1987 Scarab1 21ft Help...

Barkus · 03-21-2009, 06:03 PM

Hi everyone, I just purchased a 1987 Scrab1 21ft. Has a brand new 350 crate motor in it. I think everything is stock. What prop should I be running to get the most speed? Also should I be concerned it has a Merc Alpha One in it? I hear some good and some bad about these drives. Any help would be great! Thx.

scarabman · 03-22-2009, 10:08 AM

The alpha drive should be fine behind a stock 350. As far as props go you probably want to run a Mirage Plus 23 pitch. You could also try a Lazer if you could find one. The diameter is a little smaller as I recall which woud allow you to go up in pitch without losing RPM.

Barkus · 03-29-2009, 10:42 PM

Hi scarabman and thanks for the info. I took it out today and the rpm's wouldnt get over 4000. My trim sensors are bad and i'm going to replace them, but I did mess with it at WOT and I could never get it over 4000.?.? I think my prop is a issue. Here is what is inscribed on it. (Precision Propeller Turbo M14 1/4 x 20 This can't be what I should be running to get top speed correct? Any advice or problems you can think of? Other then that the motor ran sweet everything seems to be ok but this issue.. The rpm's was always between 3800 and 4000 sometimes but no more than 4 ever. Water wasn't real choppy or anything. Thanks for any help!

spazboz · 03-30-2009, 11:14 AM

My friend has ab 86, and when he had his stock 260, he bounced between 19 and 21 pitch props. When he rebuilt the motor, he put vortec heads on it along with a nice cam and intake. We are guessing he is a little over 300 hp now and swings a 23 mirage on it. They are nice boats and a lot of fun, but I think the best he ever got out of it with the stock motor was 52 or 53..

Barkus · 03-30-2009, 09:05 PM

Thanks spazboz, so what should I try a 21? Wouldn't that give me even less rpm's then the 20 that's on there now? Scarabman says run a 23, will this boat with only 260hp spin that prop and not loose even more rpm's? Or, maybe my rpm's only max out at 4k is a different issue I'm not seeing..... It almost feels like my motor is working way to hard exp out of the hole, almost like a drag feeling. If I had a slightly bent blade would it cause this at all? Just trying to eliminate senarios. Thanks again for the help!

scarabman · 03-31-2009, 06:32 AM

Quote:

Originally Posted by Barkus

Thanks spazboz, so what should I try a 21? Wouldn't that give me even less rpm's then the 20 that's on there now? Scarabman says run a 23, will this boat with only 260hp spin that prop and not loose even more rpm's? Or, maybe my rpm's only max out at 4k is a different issue I'm not seeing..... It almost feels like my motor is working way to hard exp out of the hole, almost like a drag feeling. If I had a slightly bent blade would it cause this at all? Just trying to eliminate senarios. Thanks again for the help!

I take back the 23 Mirage. I was thinking 300hp 350. If you are only making 260 you definitely need to go smaller. As I had said earlier, especially given your HP, I would probably try and find a Merc Lazer. They are a slightly smaller diameter and would allow you to turn a little more pitch than a Mirage. No matter what, you need to stay with a 3 blade with your set-up. Ideally, if the motor is setup correctly you want to turn around 4600-4800 rpm.

spazboz · 03-31-2009, 09:04 AM

Barkus, it sounds like its time to do a little investigation. I wanna say with a Quicksilver 21 stainless 3 blade he was turning about 4500 on his boat when he had the 260. If he was going to do a lot of skiing or tubing he would toss his 19 on. I would say its time to inspect the prop and and maybe start looking at the general tune-up items on the engine. If its dogging out, check timing and fuel system.

Barkus · 03-31-2009, 09:33 AM

Ok thanks scarabman & spazboz. I will try and find a 21 lazer and see how it acts. Also I will tune it up and reset the timing and let you know how it works out. Thanks again guys! If you think of anything else let me know

Barkus · 03-31-2009, 10:14 AM

Ohh, I forgot to ask you guys one more question. I have that big whale fin on the back of my prop also. I know these boats have a issue with getting on plane fast. Could that fin be dragging me down you think? If I took it off how bad would it really be on getting the boat to plane out? Thanks again...

spazboz · 03-31-2009, 02:35 PM

Almost every boat I've ever seen these whale fins used on, have gained nothing from it. The last boat I saw it tried on was a 24 foot sea ray and he lost 2 mph on top and gained nothing anywhere else. With the acception of being a nice swim-step to get on the swim platforms, that's about all I see. The best thing Josh found to get his on plane was a set of 12x9 Bennet trim tabs.