Ignition and prop Questions

[ruben]

Hi Guys,

I have an 87 Four Winns 170 Horizon (17ft) OMC
It has a 2002 4.3L out of a Chevy Blazer. Edlbrock 600 carb and a Edlbrock performer manifold.(rated at 190hp at 4400rpm --250lbs tq at 2800rpm with efi in the blazer)

It actually runs a bit better than the original 205hp that was originally in the boat.

First Question: at 100 degree day with 3/4 tank of gas and 700 lbs of people in the boat, it has a very hard time getting me out of the water(200lbs) on a single ski. top speed is 44mph at 4300rpm with 900lbs of passengers.the prop is a 14 1/2 x 19.

What is your recommended prop to get a skier up with this much weight in the boat?


I figured out my ignition question
thanks

[ruben]

Anyone!!

[alex fletcher]

ruben the way I see it is You and the Boat Both start to plan at the same time
so we have to look at the Prop as more of a displacement Prop then a planing Prop.meaning it would be flatter with very little cupping Do you own a small angle grinder? or see a pro. if 4300 rpm is the boat top speed unladen you are over pitched

[ruben]

thanks for the reply Alex.

Im not really sure of the actural rpm of the engine.

at 42mph the boat tach says 5200rpm. and my MAC Tools multimeter says 4000rpm.

what should the rpm be at 42mph with this prop and 1.84 gear set?


Now with 2 people in the boat it will go 48-50mph or so.

but most of the time I have 4-5 people in the boat when we ski.

Yes I have a grinder.

thanks

[Jango]

With about 10% slip, 42 MPH with a 19p. cupped prop your RPM will be 4500 - 4550. If 4 people will be the norm when you Ski. I would suggest a 4 Blade prop. You may have to drop 1" of pitch with the 4 blade.

[alex fletcher]

Got to say with 4-5 people and a skier you must be close to over loaded six in a 17 ft boat can I suggest a larger boat Even so Jango's right 4 blade may be the way to go but you may have to drop 2 inches in pitch and throttle back when not skiing and you will lose a knot or two

[ruben]

what do you think of the hinged devices that you bolt to the outdrive to help it get on plane quicker?

[alex fletcher]

Foils, trim tab or wings wont do a thing, you have to address the fundamental problem, loaded up the Boat bogs down due to to much whight. Either lighten the boat, get a bigger engine, or reduce the pitch of the prop, or increase the gearbox reduction ratio.
sorry but I think that they are your only options

[stonebreaker]

You might try a different launch technique when you slalom, too. When I was younger, we skied behind my dad's bass boat. The boat was fiberglass, 18 feet long, with an 85 hp outboard, and barely managed 30 mph when pulling a skier. I found that I was able to get up on plane much quicker and with less fatigue in my hands if I bent my knees and stayed as close to the ski as possible, putting as much weight as I could over my front foot and even pulling up with my back foot to keep the ski as parallel to the water's surface as I could. This kept more of the ski in the water, which meant that I would get up on plane that much quicker. It was a little awkward at first, but once I got up to speed I could ski a lot longer before my hands got tired.

Another technique we used when we got bigger was stretching out the rope, then turning the boat 90 degrees before we launched. It was REAL hard to learn that one, but it let the boat get going before having to pull up the skier, and it didn't yank you over on your face like it would if you started with a slack rope.

[gonzo]

If you have a motor right out of a truck, the camshaft, timing and other parts are incorrect and will never give you the low RPM torque you need.

[stonebreaker]

Originally Posted by gonzo

If you have a motor right out of a truck, the camshaft, timing and other parts are incorrect and will never give you the low RPM torque you need.

Are we going to have to go through this again? The truck cam makes more torque than the marine cam below 3000 rpm. Marine engines are not the be-all and end-all torque monsters you seem to think they are. Look it up on www.gmpowertrain.com and please verify your info before you go spouting bad info all over the forum again.

Hell, I'll post the links for you. Straight from the manufacturer.
marine engine
truck engine

[ruben]

Originally I had a roller cam 2bbl motor that I put on an edelbrock 4bbl and manifold.

Now I have this 2002 injected vortec headed engine out of a blazer that I put a edelbrock manifold and 4bbl on.

The new motor pulls better all the way around, even though the cam is smaller.
Due to the vortec heads.

I wonder how it would run with the roller cam out of the original motor?

does anyone know if the 2bbl roller cam is the same cam as the 4bbl roller cam in the earlier OMC engines?

[mattcat79]

ok does any one know why my trailer trim up buttons when pushed stay on and wont shut off unless i disconect the battery. cuold it be the cylinoid. thanks

[ruben]

Matcat79,

You should have posted your unrelated question in a new post(new thread)

You probably will get better response that way

[gonzo]

Stonebreaker is a computer geek(by his own description) that doesn't even own a boat. He does find all kinds of links to manufacturers which he claims, in other threads, are not to be trusted.