Hello/Intro and Sea water pump pickup location question

kpforce1

Cadet
Joined
May 5, 2017
Messages
22
Firstly, hello all. I've been an iBoats creeper for years but just recently joined up. I figured I'd give a little info on my current project. It is a mid to late 90's Maxum 2000sc with a balance shaft 4.3. Since I will have a new motor and exhaust setup already, I opted to go for a freshwater cooling system (run boat on the river anytime of year). I have the appropriate crank mounted Johnson sea water pump but I stared wondering about the water pickup options.

Most people would say just do a thru hull or transom pickup and I was leaning towards a bobsmachine transom pickup and a strainer but I started wondering...could you remove just the impeller from an Alpha 1 (gen I or II) and use the existing lower leg pickup for the sea water pump similar to the Bravo units? After looking at it I don't see why this couldn't work even if I needed to mod the inlet holes a bit. Has anyone ever done this or known someone who did?

Also, the boat was originally equipped with an Alpha 1 Gen II but currently has a Gen I unit on it (I know lol). I'm going to replace it with a 1.6x ratio unit more than likely. I got the boat for free so when the 4.3 spun a main bearing during the "testing" phase I didn't hesitate to pull and build it. I wanted v8 type power but better fuel economy for cruise so I did the following for anyone interested:

-block .030" over
-Proper quench distance/area attained by: a.)block deck .005" piston in hole b.) .040" Cometic gaskets c.) KB 12cc dished pistons (quench area matches Vortec chamber)
-ARP fasteners on rods/mains/heads
-Vortec heads with stainless valves (2.02" intake and stock sized exhaust), appropriate radius and valve job, milled to ~61cc, port matched to intake mani
-Comp beehive 918 springs and appropriate retainers (heads machined for them and over .500" lift cam)
-ARP 3/8" threaded rocker studs (my heads had the M10 sized threaded holes)
-Went with an Erson cam grind after talking to their guy and learning about the lobe profiles they use (flame suit ready as 99% of people here are going to tell me my motor is going to suck water etc. etc.)
specs: Duration ADV - IN 282*/EX 286* @.050" 214*/218* Lift .480"/.510" Lobe Center 112* w/4*adv.
-Comp 1617-12 Ultra Pro Magnum 1.52 roller rockers (self aligning)
-.080" wall pushrods
-melling stock pressure/volume oil pump
-lighter weight timing set
-Performer 2114 intake with 1409 carb (1485 jet kit installed with a full jet kit to dial it in on water) and heat soak preventive gasket
-Sierra 18-7232 hi perf. flame arrestor
-Marine Power high flow exhaust manifolds with 3" riser spacers to provide some addition distance to combat possible reversion
-newer style y pipe with better flappers and longer pipe elbows (cobra headed looking type) for the 3" riser spacers
-exhaust tube vs bellows
-Thunderbolt IV with Moore Performance E-core coil and using .060" plug gap
-Mercury Remote oil filter kit (because it makes life easier lol)
-new circulating pump


Thanks,
Kp
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
(run boat on the river anytime of year).

Ayuh,..... Welcome Aboard,.... Ya still gotta drain the raw water side in freezin' weather,....
could you remove just the impeller from an Alpha 1 (gen I or II)

Donno,.... Never tried it,.... I'd just do a thru-hull into a strainer,.... or a screened thru-hull pick-up right into the pump,...
the boat was originally equipped with an Alpha 1 Gen II but currently has a Gen I unit on it (I know lol).

What else was changed, besides the drive,..?? lota difference in the shiftin' parts in that swap,....
Duration ADV - IN 282*/EX 286* @.050"

Sounds like a nice build,.... time will tell whether the cam is to big,....
 

kpforce1

Cadet
Joined
May 5, 2017
Messages
22
Ayuh,..... Welcome Aboard,.... Ya still gotta drain the raw water side in freezin' weather,....


Donno,.... Never tried it,.... I'd just do a thru-hull into a strainer,.... or a screened thru-hull pick-up right into the pump,...


What else was changed, besides the drive,..?? lota difference in the shiftin' parts in that swap,....


Sounds like a nice build,.... time will tell whether the cam is to big,....


Thanks Bondo.

