Mercruiser 1.7 Diesel in a 6m Rib

[Andre]

Originally Posted by simmons0

If your around the solent for the charity cruise ill show you 40 knots+ for yourself.
Racing a friends boat in small chop with 3 people and 80 littres of diesel we hit 43knots and on the boats maiden voyage up the river from fareham hit 47.7knots with barely any fuel, a few knots of tide and Kevin from solent ribs driving.

This is with a 23inch Ali prop reving at 4500-4600 rpm.

edit: I did have a photo of 43knots on the gps somewhere. Ill see what i can do.

David

reving at 4500-4600 is above the manufactures advice and for sure not doing the engine any good for long periods of time. I also tried the 23" prop but s/s and was over reving so went back to the 21" and max rev permitted from memory is 4200/4400. I prefer to stick to max 4000/4100 and not for long period of time

your rib is smaller and for sure much lighter then my Parker 630 so higher speed is possible

[simmons0]

Harry now,
The book says 4500rpm max, Lee says 4600 max, either way we only ever run the boat flat out for very short periods of time and tend to cruise below 3500rpm.

[RIVA]

a calabrated speed gun

[Andre]

Originally Posted by simmons0

Harry now,
The book says 4500rpm max, Lee says 4600 max, either way we only ever run the boat flat out for very short periods of time and tend to cruise below 3500rpm.

Hi Harry

Don't know what book you are refering to but the official Mercury/MerCruiser operation, maintenance & warranty manual on page 50 says rated RPM at WOT 4000-4400RPM and I cannot find any reference to 4500 max. It doesn't matter what Lee says it what the good book says as it is a factory warranty and not Lee's