Rapid Runner repower/refit

[Ross Goldsack - JBNZ Immediate Past President]

Great to see someone getting stuck into a project. Often it's only when you start ripping it apart you find all the boats secrets  nothing that time, ingenuity and $$$$ can't fix.
This web board is dieing and without fresh projects like this. Thanks for posting 

[johnmead]

great job going on there  Are you going to support or fasten the HX in any way to stop it jiggling/wiggling and wear a hole in itself?

[Hondaz]

Yeah half done already John but no pics. Just a couple of padded pipe clamps on each tube.

[Jeff B]

Sounds like it was put together a bit boogie to start with....
Nothing time and $ and more time won't fix.
Putting the battery up front like you have done is not common, what route will you take with wiring?

[Hondaz]

I think I can possibly squeeze it down next to the fuel tank. If not then it can go under the tank in a piece of conduit. Or perhaps a combination of both. Maybe just the main power connections heading towards the motor and run a bus system at the engine for simplicity? Not entirely certain yet on the details. I'm an electronics tech by trade so I'm pretty sure I can figure that part out.

[Jimmy Jet]

 Cool project, looking good. All I can suggest with the tig and welding anything that holds liquid or pressure is to test it up. Can be quite deceiving how good a weld can look (esp to the lesser experienced) and yet it can weep. Welds are looking pretty decent considering.

[Hondaz]

Thanks Jimmy. Yeah I pressure tested the header tank as it stands at the moment and no leaks after half an hour so figured it was good enough. Will do the whole cooling system once I have it together. The exhausts will be a suck it see though unfortunately. Hopefully doesn't fill the boat with water... Going to fabricate a surge tank last so that's the one I'm a little concerned about. Will definitely pressure test that one. The surge tank will be xx oversized to get a wee bit more fuel into the boat and also to try and help keep the fuel cool feeding the motor.

[Hondaz]

HX and fuel tank mounted. Began plumbing HX.

[Allen M]

Looking pretty good so far Lots of pictures are even better.
Battery box idea is great but I hope you?ve left a bit of space between the bottom of the battery and the hull. This area of the hull can take some pretty big hits and it wouldn?t be good if the hull flexed up and smacked the bottom of the battery.
Great thread,keep it coming 

[tyro]

I remember when building my boat I was told have the battery as close as practical to the motor as possible and I remember reading somewhere in the depths of this forum (can't find the post) that long leads to the battery was a bad idea? This is just stuff I was read/told so there may not be anything truthful in practice in it -just throwing it out there would be interesting to know

Also would the battery get more shock at that position from wave joggle etc versus rear of boat, probably not an issue if using a nice battery like an optima?

[Hondaz]

HX engine side plumbing done and tested. Once I sealed the thermostat housing it was pretty good. One minor pinhole found and repaired at 18psi. A couple of leaky hose clamps. I think there is about 3 different alloy antenna booms in that plumbing arrangement.

Re the battery thing. Yes there is a bit of space between the battery and the hull. The battery also sits in a plastic sealed tray up to floor level in case of acid spills. The whole arrangement is suspended from the floor (with a tight fit) as opposed to mounted on the hull. I was just going to strap the battery into the box. It's about 3M of cabling required to get to the starter motor and if we estimate say 350CCA (worse case? Someone could measure) I think the volt drop is probably fine with 25mm cable. 16mm might be a bit light. 35mm would also be fine but getting heavier physically which I am trying hard to avoid. Worse case scenario I have some 70mm cable here but will move the battery back before going to that extent. I could also consider a gear reduction starter and just call it a maintenance item to increase reliability to get it past the bank manager.

I'm pretty sure Dad's old Jet52 had the battery in the floor - maybe between the back to back seats? I don't know, it was a long time ago. Plus with it like this it can't be any worse than when I got the boat... It was in a staple type box in the back corner and not tied into the box in any way

[johnmead]

HX looks good 

[Jimmy Jet]

I'd err on the side of caution with the cable. Go heavier if you can, 50mm maybe.
Look at worst case scenario for the CCA and add in more leeway.

[Warwick Marflitt]

Copper and alloy joined together in boats can cause Galvanic corrosion. Don't let it eat your boat? Copper is more noble than aluminum....   

https://www.google.com/search?client=firefox-b-d&gbv=1&q=copper+and+aluminium+in+a+boat+galvanic+corrosion&spell=1&sa=X&ved=2ahUKEwj80viVjNjyAhVBzjgGHZqdCO4QvwV6BAgMEAE

[Jimmy Jet]

What would you suggest Warwick? Sacrificial pencil anodes in the cooling system? That type of cooling arrangement has been around for a long time now in jetboats, is there actually much evidence of either hulls or aluminium engine components sizzling away at a huge rate in jetboats with that type of cooling arrangement? Can any others comment?