I will drain the raw water side in freezing weather for sure and the boat will get winterized appropriately. Is there a particular thru-hull and strainer you would recommend? When I was looking around it was hard to determine what would be the best option. Also, for the thru-hull, what seacock should I use?

The drive was replaced before I ended up with it. I didn't know until I bought my anode kit that it was a Gen 1. Previous owner had a shop do the work but it looks to me like they replaced everything from the gimbal ring down along with using the gen I trim cylinders. I thought the only real difference in shift linkage was the upper shift shaft in the bellhousing due to the different fork lever design of the Gen I and II. In my case, it has a Gen 1 bellhousing so there wouldn't have been any voodoo required aside from adjusting the shift cable to throttle actuation for proper engagement (which I did).

As for the cam, yes. I opted for stainless valves as a precaution along with better flow (much better valve design). No one ever does anything out of the box on the 4.3 (or most marine applications anyway) with cams etc. for fear of the potential cost of killing a motor. I understand that but I think I have taken the proper steps in greatly reducing the potential for water reversion. With the addition of 3" riser spacers, longer exhaust elbows, better flapper design, and the MP Manifold elbows have a very nice anti reversion ramp. I'm pretty sure I shouldn't have any issues. I'll do plenty of idling tests to see if there is any reversion at marina/docking speeds.

I considered putting it on an engine dyno just to see what it makes lol. It should be a very stout 4.3.
 

kpforce1

Cadet
Joined
May 5, 2017
Messages
22
Anyone else removed the water pump impeller from an Alpha I drive and used the drive as a sea water pickup? Anyone? lol
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
It will only work if the crank mounted pump is self-priming. That I don't know.

Why risk it when you can add a proven thru-hull.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
Leave the impeller and just cut the hose at the transom side, The impeller pushes the water , to suck water you may have a suction leak sucking bubbles.
Thru hull and strainer is the way to go, just remember to use wire wound hose . regular hose will collapse under the suction
 

kpforce1

Cadet
Joined
May 5, 2017
Messages
22
It will only work if the crank mounted pump is self-priming. That I don't know.

Why risk it when you can add a proven thru-hull.

The pump I selected is the Johnson 10-24805-01 (F6B-9) and is self priming.

Leave the impeller and just cut the hose at the transom side, The impeller pushes the water , to suck water you may have a suction leak sucking bubbles.
Thru hull and strainer is the way to go, just remember to use wire wound hose . regular hose will collapse under the suction

I would use the proper hose for a suction application and ensure all hose connections were air tight. I may just try it and see if it works lol.
 

kpforce1

Cadet
Joined
May 5, 2017
Messages
22
Well, I finally got to take the old girl out last weekend for break in. Unfortunately I was limited by the crappy gas I had to deal with and could only give it less than 3/4 throttle. With a 1.8x drive and 23p aluminum prop i could cruise at 40-42mph on pretty rough water at 4000-4100 RPM. Any more throttle to start opening the secondaries on the 4 barrel and I would start getting ping. With some real fuel and some fine tuning I feel this little 4.3 that could will be a beast in my 20' cuddy.

Also, my solution for the raw water pickup worked perfectly fine. For fear of the impeller having some kind of sealing purpose, instead of removing the impeller from the alpha drive I cut all of the blades off of it. I used vacuum rated hose from the transom to the pump and also installed an Indmar sea strainer so I could see the water flow. With the closed loop system beating on it as hard as the fuel would let me, I saw 160-180* temps the whole outing.

So far so good... oh and no signs of water reversion either. Idle was around 850 RPM.
 

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kpforce1

Cadet
Joined
May 5, 2017
Messages
22
Got a chance to actually beat on the motor tonight i need to back timing down from merc spec by 2 or 3 degrees as i still had ping above 3/4 throttle. I found a 21P Highfive prop new for $150 to try on it. All I can say is man, this thing RIPS! My engine, exhaust and the H5 were flat out beastly. I could cruise at 45, drop the hammer and it would push you in the seat to 50+. With the 1.8 outdrive and this motor, the H5 21p is not enough prop lol. It would have climbed well past 6k RPM if I let it. It would blow out if I hammered it below 25mph.

it took 2 seconds or less to get on plane. It got great mpg cruising and would suck gas like a 350 if I opened all 4 barrels. Impressive. If anyone wants more than 350 power and v6 fuel consumption this is the ticket.
 
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