1974 Mako 22B

I have a 1974 Mako 22B that I want to convert to a jet drive boat. These 22B hulls are moderate V hulls which are almost flat on the bottom at the stern and perfect for a jet drive in my opinion. I use my other Mako 22B weekly to fish with but the ride is less than spectacular in choppy seas due to the moderate V hull and I'm sick of throwing money at outboards. I have a very nice Berkley 12JC complete on hand and was wondering how much room would a typical setup using a Mercruiser 5.7 (which I also have laying around) would take up? Distance from the transom to the front of the motor? Should I use a Mercruiser 4.3 V-6 instead? I have cut the factory storage compartments out and that has left me with 40" from the transom to the deck where I cut the compartments out. I can take much more deck if needed but I really want to get the motor and drive as far back towards the transom as possible. I plan on closing in the transom and understand that obviously the center stringer will have to be modified and the jet intake cut in thru the bottom as well as cut out in the transom for the pump which is no problem. I've spent every summer of my youth working at Peninsula Marine boat yard in Stock Island, Fl and I am well versed in fiberglass boat construction,repair and fabrication. What I need is ideas on how to accomplish the install using as little space as possible inside the hull. I seem to recall setback installations in boats that I've seen from time to time but not sure how to achieve this without some input. Thanks in advance!

 

Have you seen any other of these boats with jet installations ? I would be concerned about the suitability of the hull shape for a jet, I'm not saying it is unsuitable in this case, but if there is a tendency to broach, at all, it will only worsen with the jet. Most jet boats have cutaway forefoot shape, deep footed boats give problems especially in a shallow vee design, and this one is a shallow vee, but what is the underbody forward ?

 

Mako offered the 23 ft model with an I/O setup but not a jet pump model that I'm aware of unfortunately. The only difference in the 1974 22b and the 1974 23 with an I/O is 1'3" in overall length. The beam,transom height,draft were identical. The 23 weighed more by 750 pounds. I'm not trying to turn it into a speed boat by any means I was just wanting to utilize these parts I have and hopefully end up with a dependable fishing boat. The under body forward from the cut out area is where the fuel tank is located. There is 27" from the edge of the cut area to the leading edge of the fuel tank which extends into the center of the boat (51 gallons) and on the 23 straight inboard model this is where the engine would be in the middle of the hull.

 

As I say, it is the possibility of broaching being amplified by jet drive that would concern me. It might turn into a hand-full. And it should be noted that fuel use will rise noticeably compared to a sterndrive, jets would be less efficient at your likely cruise speeds.

 

Broaching concerns are noted and I appreciate you pointing out this scenario as a possibility. I've personally never even come close to broaching this hull so I would say that there is no tendency for these hulls to broach nor have I ever heard of a Mako broaching. I was hoping to find out what kind of room would be necessary to accommodate the jet and power plant. Distance from the transom to the front of the motor? V-6 4.3 liter with Berkley 12JC? V-8 5.7 liter with a Berkley 12JC? Set back install information? Would a stern drive be a better option? Help with these issues would be greatly appreciated as well. Thanks.

 

There were some smaller Mako centre consoles (19, 20 Feet ?) seen in this part of the world back in those days, and it reached my ears that they did have broaching tendencies. Is there some kind of external keel or skeg on your boat to keep it tracking straight ? Hard to see how such a shallow vee would stay on track without one.

 

No external keel or skeg on the hull and honestly the boat doesn't track well even with an outboard motor! Would a stern drive be a better fit?

 

I do not see why it would not work. I would probably add some large running strakes to the bottom (by large I mean 2" or more profile). You can also put some small fins on the jet nossle. I used a couple of these fins on my runabout and it made a world of difference in both slow and high speed turning

http://www.cobrajetsteering.com/index.php

 

Nice boat! By running strakes are you referring to the structures half way up your hull wrapping around the stern? My Berkley 12JC has a rudder on the nozzle but its a single rudder not the dual system like the cobra jet. Most boats I see running jet drives are extremely flat bottom hulls how do they over come the tracking and broach issues?

 

Maybe 20 or 30 years ago you could get away with claiming that jets are less efficient than stern drive, but not today. They are much more efficient now, and at speed above 25 knots, they are more efficient than props of any kind, no drag factor. Mr. Efficiency.

