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Old 10-02-2017, 11:16 PM   #21
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I have Detroit mains and bypass part of the water. I use a cheap heat measuring gun on the exhaust piping to check temps. My exhaust exits the stern, about 30' behind the engine so I measure temps along the way to be sure. Set once and never had to reset. You must have a cheap Chinese tool store in Australia. Canada has them. I also have a 3/8" line to each stuffing box for cooling.
The heat gun is a good investment. If you don't have one they're good for checking electrical connections and exhaust temps. I don't have individual cylinder pyrometers and use the gun to tune the cylinders.
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Old 10-03-2017, 12:47 AM   #22
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Lots of IR heat guns in OZ. Shops,and Ebay. Mine works great, around $20AUD. But I think the issue is balancing the bypass and the water exiting with the gases, and regulating the flows to get it right. I`d assume anyone working to that end, and most boatowners and mechanics, would have an IR gun.
Even if the "mechanic" who recently surveyed my boat didn`t bring one.
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Old 10-16-2017, 04:36 AM   #23
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Peoples.

We have completed sea trials number two of engine conversion. We ended up opening the gate valve completely to divert 2 inch hose worth of water past the exhaust. These pumps do put out a lot of water. As the HP per L of capacity is high they need high volumes of water for the heat exchangers.

I may remove the valve but is it nor required.

Back pressure is within the factory specifications. Towards the high side at full noise but I don't expect to run for any length of time at this speed. But still within specifications.

Temps on the exhaust are all acceptable. Max temp at max RPM was 41C on the gas side of the pong box.

Also tested temps after return to idle (as the pump backs off) and no raise of this temp with it falling back to 29c in about 10 seconds.

All other locations are lower then this.

Good news no modifications required to existing exhaust.

Two issues.

1. Max RPM not attained only 2130 out of possible 2400... So prop is coming off for visit to prop shop...

2. Initial kick into gear causes RPM to drop off from 600 to 550 before it come back about 4 seconds. This causes vibration. Never had this issue on old motor which was 18L V8. My engine technican says the newer 13L inline 6 has less inertia this is why it is visible.

When the prop is re-pitched we will retest to see if reduced pitch helps.... I think ultimate solution will be either Idle RPM increase of some smart software to bump up the RPM as the actuator selects gears...

Attached photos of bypass at max RPM and 3 inch raw water intake on engine.

Attached video but now sure if it will work.
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Old 10-16-2017, 04:40 AM   #24
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https://youtu.be/0MKMUu-kjAo
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Old 10-16-2017, 08:49 AM   #25
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The RPM drop is not acceptable IMHO. Something is amiss and I can only but guess what, starting with the fueling system controls. Does bumping idle up a bit change things? Hold their feet to the fire.
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Old 10-17-2017, 05:45 AM   #26
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1. Max RPM not attained only 2130 out of possible 2400... So prop is coming off for visit to prop shop...

What RPM is seen in neutral at WOT?

" Initial kick into gear causes RPM to drop off from 600 to 550 before it come back about 4 seconds. This causes vibration. Never had this issue on old motor which was 18L V8. My engine technican says the newer 13L inline 6 has less inertia this is why it is visible."

The mass of the running gear starting or reversing becomes a tiny overload , slowing down is normal with a modern lighter engine mass.

Only becomes a problem if the engine stalls when shifting from F to R.
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Old 12-06-2017, 06:44 AM   #27
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Update

Prop was adjusted from a crude 39inch pitch back to 34inch and nicely balanced. We are now pulling 2380rpm WOT for 26knots. Back pressure is at top of allowed max at WOT. This was full fuel with all toys on board.

As we are pleasure rated I will limit my top rpm to 2200. Ultimately I would like a new prop but that a bigger investment at this stage.

Typical cruise is 1650rpm which give about 15 knots and 30L per hour on the gauge. 1950 gives 18knots at 45L per hour. These are not verified but what the engine management gauge is showing. I have a 250nm trip planned over holiday break and will see how we go. Only 15 more sleeps.

Interestingly at 900rpm we do about 10knot for 10L per hour.

Gate valve was removed as no regulation of bypass is required. Exhaust temps of pong box and piping is not higher then 40C or about 104F.

My takeaway

High cooling requirements of new high HP for displacement (more heat) means raw water flow is high and retrofitting to existing boat requires diversion or exhaust size increase. In this case diversion was easier and cheaper.

It surprising how little water is required to keep the exhaust cool.

A balanced and blueprinted prop is noticeable smoother but that is subjective... It seams like it is anyways.

I changed from 700hp at 2200 rpm with 18L
to 825hp at 2400 rpm from 12.9L
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Old 12-08-2017, 11:16 PM   #28
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Still looking for your WOT IN NEUTRAL rpm.
Your prop cannot be considered until you are sure that the motor can attain max rated rpm. If the motor won’t reach rated rpm, you have work to do before adjusting propeller dimensions.
I would keep the valve, any thru hull should have one.
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Old 12-09-2017, 06:14 AM   #29
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"
"Back pressure is within the factory specifications. Towards the high side at full noise but I don't expect to run for any length of time at this speed. But still within specifications."

When the exhaust has to push a lot of water out the exhaust it takes power , and burns more fuel.

Perhaps lowering the water flow thru the exhaust will allow higher RPM.
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