60 Big Foot EFI Motor Setup

[dicko1980]

Hi guys,

I've just fitted a new 60EFI Four Stroke Big Foot to my 5m Hooker. The boat was originally powered by a two stroke 75, so HP wasn't an issue. Now that I've switched over to the Four Stroke I'm wanting peoples opinion on the motor setup as I am trying to achieve the best setup possible. I know the 60 will never have the sting as the 75 but I want the motor to be as efficient as possible. At present the motor is on the third set of holes from the top down and the cav plate is 25mm below the bottom of the hull when motor is fully trimmed in. I am spinning a 13 and one quarter by 14" pitch S/S Vengence Prop as a test prop. At present the motor had only 4.5 hours on it. At 4500rpm I am getting around 17-19knots cruise depending on conditions. When the throttle is opened up I can pull 5600rpm at 25-27knots. I find the boat now is a lot more sensitive to trim and that when winding on the throttle out to around 4500rpm there is a lot of water being sprayed up the leg and bottom of cowl. These test runs were all done in the ocean in about 10-15knots conditions, 100L of fuel, 160L esky filled half with water as ballast load, and two people at around 160kg combined. I found coming home today whilst punching through chop the motor would drop around 200-300rpm depending on size of wave. This was cruising at 4400-4500rpm at around 15-18knts. My questions are do I raise the motor up a hole to see if I can stop the water spray or do I just live with trimming the motor out? And would do I change props or wait for the motor to loosen up to pick up a few more revs?

Thanks
dicko1980

[Noelm]

I am thinking that to raise it one hole at a time will be the way to go,if there is water spraying up then it may be way too low, trial and error is the way to go, get the height correct first, then the prop size and your set!

[FNQCairns]

I am thinking that to raise it one hole at a time will be the way to go,if there is water spraying up then it may be way too low, trial and error is the way to go, get the height correct first, then the prop size and your set!

Yeah that's the way to go, If it ventilates a little when sloppy outside see if you can live with it for the efficiency gains, need to re-asses somewhat when the new set of numbers comes in, is the top of your rev range 6000? for that engine suspect you will need to look at another prop (stuff all around that will fit your nich)- although you could work the cup away (especially), diameter (possibly) on that one (13, 3/8?) they have a lot of blade surface area for diameter, still need to wait till you get the next test done.

If you get another 100rpm from eliminating cup, near 100 from engine height rise, 100 from the engine loosening up over a few hours....think you are close, each gain will vary, with luck the sum will end up very close to where you need to be without 'tipping' the prop diameter but the idea is an option to stay with the same prop and keep costs down, dont think you will do better with any off the shelf prop without trying a lot of different brands.


cheers fnq

[dicko1980]

Motor is actually bolted through the second set of holes from the top down instead of the third set like I posted. I was looking at the top mounting brackets on the outboard by mistake.

dicko1980

[yamp]

Dicko the old mans just brought the same setup but hes got a 60 high thrust Yammie on it , his jumps on the plane quick but its not that quick,top speed of 24knts at 6000rpm trimmed out,does 20knts at 5400rmp once you start to drop more revs its starts to drop off the plane at 4200rpm approx,the prop looks like yammi original 13 pitch not sure diameter,spoke to solas props re performance they said to look at motor height first cav plate sould be skimming surface of water when running trimmed out,I will have to check it out when I get back from holidays in a couple of weeks,I let you know what I work out and if you come up with anything in the meantime it would be great if you could pass it on cheers Yamp

[dicko1980]

Hi Yamp,

I spoke to the guys at Hooker before I went ahead and ordered the motor and also to another couple of boys with 60 powered Hookers. From what I was told I should be able to get a tad just on 30 knots top end. All the boys with the high thrust yammies have their motor height setup on the second hole down from the top of the bottom bracket. I am going to lift my motor up another hole to see if I can correct all the water spray up the side of the leg and powerhead when the motor is fully trimmed out. I would talk to the guys at Hooker and I will you know how I go and how my mate is going with his setup with the new high thrust. Just a matter of interest how loud is the motor whilst revving out. The merc is dead quite at idle but I find that it not as quite as I thought a four stroke would be when under way.

Cheers
Rob

Dicko the old mans just brought the same setup but hes got a 60 high thrust Yammie on it , his jumps on the plane quick but its not that quick,top speed of 24knts at 6000rpm trimmed out,does 20knts at 5400rmp once you start to drop more revs its starts to drop off the plane at 4200rpm approx,the prop looks like yammi original 13 pitch not sure diameter,spoke to solas props re performance they said to look at motor height first cav plate sould be skimming surface of water when running trimmed out,I will have to check it out when I get back from holidays in a couple of weeks,I let you know what I work out and if you come up with anything in the meantime it would be great if you could pass it on cheers Yamp