Outboard to inboard swap?

[fishbum]

Hi guys, after breaking 2 jet intakes in the last 2 weeks I am thinking on a swap to inboard. I have a almost new hull that is 1866 27" sides, 190 bottom and .125 sides, has a high transom but that can be changed. It has a flat front but has a slight V bent into the hull maybe 3deg at rear. anyway looking for Ideas and comments. at this time it has a tunnel and 5 2" stringers in the hull. Thanks

 

[PSG-1]

It's definitely do-able. Looks like a great boat to do it with, too, metal is new and clean, it would be no problem to weld it.

Take a look at my Aluma-Jet for some pictures and detailed information on exactly what is involved in modifying a boat for an inboard jet.

 

[Kevin Turner]

I'm guessing you've considered a poly intake?

As far as OB-IB swap; Yes, can be done...but with all you've gone thru so far (with this hull) I think you'd be $$ and stress ahead if you sold your current rig...and purchased a IB.

 

[fishbum]

I'm guessing you've considered a poly intake?

As far as OB-IB swap; Yes, can be done...but with all you've gone thru so far (with this hull) I think you'd be $$ and stress ahead if you sold your current rig...and purchased a IB.

Kevin, I know I know, we have talked some for a few years, I like the open room on a outboard boat. have been in a couple ib boats in the last couple months and the power is nice. Think you know my friends (Trent)and Jammie T. from Ga.
of course money is also different not so much if you buy everything new but I almost never do.

 

[fishbum]

It's definitely do-able. Looks like a great boat to do it with, too, metal is new and clean, it would be no problem to weld it.

Take a look at my Aluma-Jet for some pictures and detailed information on exactly what is involved in modifying a boat for an inboard jet.

Have looked at your build, Think this boat is to heavy for the ski stuff? I also carry a 50 gal bait tank all the time.
I know there are some bad ski motors now but how about there pumps? I have just seen some used 175, 210 sport jets for sale in fiberglass boats for 3-5000 Just had a brain fart I guess.

 

[PSG-1]

Kevin, I know I know, we have talked some for a few years, I like the open room on a outboard boat.

Inboard jets can be designed for room, too. If the cowling and rear deck are built properly, it takes up no more room than the rear casting deck of many open-type johnboats, like my Triton 1650.

Admittedly, room is tight on my boat, but it's a center console, and that eats up a lot of room being able to move around. It works for me, as I rarely leave the helm, except to get out of the boat, or to set the anchor, and if anybody is riding or fishing with me, they have the area forward of the helm, and the elevated front deck for fishing/casting.

 

[Kevin Turner]

IMO-
Best performance for the buck and ease of install... A 175 SJ from a donor 'glass play boat. Compact, light, and no external exhaust to deal with. That'd give you most all you need except the SJ pump aluminum jet tunnel. Night Construction outta the Snake River Valley sells the tunnel, ready to weld in for $500 (+/-). With such a shallow deadrise, the raised tunnel will help the hull turn.

 

[semojetman]

I am building an inboard boat also.
If you wish to know anything that i have already researched, i will help you in any way i can.

Mine is a 1856 Blazer SS with a drop down 8 foot ride plate in the center of the hull, a 6.0L Vortec V8, Berkeley 12JE, dual consoles, bench seat, low profile engine hood/casting deck, swim platform on back.

 

[PSG-1]

It's definitely do-able. Looks like a great boat to do it with, too, metal is new and clean, it would be no problem to weld it.

Take a look at my Aluma-Jet for some pictures and detailed information on exactly what is involved in modifying a boat for an inboard jet.

Have looked at your build, Think this boat is to heavy for the ski stuff? I also carry a 50 gal bait tank all the time.
I know there are some bad ski motors now but how about there pumps? I have just seen some used 175, 210 sport jets for sale in fiberglass boats for 3-5000 Just had a brain fart I guess.

My boat carries 22 gallons of fuel, and weighs about 1225 lbs when loaded with fuel and the battery. I'm running about 170 HP with the MR-1, and it pushes along pretty good, even with myself and 2 passengers, which is another 500 lbs.

