Rapid Runner repower/refit

[Hondaz]

With not much going on the web board. I thought I should contribute my little project. I bought a 4.6m Rapid Runner running a raw water cooled 302W and 773 last year and ran it as is while collecting the parts and looking for the time for the rebuild. Enter lockdown... Actually I had removed the motor and sold it prior but that's about it. I'm also using this as a learn to TIG project so be gentle as there is some ugly welds on there.

[Hondaz]

Turns out you shouldn't judge a book by its cover... The boat turned out to be pretty badly put together. When I turned up for the test drive the boat was tied up at the ramp ready to go. The first time I tried backing it off the trailer when I got it home I needed to get so far in the river as to have the drawbar on the trailer totally submerged! Back on the trailer I found not 1 but 2 wedges fitted to the unit. On the test drive I had noticed it was pretty nose down. The 2 wedges meant the reverse bucket wasn't engaging fully. Rang the last owner who told me he just got in the water deeper to get it off the trailer. Turns out all the gear got swapped out of an old steel hull with fuel tanks in the back and it looks like nothing got changed. Removed the wedges. Fixed reverse - much better.

The front seats were mounted on some butt ugly and poorly designed pedestals that were just screwed to the ply floor! I found this out the second time I had the boat out and ripped the seat base right out of the floor doing high speed Hamilton turns... Note to self. First thing to do on refit and be gentle till then. Drilled more holes in the seat base and found some better screws till then.

[Hondaz]

Into the project. Pulled up the floor and found this abortion. Some packers used to lift the floor level to clear the fuel tank. That's why the seats were only into the ply.

[Hondaz]

Marinising this. Decided to go for Hi-Flow manifolds and run the standard car ECU after trawling this forum over and over again. Also going for HX rather than raw water. Also fitted a unit protection plate/ride plate before a 3 week south island trip earlier this year on the old motor. Will also be fitting dual upgraded bilge pumps to replace the single 500GPH unit.

[Hondaz]

So I'm also trying to get more rear seat space as I previously only had about 5 inches between front and rear seats. The motor is an L98. I've flipped the intake manifold 180 degrees to gain some space.  I had to machine off the oil pressure sensor boss on the valley plate and TIG up the cast Ali hole... First TIG job. While I haven't run it yet it looks like it's sealed up alright. I bought a adapter off EBAY to replace the oil bypass cap on the side of the block to fit the factory oil pressure sensor and also to take the gauge sensor. Some minor clearancing of the inlet manifold plastic honeycomb was required around the PCV outlet. Other than that it seemed pretty straight forward (so far).

[Hondaz]

I'm going to keep the PCV system operating but have added a little catch can/filter unit from Ali Express into the line to try and reduce the amount of oil mist going in the intake manifold. Mounted up the front of motor where the power steering reservoir was. Header tank fabricated and put on the opposite side and steam tubes plumbed in. Heater bypass hose from Ali Express. Yeah... I don't want to spend money on it if I don't have to. I've gone for an easy/cheap serpentine belt routing. Removed the PS pump and replaced the lower fixed smooth idler with a grooved one and countersunk an alternator mounting bolt. Easy and cheap.

[Hondaz]

Bought a new H bar as the original driveshaft setup on the 302 was long and ugly. First trial fit in the hull showed I had sump clearance issues at the rear of the sump around the intake of the jet unit. Was thinking about options for cutting and welding when luckily one popped up on trademe that had been done already (and had extra volume added to the front) and came with a pickup and dipstick. All for a couple hundred bucks less than I sold my standard one for! When I went to change the sump over however that couple of hundred dollars disappeared real fast... There was a piece of shiny metal in the sump. I had seen a vid of this motor running but started to get pretty nervous. Turned out to just be the cam chain tensioner slipper and is apparently a weak point on these motors. Replaced it with a LS2 style dampener which is supposed to be stronger. While in there I also replaced timing chain, oil pump, and water pump. I was going to leave that stuff alone as the motor supposedly had 160km on it, but now it's done and I don't have to worry about it again. While I was playing with the motor I did the rocker cover gaskets as well as these had shown signs of leaking. The oil pickup that came with the sump, while modified wasn't a straight bolt in fit but a bit of careful measuring, minor tweaking and a new support made up and it's probably as good as the original. Also the dipstick that came with the sump fitted through the block and not the sump like the L98 but there was a knock out plug in the block that came out easily enough and I re-marked the dipstick full level after careful measuring of the old, new and windage tray etc. Minor tweaks to the dipstick tube put it in a suitable out of the way place. I also ditched the oil level sensor that was in the original sump.

[Hondaz]

Fabricated up some new alloy engine mounts to suit adjustable feet. Tacked these together while I practiced TIG a bit more on the new front seat bases. The seat bases fit a couple of plastic ammo boxes and are skinned in thin alloy and will be carpeted to hide dodgey welds. Photo shows old pedestal on passenger seat. New seat bases spread the weight better and can be bolted to bearers and are lighter than old steel pedestals.

[Hondaz]

Got brave enough with the TIG one day to glue the engine mounts up. Those who are wondering about the front mount up right bits - they are recovered bits from an old telecommunications rack hence the 6mm tapped holes. May come in useful layer for mounting stuff. Lots of that sort of thing on this project. I'm planning on putting a ring gear splash guard in at some point in the future.

[Hondaz]

Threw the motor into the boat and aligned the driveshaft. Had minor panic attack when I realised I had set up the mounts for the motor to be parallel but it turns out I had way too much vertical offset and the driveshaft angle was too high - yoke nearly touching the H. Went for a broken back setup in the end after using the Hardy-Spicer online calculator for driveshaft alignment angles. Couldn't measure angles to that degree of accuracy but can measure distances and can do trig ok so hopefully it works out. May have to end up pulling it all out again anyway and machining a few mm off the driveshaft as I only have 2mm of spline joint left.

[Hondaz]

Fabricated a couple of exhausts out some old 80mm alloy 2mm wall tube I had laying around (recovered LARGE coaxial cable outer). It's a bit bigger than 3 inches but I can just squeeze it into the silicone couplers. I'm not sure how long the tapes going to hold though.

[Hondaz]

The header tank is made out of the same alloy tubing. Also slipped the fuel tank back as far as possible to gain enough space to get the floor down flat on the bearers. Trying to shift weight forwards now to offset that. Moving battery to front by throttle pedal and sunk into floor up there so I have easy access to isolating switch (not previously fitted on boat  )

[Hondaz]

Again re using scraps of ali laying and and cutting down the old battery box to line it. It also stops passengers from kicking the throttle. Also moved the throttle to a better position - was almost in the centre of the boat previously!

[Hondaz]

While we are talking throttle... Made a pedal box to house car throttle pedal driven from Morse throttle. Mounted up on the transom above the left exhaust

[Hondaz]

One of my bargain buys was a complete 20/40 underfloor heat exchanger and header tank. The header tank didn't suit at all but the HX will hopefully be enough to cool the LS (was on a 351) and just fits in the hull nicely and the engine side just comes up inside the engine box nicely. Had to chop out a bearer stiffener to get it in there but have bolted a new one in there so I can access it if I need to. Also the front plumbing connections are right under the new front seat base so I'll cut an inspection hatch in the floor under the seat to access these.

I've also removed a ton of excess crap off the sandtrap and plumbed the dump through a new skin fitting as it used to dump inside the hull. See picture for removed parts. I'm also trying to keep the water flowing nice and fast through the HX.