at last .

[roofer]

my new boat is ready at last , gonna pick it up from hutchy's tomorrow and take it for a blast . need to get loads of practice in cos first race is in a couple of weeks.

anyone know how long it usually takes for a race licence to arrive?

 

[K9 racing]

i think its about a month but you can pay a extra 100 quid for it to get to you faster!!

 

[roofer]

done 2 days testing on new boat and apart from a fuel problem im well impressed. this boat is seriously quick and a real handfull .had it up to 7500 rpm today and was really flying,cant wait for calmer weather .

 

[Taz]

Hows your engine roofer you got any pics of your set up? I just mounted my one today

 

[Taz]

What speed you had out of it? Is it loud?

 

[roofer]

taz engine is superb, the sound it makes is awesome and performance is staggering. i need to have fuel pickup altered and then i reckon it'll do around a ton .im using a chopper 141/4 x 25 and it just keeps on accelerating ,im going to try a 27 yam prop on monday. i'll take some pics next week of setup.

 

[roofer]

i was probably running in the 80's ,heres a pic a bit crap but look at the rooster.

 

[Captain Chaos]

bring'm on roofer. the more the merrier

 

[Taz]

How do you mean fuel pick up altered? It not getting enougth fuel?

 

[roofer]

the fuel pickup in my tank is meant to fit in a depression at the bottom but it looks like it doesn't, hutchy fit a swirl pot to keep the injection system pressurized but when tank gets low its drawing air so it looks like pickup is not on bottom of tank .

 

[Taz]

Oh right got ya bummer i fought you had a new tank? my pipe just comes out the bottom of the tank. ive got the problem with the return line as ive only got two holes in the tank and ones always been a breather so im not sure if i can use that as a return and maybe t piece it or leave the filler cap a little loose to let the air in.

 

[JamesM]

Taz if you have the mercury fuel filter water separator jobby the one that takes the screw on filters (like a car oil filter) you can run your return line back to that. If you look at it it has two inputs and two outputs identified by arrows in the casting. You just need an extra fitting to replace the blank in the spare input.

This method does work aslong as the filter is before the pump, but its generally thought of as second best.

 

[Jon Fuller]

Only trouble with that method, is that any air bubbles present in the fuel, get re-circulated back into the system rather than gettin rid as you do when it's returned to the tank.

 

[Taz]

Yes i do have the mercury seperator good idea. why should there be any air bubbles in the fuel? If its a pressurised system and the fuel intake is at the bottom of the tank and you keep your fuel topped up how can air get in jonny?

 

[Jon Fuller]

When you're tearing along at 75mph, bouncing all over the place, on your side, nose up, nose down, etc, the fuel in the tank is sploshing about all over the place like a fkkn washing machine!, it's very easy to draw some aireated fuel from this scenario, especially if you're low-ish on fuel.

A fuel tank with a sump helps.

In our race boat, we had a separate reservior/fuel-air separator, with internal baffles, and a high volume pump filling this from the main fuel tank, and a return from the top of the reservior, back to the tank.

This reserviour was tall (18") and quite narrow (body was 4" dia tube) the main high pressure fuel injection pump, then drew it's supply from the bottom of the reservior, ensuring a stable airless supply at all time. The return from the fuel pressure regulator at the fuel rail, returned to the reservior/air separator.

Before this system was installed, toward the end of a race, the motor would start to run real shitty as the Mercruiser system for coping with aireated fuel became inadequate.

To make re-engining easy, (as some boats don't have easy acces to the fuel tanks, so fitting a return line could be hard), Mercruiser fitted a system with a float & valve in a chamber to remove any air that came from the tank, this meant a return fuel line wasn't nessasary, this system was probably fine in a cruiser, or pleasure sports boat, but when your running flat out for an hour and a half, and need to be able to use all the fuel in the tanks, it was useless.

Another big issue with high power fuel injection, is making sure the bore of the fuel supply line is big enough, very often, the fitting used for things like filter heads, bulhead fittings and tank dip tubes etc, have a considerably smaller bore than the hose that they supposed to be used with, this results you thinking your 3/8" bore pipe is sufficient, and can't be the reason you have fuel starvation, but one of the fittings could have as little as 3/16" bore inside!, I've seen this many times, and I always rig such a system with 1/2" bore tube through-out, and check all fittings for 'free flow', and re-drill larger if needs be.

Run a fuel pressure gauge directly from the fuel rail to ensure you have adequate pressure "at the injectors".


All Just IMHO

 

[roofer]

jon i have the system you have described fitted in my boat and it still draws air when the fuel is getting low.i have a long thin plastic tank fitted with a sump, we are going to check tomorrow that the fuel pickup pipe is on the bottom and not stuck up in the air .

 

[Jon Fuller]

If your hi-flow primary pump and header/separator tank are set up correctly, and of the right design, I can't see how it wouldn't be able to supply fuel 'uninterupted' to your motor!

Unless the main fuel tank is completely unsuitable, which I doubt, coz Hutchy would have spotted that at the outset.

OH well, you'll get there in the end.

 

[roofer]

jon we think the pickup pipe in the fuel tank is loose or has moved,boat runs fine untill fuel is below 1/4 of a tank .

 

[Jon Fuller]

Ah right!

 

[roofer]

turns out pickup pipe was sticking 2 inches off the bottom of fuel tank,runs perfect now.here's a few pics of boat now its finished apart from graphics.