If your boat is in that weight range, you would be OK, although, that 50 gallon bait tank adds another 500 lbs by itself, without passengers or gear.

in that case, something like a 1494 cc Sea Doo Intercooled Supercharged with 215 HP would be a good candidate, as would the massive 1800 cc Yamaha 4 stroke.

 

[Kevin Turner]

My boat carries 22 gallons of fuel, and weighs about 1225 lbs when loaded with fuel and the battery. I'm running about 170 HP with the MR-1, and it pushes along pretty good, even with myself and 2 passengers, which is another 500 lbs. If your boat is in that weight range, you would be OK, although, that 50 gallon bait tank adds another 500 lbs by itself, without passengers or gear. in that case, something like a 1494 cc Sea Doo Intercooled Supercharged with 215 HP would be a good candidate, as would the massive 1800 cc Yamaha 4 stroke.

With respect, I've been down this road. The limiting factor is the pump. None of the above pumps can provide the static thrust needed to plane Fishbum's craft as well as the SJ pump.

 

[PSG-1]

Not sure what the specs ore on the SJ pumps.

But as far as my boat, I'm using the pump from a 1998 Yamaha XL1200W, it's a 155 mm pump, and I'm running a 13/19 pitch Concord (swirl) impeller. And even with the weight of my boat, it has NO problem with hole-shot, very impressive acceleration.

 

[Kevin Turner]

Not sure what the specs ore on the SJ pumps. But as far as my boat, I'm using the pump from a 1998 Yamaha XL1200W, it's a 155 mm pump, and I'm running a 13/19 pitch Concord (swirl) impeller. And even with the weight of my boat, it has NO problem with hole-shot, very impressive acceleration.

So often I hesitate to post, for fear of coming across as "combative". I assure all that is not my intent.

Again, with respect...Comparing your craft to Fishbum's is apples to oranges. I've tested the MR1/155 in a heavily loaded hull and it doesn't perform near as well as the 175 Sport Jet. If time permits, I'll start another thread comparing various 'ski engine/pump combos I've built and tested.

 

[PSG-1]

I guess the shape and construction of the hulls, or the weight of these boats compared to mine, must be different.

Hard to believe the MR-1 wouldn't be powerful enough, but if you've actually done testing with these, then, I'm not going to argue with facts.

I haven't done any testing, only built one jetboat, in fact, and simply did a motor upgrade from 2 stroke to 4 stroke. And I guess I just got lucky and had a good combination of everything that works, especially considering I had no blueprints, etc.

But I'd definitely be interested to read through some of those test results when you post them, it's good information to know, in the event I start building any boats, I'll know what works and what doesn't.

 

[Kevin Turner]

PSG-
I have a ton of respect what you've done. And it's clear it works very well in your hull. Also, the 155 will "work" in heavier crafts, but not as well as the SJ. Here's some "general", quickly typed points. Time is short and I'm not the fastest on the keyboard.

Water is retentive, so when working with a sled nosed craft (Fishbum's) water grabs and holds on to the abrupt entry angle. Fisrt, we hafta lift the nose to shear the water's grip. Not difficult until you factor in the operator's weight near the nose (where we need to lift) and the mid ship bait tank.

The key is thrust created at rest or slow forward motion. The small 155 intake & impeller spools quickly, but the hull is moving slowly. Unlike an OB jet pump, which stays loaded b/c you can trim the intake deeper into the water, the IB intake relies on the "ram" effect b/c the impeller is higher in the hull.

Look at the long intake ramp of your 155. Great for loading at higher speeds, not so at slow speeds. The 155 struggles to plane heavy loads. That's why the big 'glass play boats use twins.

Now, the XR2 175 uses a 7.25" impeller (155-6.1") that is underdriven to get slower blade speed. The slower, but larger blade flows more water. The short, steeper angle of the SJ intake ramp allows the pump to reload quicker at rest. At rest, the SJ flows more water, stays loaded longer, thus more static thrust. Heavy or "wet" crafts need lotsa low "umph" to plane quickly.

 

[fishbum]

Good stuff Kevin, I know you we're looking at different motors when it looked like sj were going away,
Did you ever find what you would do?
As far as this issue what is the difference in the 210 motors in the later boats ?
I think exhaust is one? Is that hard to deal with?
You bought that 210 pump housing from Jamie right?

