First drive impressions and questions

[bobo4030]

Just took my first ride in my Alumacraft Classic 165 (Big) tiller with a Mercury 60 hp 4 stroke. Prop is a 10 5/8- 12 pitch 4 blade Spitfire. The motor is mounted in the center hole of 5 positions.

I love the rig. The Terrova 80 with I-Pilot was a great choice. With everyone's help on WC, I mounted the Terrova and the Mercury Smartcraft tach. The tach provides so much important information, it's ridiculous.

After an hour, I couldn't resist a quick top speed run? Just me, 10 gallons of gas and rigged to fish I hit 34 mph (gps) at 6250 rpm. On plane, there is a huge amount of water being sprayed 5 feet into the air on both sides of the lower unit, adjacent to the transom.
Mercury performance bulletins suggest the motor to be mounted in bolt hole #2. At speed, the cavitation? plate appears to be about 2 inches under water. From what I've read here, that's too deep.

Questions:
Will the addition of another passenger and his gear(maybe 300 lbs) drop the rpm into the factory WOT rpm range of 5500-6000?
Do I need to raise the motor to get the most performance and efficiency? The boat handles fine, but all that water at the transom seems wrong.

Thanks in advance for any advice.

Rick

[yarcraft91]

When I got my new Alumacraft Yukon 165CS/50 Merc EFI, it also threw huge amounts of spray on-plane. The motor was mounted as low as it could go and that was the problem. The anticavitation plate was throwing that spray up into the air, because the plate was buried in the water. Once I raised the motor (1 hole in my case), the spray pattern became more normal.

If you're getting 34 mph and 6250 rpm, you are under-propped for the load you had. Raising the motor will increase WOT rpm. Consider moving to a 13 or 14 pitch prop after you raise the motor. I run a 13 on my 50 horse, good for 6000 rpm with just me and a normal fishing load in the boat.

[bobo4030]

Originally Posted by yarcraft91

If you're getting 34 mph and 6250 rpm, you are under-propped for the load you had. Raising the motor will increase WOT rpm. Consider moving to a 13 or 14 pitch prop after you raise the motor. I run a 13 on my 50 horse, good for 6000 rpm with just me and a normal fishing load in the boat.

Yar,
I suspected the WOT rpm would increase if I raised the motor. I chose props (one 3-blade Black Max and one 4-blade Spitfire) based on Merc's performance bulletins for the same boat and motor. No small investment for me. I'll be doing more testing. I need to get the boat fully loaded to see if I am truly under-propped. If I decide I need a different prop, how do you test drive props without buying them? And what to do with the 2 brand new ones I already have.

Thanks for the reply.

Rick

[yarcraft91]

Check with local people who sell props. Hopefully, you can find one who is cooperative. When I was testing my boat, I could take a prop from one dealer's shop, try it and return it for a different pitch, as long as the returned prop was undamaged. I tested and returned 2 before getting it right. You may be able to swap your current props for same type, different pitch. Dealer who sold you the boat is where to start.

[REW]

If you have two brand new props, just take your receipt and prop back to the seller and request a refund or prop exchange for a different prop.

In your case for your boat, I would raise the motor to the top hole, put on a 14 or 15 pitch 3 blade prop and see how it goes. If you get blow out or prop cavitation, start dropping the motor - one hole at a time until you get the motor where you need it.

Also, when the motor is where it needs to be- adjust the prop pitch until you get it where it needs to be.

General rule of thumb - never buy a prop, until you find out exactly what prop you need for your rig, load, driving style and motor.

I have found on many boats and motors that the cavitation plate can run at a height that is several inches ABOVE the bottom of the hull.

Some can't, but many can. If your hull design is such that the motor can run that high, then by all means run it that high.

Run the motor as high as you can, and still have good prop hook up, no venting in turns of average size and the ability to work big waves and water without having the prop blow out. Then, use the prop that works best for your rig, gives you the right rpm, hole shot and top speed that you can live with.

Remember, any time you want hole shot, you give up on top end.
If you want the ultimate top end, you will always give up hole shot.

Most folks set up their rigs for a balance, or even a bit of a nod towards hole shot - rather than top speed. If the boat is used mainly for fishing, and if rough water is often encountered, top speed will seldom be used, but hole shot will be needed all of the time.

Good luck
REW

[REW]

Rick,
By the way, when you open the throttle, are you trimming the motor as high as you can without having the prop blow out, or having the boat porpoise or bounce?

If not, do some running and try to trim as high as the motor will allow, or until you have the prop completely blow out.

When, you find that point, just bump the trim back down a bit for the sweet spot when running.

Good luck
REW

[bobo4030]

The props were ordered as part of the boat purchase. Chose the ones I did based on Mercury's performance bulletins. Live and learn. I have lots of testing ahead of me. All great ideas,Guys. Thanks

Rick

[Munshaw]

I think that's pret good speed for that motor and hull. I had a Navigator 165 tiller with a 60 4 stroke and a 13 p prop and it would do 32 mph with just me in the boat, and my 24 v Terrova with two group 27 in the bow.

Nice boat though, I miss my tiller sometimes....

[bobo4030]

First tiller for me. Makes you feel like a real man sitting right out there in the open. Better pack the rain gear for the windy days.

Rick