ACrooks69

iTrader: (1)

I have a 20" Searay 185 with a warmed over 383 stroker and the alpha drive. The motor already made in the neighborhood of 415 hp (383, 10:1, Trick Flow Twisted heads, Performer intake, JET stage 2 quadrajet, Kodiak Alum Manifolds, Comp Cams Xtreme Energy street grind HR264HR 212/218 Hyd roller cam with a 110 LSA) and the boat went around 73 MPH turning the motor at 5100 RPM. Last year I ported the TFS heads and moved them from 227 CFM @.500" lift to 258 CFM. I also bumped the grind to an Xtreme energy Marine XM276HR roller cam w 224/230 degrees of duration and a 112 LSA) I tried a RPM intake with dismal results and the boat actually went slower and would bog/pop on takeoff. The boat which would go 71 or 72 with 5 people will barely go 71 by myself. I also have an exteme lead condition even with jumping up to AX metering rods (from DA) on the quadrajet. This was not a problem with the smaller cam. Fuel pressure is good and the secondaries are opening up all the way. Tried an 800 Edelbrock and tuned the fuel in good and still had problems. The only thing I can think of is the restrictive transom/prop exhaust. I am going to yank the reversion baffles out of the y pipe to see if that aids flow but thats about all I can do. It would be an extreme pain in the azz to put thru hull exhaust on this baby with the way the engine is mounted and the swim platform is located. I know I just thru a lot out here but I am laterally banging my head on the wall trying to figure this out. Is it not practical to try to flow 450+ Hp thru the Y Pipe.
One other thing I could to is install the exhaust bellow cutout kit that I heard of years ago. I think the seals the exhaust bellows when trimmed down so exhaust will go thru the prop, but comes apart when trimmed up to aid in exhaustion.
If you guys can actually sift thru this pile hear any help would be appreciated.

MnFastBoat

I am no master by any means but I will say it sounds like you have done alot to get hte air flow into the engine, now you just need to let it breath it out
Open up your exhaust on the bellows will help some, but not on plain.
I would not totally suggest removing you y-pipe flappers unless you NEVER ever leave the boat in the water with the engine NOT running. They are designed to prevent back flow of the water. And iwth a cam such as your your firts fire could possibly suck hte water right up.
Not sure of your year, but the older Searays had the water boxes in the exhaust exit. Does yours? these models exited on the transom corners. I know of two done like this and they removes the boxes and went through hull there. Maybe worth looking into to copy. I know the Pachangas were like that.

Let it breathe and you will next be needing to upgrade your drive away from that alpha.

Do you already have external Hydrualic steering? With speeds like that and a small hull I would not want to be in or around your boat when the unthinkable happens

good luck and keep us all posted.

BTW, WELCOME!

ACrooks69

iTrader: (1)

Thanks MNFAST. The model year is 1991 and unfortunantly I do not have external steering. I am not familiar with the term "waterbox" could you eleborate. The Pachange 22 is going to be my next step up if I can find a decent one.
Were you saying that exhaust bellows cutout does not aid when on plain or getting to plain?
The boat is typically trailered to the lake and taken out daily. I may sit in the water overnight like once a year, but it doesn't have to. Taking it out is not a problem at the one place.

mcollinstn

Bravo 1 figures below:
Rule of thumb is 375hp generally doesn't benefit from thru hull.
Above that figure, you should theoretically benefit a smidge.
425hp is about as much as you'd ever want to pump thru the lower unit.

I have no feel for Alpha flow capabilities, but would imagine them to be a bit less.

You've ALSO cammed the motor for a 5900 rpm power peak. Prop accordingly.
Hopefully you didn't RETARD that cam any, and in fact you'd do yourself a favor to set it at 4 degrees advanced. Your weak/popping low end suggests a lack of adequate vacuum signal.

And, by the way, you are asking a lot of your Alpha, and should use a drive shower and 15 hour lube change interval on it and keep a lookout for sparkles in the lube.

ACrooks69

iTrader: (1)

Put a Shimrik Drive shower on 2 years ago after I blew the drive. Can't say enough about it man it works great at keeping the drive cool and no more chalky white on the drive. That gear lube gets changed quite often, but I know I am living on borrowed time with that drive. I know I degree the cam in, but I forgot where I put it. I think I advanced it 4 or 5 degrees. I can always check it when I pull off the front cover to fix an oil leak. I tried a Mirage 19" pitch yesterday and spun it up to 5600 RPM. The normal prop is a Tempest 21. The Mirage lifts the boat to high out of the water and it starts pourposing. I tempest does a good job, but that picks it up a tad to high also but its the best MPH prop. Cleavers didn't work well on it either. The vacuum signal is good I think it is just jetted to lean on the primary side. I'm going to have to play with that. Funny thing is the surge only happened with the RPM intake the standard performer didn't have that problem. And with the prop venting to 2900 RPM I would not think vacuum would be a problem at the point. But If I new every thing and had all the answers I would be coming here, so I can't rule out anything.

ACrooks69

iTrader: (1)

One added thing with the lean running condition. Could the restrictive exhaust be causing the lean condition. If the motor can't get the exhaust out before the valve closes, that would create a lean condition since it can't take in a new full charge. It would kind of be like an EGR valve right?

Badtoon

ACrooks69

You got to let me know how the Alpha holds up. I'm sending 300 and change at mine and already have a halo drive shower and switching to Redline gear oil. If yours holds up I'll step my HP up some more.

ACrooks69

iTrader: (1)

I wouldn't worry about 300, we had around a 330 hp setup from just about the getgo in 91, it wasn't untill 99 when we put the stroker motor in that we started having drive issues. I ran royal purple in it, but switch back to Merc High Perf. But like I said earlier in the post, it didn't hold up. But then again the shop that rebult it said it had about the number of hours on it that they start to wear out. I personally think the gear lube wasn't filled up high enough. (My fault) and the top gearset ran all of its teeth off. We didn't have the drive shower at that time. The upshot I like with my boat is it's fairly light at about 2500 lbs so that should stress the drive a little less than with a 4000 lbs boat.