Recent content by speedboats

Carbon seal and spring would've been bouncing around on the mainshaft in front of the impeller. This could have created a 'rumbling' sound as the impeller tries to cavitate. It is likely that the bearing is knackered, the emulsified oil and water isn't the greatest at lubricating. I'd bet a...

The jets are un-complicated and have few moving parts. You are unlikely to need to replace the impeller as was implied a few posts ago as the grill will stop crap getting to it. You have 1 thrust bearing at the front (QJ308 in a 212, brass cage, split inner) and a rear bearing (cutlass in a 212...

Yes the bottle is a sealed vessel. The same too could be said if the intake and nozzle freeze first, then what is left inside the pump is essentially in a sealed vessel. This is feasable as the section inside the hull would remain slightly warmer than other emmersed sections of the pump...

Ah yes, I do recall seeing a few now. They were about the same time as the Merc Sportjet came out. Nowhere near as successful, athough Merc did have the sense (in the end) to use much larger powerheads even if it was still only a 7.25" pump.. The problems with most problematic jet installs is...

That looks to be a derivitave / in the same class as the HJ212. The HJ212 has a 210mm diameter impeller and Inlet hole of 525mm x 260mm. I would check with Ultrajet what the RPM constraints are for their pump. Swinging a 9.8" axial flow impeller will require a significant amount of torque, of...

Did OMC make a jet? Or was it one of those abortive and problematic (in my opinion) outboard versions? (simply bolt a jet onto an outboard leg and try to capture a new market, which again IMO did jets a rather large dis-service)

With the hp you have available and size / weight of the vessel you may wish to consider the Scottjet, possibly the Flo-pro as well, but at 2.5 tons it is alot to move. As Am Turbine suggested the SD309 would be way to small, and as Baeckmo pointed out wouldn't offer enough thrust for and...

I would fear that as the water inside the tunnel and body freezes that it would expand and crack or break the pump, much like when you put a bottle of beer the freezer for to long...

Clearly mis-informed with limited jet experience, probably with jets in the '70's

Mercury didn't make a 220, they had a 200 (Optimax), 210 (Dual carb, obsolete), 240 (EFI, obsolete), and 250 (Optimax). Interesting that Hamilton Jet don't sell the 212 into the US, however they still send over 900 there every year. The 213 is the same size pump as the 212 (210mm diameter)...

That is unfortunate, the Sportjet (which I am assuming you used as it is drawn in your previous drawing) would have struggled with performance due to the diameter of the pump. Yes they are a nice compact setup and lightweight, simple installation for a production boat (particuarly for guys used...

Had you considered the merits of running the flat area (which we refer to as the 'delta', not sure of the origins but it could be due to the triangular shape) from the transom to just forrard of amidships? The flat area forrard becomes quite narrow so as to minimise the effect of 'slamming' etc...

They return water back to the pump rather than to waste through the exhaust? You could always add a venturi into the tail housing for your purpose

Rupert, how it the build coming along?

Sorry, I don't generally watch ball sports. Though I did notice we have the Webb Ellis cup at the moment! Yeah, a chainsaw and winch can be pretty standard practice here. Saw just recently one of the guys had adapted a capstan and gearbox to bolt onto his saw in place of the chain...