mph gps trimmed out in 1-2 ft waves with 5 people on board with half a tank of fuel with 2 coolers and overnight stuff. The boat seemed very bow heavy and didn't respond much to trim, breaking water in front of the windshield. That being said I've been told by several people to switch the drives and turn the props in to get more bow lift. I also have a set of 26 pitch 4 blades to try. Was curious what everyone else's thoughts were. Any advice is appreciated! Thanks everyone!
https://cimg0.ibsrv.net/gimg/www.off...847d9d3a1f.jpg

You're at 11% slip which seems really good. Don't know if you could get much better.
Looks like you're lacking HP.
What blowers are on a blown 540 with a single dominator?
Clean boat. Did you buy it in Jenison, MI?

Weiand 177's. Bought it just west of Jenison.

That's a really big heavy boat, in my 30' century with 620hp and SSM3's gutting the cabin really made a difference in how it would carry the nose. It seemed to hurt the balance in rough water but picked up a few mph in the light chop.

I don't believe a 177 is capable of making 730HP. Others correct me if I'm wrong please.

That's what the dyno sheets said, its getting bigger cams this winter, so i guess ill find out when it gets dynoed with the new cams. Regardless of what the engines make, my question was about the setup of the boat, not here to argue about engine power numbers.

The 177 is pretty small for a 540, the static compression must be high to start with. You should verify how much they are over-driven. 5700 rpm at max over-driven is too much.
The max I could squeeze out of stock headed 468's with 8:1 compression was 620.

I think the power numbers are relevant. The 177 is going to get really hot trying to feed 540s with any kind of real boost. That's going to lower power (especially in a hot engine room) and may possibly cook something. What kind of boost pressure were you seeing?

Like Rookie said, the slip number is good. If the engines are making 650-ish as installed in the boat, that may be about right. I would think the 3-blades would give you better bow lift but would depend on what the props are.

Nice looking Scarab!

That is a nice looking boat! I think your slip numbers are good and 70 is pretty respectable for a 37ft boat that likely weigh 5 or 6 tons?!!

The engines are currently running a little over 3 lbs of boost (from what the gauge tells me), the engines feel good like they wall keep pulling but just hit the wall at 5000 rpm. New blowers are out of the budget right now, just trying to work with what I have for now.

It's a big heavy full cabin boat. Bow lift might not be what you expect it to be without putting it on a diet. Turning the props in should give more bow lift. I believe adding cup to props will also give you more bow lift. More blades turning out might make it bow heavy (stern lift) and bow steer, but turning in should also give more bow lift. This is a staggered boat, correct?

I'd just enjoy it right now. I don't believe cams will do much. I'd save the money.

Not trying to set the world on fire but feel like it has more there in the drives/props.

Appreciate the insight! Yes its full stagger. I already had to change one of the cams since the original engine builder used the wrong distributor gear and it killed the gear on the cam. So I wanna change the other this winter so the engines sound the same.

Glass Dave’s favorite boat!!!

My 12 m runs 85 plus gps with NA 565’s SBS and sm3’s. Timing at 34 deg. 5,400 rpm +. 16 3/4 x 27 cleavers 3 b turning in.

last weekend was a little snotty in lake MI. Wish I could post a video somebody took 😂

edit:: BTW nice looking boat!!!

Is it really Daves favorite or is that sarcasm? Hahaha I'm out of Hammond, wind was out of the west so not a bad weekend for us. Where are you at?

We need couple more pics......:ernaehrung004:

Not a pro at these model boats but really like the look! I would have thought it could be much faster with 730 hp ! Were nt they running low 60 with stock 400 ish hp? I would have thought min 80 plus mph !

No for real. I talked to him about a year ago anbout some repairs and we had conversation regarding hulls. He loved those boats in rough water etc. Only sacrifice was the speed for known reasons but yeah his favorite at least what he told me.

NW Michigan, Manistee - Frankfort area

So back in the day I had a 38 Scarab flat deck with merc 475 turbo's that I modified by adding intercoolers and wastegates and upping the boost to a modest 6 to 8 pounds and the best I seen was 73 mph. I swapped the drives also and turning in was worse as it lifted stern but not the nose at all. Bottom had slight hook especially in chine area that never let the boat loose. Like you said water breaking north of the windshield. So the combo of the hook and the drives so low just kills this hull from any top speed. My friend back then had the same boat as yours (377) with staggered merc cyclone 400's and it was a 60 mph boat. He would trim up the drives until it threw a roostertail but the bow never lifted. The 30 Scarabs at least had some rocker to the bottom, I had a few of those.
Andy

