EGT and mechanical B series

[Woo]

Following some interesting observations I have some questions.

Boat has a pair of 370B remans.
SBMar upgrades prior to install, and every box ticked for a proper install.
Exhausts show very little back pressure.
Engines achieve 100rpm over the rated 3,000 consistently at full throttle.

Please keep in mind that my EGT readings might appear high in isolation, (however when I shift the probe to the opposite side of the turbo outlet elbow they’re significantly lower by the order of around 15%). The exhaust blankets I have don’t allow me to readily leave them in the “cooler” spot.

That said, let’s look at the figures I give you as I’m looking at feedback NOT on outright temps but on variations in temps at different rpm. Values converted from celcius.

2,000rpm – 970*
2,200rpm – 1010* This is an ideal rough water cruise speed and ecenomical long distance speed for us but remaining at this rpm with the EGT spike concerns me a little.
2,300rpm – 1010*
2,400rpm – 995*
2,500rpm – 975*
2,600rpm – 960*
2,700rpm – 960*
2,800rpm – 950*
3,000rpm – 950*
3,100rpm – 950*

What do you make of that and is that variation seen at those rpms “typical”? For what it’s worth, the hull “feels” really happy from 2,500/2,600 up, it’s a deep V planing boat with a shape like it’s a big Formula 233.

Topic

[Woo]

I failed to respond to this earlier, so my apologies.

Each 100rpm closely transfers to 1 knot of boat speed.
So 600rpm = 6 knots,
2,000rpm = 20kn,
2,600rpm = 26kn and
3,100rpm = 31kn.
This is quite accurate except around the transition to planing speeds.

She’s planing cleanly by 15kn when throttling up, and will hold plane down to around 12kn with a bit of tab in reasonable weather.

[Tony Athens]

Measured exhaust pressure at various RPM’s? “show very little” means nothing.

Vessel speeds at those RPM’s you referenced?

Just because to reach “100 over”, does not mean you are loading properly at “vessel cruise speeds’ ( not RPM’s) as to where the vessel feels happy.

Rob may be on the right track..

Tony

[Rob Schepis]

Just seems to me she’s feeling the load of not being on a fully clean & efficient plane when running at those higher EGT rpms, especially considering that hull type you describe…

[Author]

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