 

[fishbum]

Just thought about something else,
Guess I would have to mod the transom as it has a angle built for outboard!
Maybe just build out kind of box to bolt up pump?

 

[PSG-1]

PSG-
I have a ton of respect what you've done. And it's clear it works very well in your hull. Also, the 155 will "work" in heavier crafts, but not as well as the SJ. Here's some "general", quickly typed points. Time is short and I'm not the fastest on the keyboard.

Water is retentive, so when working with a sled nosed craft (Fishbum's) water grabs and holds on to the abrupt entry angle. Fisrt, we hafta lift the nose to shear the water's grip. Not difficult until you factor in the operator's weight near the nose (where we need to lift) and the mid ship bait tank.

The key is thrust created at rest or slow forward motion. The small 155 intake & impeller spools quickly, but the hull is moving slowly. Unlike an OB jet pump, which stays loaded b/c you can trim the intake deeper into the water, the IB intake relies on the "ram" effect b/c the impeller is higher in the hull.

Look at the long intake ramp of your 155. Great for loading at higher speeds, not so at slow speeds. The 155 struggles to plane heavy loads. That's why the big 'glass play boats use twins.

Now, the XR2 175 uses a 7.25" impeller (155-6.1") that is underdriven to get slower blade speed. The slower, but larger blade flows more water. The short, steeper angle of the SJ intake ramp allows the pump to reload quicker at rest. At rest, the SJ flows more water, stays loaded longer, thus more static thrust. Heavy or "wet" crafts need lotsa low "umph" to plane quickly.

That makes a lot of sense. You're exactly right about how the 155 mm pump winds up quick, but doesn't have much low end thrust, at least, not until you really hit the throttle, then it will pick up and go. With the flat bottom, when idling, that long intake ramp tends to shuttle a lot of air into the pump at low speeds, which causes a certain degree of cavitation, even at a fast idle.

Did some reading on your website, good info. I can see from the line drawing that the SJ pump has more angle in the back end, it's not a flat pump like the Yamaha XL1200, so, I can see how that would help to have better hook-up in the chop, as well as proper loading at lower speeds.

I'd love to have a pump that can perform better in chop, as the Yamaha 155mm pump isn't exactly the most efficient pump in terms of moving water, and if I have my boat in some chop, it has a tendency to catch air in the pump, I have to keep the throttle at about mid-range, around 6200 RPM (redline on my boat is 10K) I hate cavitation, because it puts a lot of undue stress and vibration on components. My boat and I must be telepathically linked, because it hurts ME when the boat cavitates. :shock:


With that said, when I build my next jet, I don't think I'll use a Yamaha XL1200 pump, I want a better option. Was thinking of using the Aqua Jet pump, because the impeller is so massive, especially compared to a conventional PWC impeller, even I would have a hard time of wearing it out!! But the AJ is about 3500 dollars. I'm curious how much the SJ pump costs, and how it compares to the AJ.


So, my questions are, what does the SJ's impeller look like? How thick is the housing itself? Can they ingest the occasional stone or rock without sustaining damage?

The worst I usually run through is oyster shells, but in the event I did want to go above the fall line of a river, and into some rocks, I definitely don't want to do it with the 1/16" thick casting of the XL1200, I want something a little more stout.

Also, what's the average minimum HP required to effectively run the SJ pump? Could it be done with the 160 HP MR-1 engine, or would I need something with more torque and HP, like the 215 HP Sea Doo Intercooled Supercharged engine?

Thanks in advance!

 

[PSG-1]

Just thought about something else,
Guess I would have to mod the transom as it has a angle built for outboard!
Maybe just build out kind of box to bolt up pump?

I didn't modify my transom angle, it's the same as it came from the factory. I simply had to fabricate my tunnel so that the pump bolted in flush. But then again, my pump is bolting up from the underside of the boat, not from the stern. Guess it would depend on the type of pump used.

 

[fishbum]

thanks for the input guy's, Just have to think about if spending the money for this is worth it, Kevin, can you tell me how much deck from the tramsom to the front of the motor it would have to have to clear? Thanks

 

[Kevin Turner]

Kevin, can you tell me how much deck from the tramsom to the front of the motor it would have to have to clear? Thanks

As luck would have it, here's pics of 1866 OB Jet I converted to a 175 SJ.