Super cool boat, nice to see you got her back together and running! Mine's the same hull and about the same power. (650-725). But I don't have anything in the cabin yet. I checked the bottom of mine, and it's pretty flat. (one side has like 1/8" rocker, other side like 1/16" hook) You can see in this video even with the arneson drives, and props spinning in, although I'm not full throttle here, I'm not hardly toting the nose. With 5 adults, and half load of fuel, I think 70 is very respectable.
And it's true, Dave does like these old boats. :)

Well I do agree these boats are great in rough water, night and day from a 30 Scarab. I remember punching holes in some waves on snotty Lake Huron blowing a northeastern while sipping a beer.
Andy

awesome looking - there use to be one down in spring lake / grand haven back in the 80’s and early 90’s same color scheme called “temptations”. I’ll never forget that boat as I would be drooling all over every time I saw it. 👀

Bill Lawson at ateco engines near chicago has a 377 raised deck scarb named dazzlement. Super cool old boat. Same style as yours. He may be a good person to talk to. He's had the boat a long time and is gonna try to get it back in the water for next season. Here's a picture of his boat. There was a monogram model sold with it's likeness back in the eighties.

I looked at buying "Temptations" back in the day. Probably 2003ish.

I used to boat a bunch around the early 80s on lake Macatawa in Michigan in my 18’ Baron which radared by Mercury was 58 mph with a 260 alpha package.

Van Andels of Amway had a 377 with staggered 400s that I could walk away from slowly if that tells you anything .

Year later they had another 377 named Warp Factor with triple 370s. That boat was actually slower than their twin 400 boat.

If you listened to it from the bay it sounded like it was going a 100 it was so noisy.

Big heavy boats with heavy cabins and deep drives.

3psi on 540ci tells very little about how fast the 177's are actually spinning.
As far as whether they can make 730hp depends on what the engines make N/A. The 540's probably would make 600-650hp without the blowers.
Measure the diameter of the top and bottom pulleys to calculate how much they are being overdriven.

I think a pair of 1071’s with 5 pds of boost would help get that condo up and moving.

Actually just a well built 540 NA platform be the ticket!

That’s one where you just put a reliable package in and go. Let the go fast boats pass by and just wave and at the end of the day you’re still on the water enjoying your time and boat with the hatches down sipping on your favorite drink 🥤

​​​​I can't leave well enough alone. I'm gonna be hunting for more mph. Bigger blowers or pro chargers are definitely on the future mod list. Also extension boxes, if I can find any.

I get it trust me BUT don’t forget my advice! I don’t listen to my own either so I should just shut the fk up! 😂

I built that model! I totally forgot about it until I saw your post

I won't forget it. I really like this boat and I would like to hold onto it for a while. I always wanted an old wave-crusher and was hoping to go 75-80. I know there will always be faster boats out there but I really like 80mph haha

Hahaha, right now you want 75-80 then it`s 80-85 then gotta get into the 90`s!
Its a disease and we all have it!

My friend has "The Preacher" 10 meter Fountain across from my slip, I'll just ride with him when I wanna go 100mph hahaha but yeah you're right.

Really nice clean 377. Great find.

177s as you know are pretty small for a 540. But it will probably get you over the hump of performance. The 177s have a peak rpm of about 15k, but that is totally maxed out.
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Lots of good threads on here about 177s. They can push some air, and coupled with modern head and cam tech, they are better yet.

There is a limit where the heat generated by the blower at the limit, will super heat the air to the density where it would be the same NA or worse off. You still have the parasitic losses.

When the blower cases get heat soaked...they will open up the clearances...making them less efficient. So a dyno pull is not the same as a sustained run at close to or WOT.

Reading the B&M Magazine data book from 1990, they really did a good job of dialing in their 420s with the twin rotor using teflon strips and good rotor design. The twin opened up some volume compared to the triple screw roots, why they are considered a 7-71.

Some prop changes can make a world of difference. Bblades can help with that.

Weiand 177 max rpm is 13500. I spun mine to about 12500rpms on my 525SC.
If you're spinning it 10k+, its best to change the lube every 20 hrs.

Glad to see you were finally able to get your boat in the water. I would try those 26" 4-blades as long as you have them. They just might raise your RPM's a little more if the engines actually make peak power @5700rpm---not saying they will get you to 5700rpm, but maybe more than the 5000rpm with the 3-bladed props you already have and see what happens.

I mean, you might as well try those 4-blade 26's----so put them on, give it a whirl and let'r buck