 

Funny then, that the recreational boating sector hasn't caught on to this leap in jet efficiency, that I can see. Is the jet unit brand/model an example of the new breed of jet unit you speak of ? And I would think 25 knots would be beyond this boats comfort zone in "average" offshore conditions, anyway. But, the main issue is, is this hull suitable to run a jet ? I don't think so. So, while it may well be that some quantum leap has occurred in the efficiency of jet drives (I'd like to learn more), it really isn't likely to be applicable here.

 

I'd say they overcome that by not having any depth to the forefoot area.

 

Google Berkeley 12Ja Install- boat design and you should get an earlier thread that has some dimensions for different engines with measurements
Note that they are using a different pump than what you have, it looks like a 12JG which had a flange to mount the pump to the transom very much further back than the 12jc

With only 40 inches from the existing front bulkhead to the fuel tank, you will need to push out the transom to accommodate the length of the pump/engine combination but note that you will have to deal with leaving enough access to the hand hole clean out plate on the top of the pump
Not sure if you can make the 40 inches work.

Just some random neuron firings, ( as it has been quite a few years since we used them)

1) you say a complete kit, if you have the transom flange you have to ensure that it came off a boat with about the same transom angle as there were two of these flanges to accommodate different transom angles within certain ranges. Google the ranges

2) You will need an intake adapter that mounts to the bottom of the boat to which the pump actually mounts to

3) There are two ways to hook up the motor to the pump, one is to mount the pump, then mount the motor on say a 4 point mounting system, install a flywheel adapter that allows you to bolt up a short u joint shaft to the pump. This is the hardest method and makes the whole pump/engine assembly longer. Concentric alignment of the engine and pump is one issue

Berkeley had a flywheel housing that had a cone that bolted around the collar on the 12JC pump that centered the engine to the pump. Then they bolted a flywheel adapter onto the flywheel, and their proprietary short u joint bolted to this and the spline just slid into the pump. This is the easiest way
There is a chance that a Mercruiser has a flywheel housing of the same dimensions as the Packajet and you might be able to just buy the cone adapter

Seems to me that they did not use a flywheel but rather a balanced ring gear that was toothed for the starter. I expect that this was to reduce weight and perhaps cost


4) With this length of boat, you should go with at least a 5.7 engine for good performance. You can easily find the Berkeley horsepower to impeller curves to pick an engine and match the impeller to the engine off the net.

If you have a modern 5.7 engine, higher horsepower, look at the charts you might consider the AAA impellor as these gave us the best performance. Originally we used 460 Ford or 454 Packajets putting out about 300-330 hp prox. but used some newer EFI
5.7 with the same impeller. The triple A impeller dropped the engine rpm considerable and helped with fuel consumption

It is difficult to offer input about your hull would be susceptible to broaching as some contributors have mentioned but this is a real concern. We built mainly 12 degree monohedron and some 18 degree monos as well. A deep forefoot might be an issue.

Your comment " I have never come close to broaching this hull" does not cross the boundary between either an IO/OB and a jet, as the leg portion of the first will keep the back from swapping ends in a tight high speed turn. The other contributors have pointed out an extremely valid trait of jets with respect to hull shapes and tight turns.

American Turbine makes a mixed flow pump and would probably have parts to make your pump work and I think another company took over manufacturing replacement parts to service Berkeley pumps as well. CP something?

 

Thank You, Thank You, Thank You! You have more than addressed everyone of my initial concerns with fitting the drive and then some. Excellent information! Thanks again.

 

Just a couple of other points
Berkeley /American Turbine jets are very prone to losing thrust with either small rocks lodged into the intake grate or very small pieces of wood that can get through the grate into the inlet side of the impeller. The pump can then cavitate and you lose thrust.

If you back up with these pumps in shallow small rocky water, often the small rocks will
wedge the reverse bucket so you cannot get it to move to a forward position.

Weeds are not often processed very well through either the intake grate or the impellor
( ski ropes even worse)

You can build a small rake that has a 90 degree bend in it to clear the intake of weeds and jambed rocks.

If you are going to be fishing in very weedy areas the jet might not be the best choice

If you get weeds or a small stick into the inlet side of the impeller, you have to remove the hand inspection plate and stick your hand into the bowl to remove the junk.

Obviously the inspection plate has to be above the height of the water or you have just opened a 4 inch hole into your bilge. You can get an inspection port extension but then it is even harder to reach through this to get into the inlet side of the impeller and this becomes difficult if there is not a direct vertical access to the access port