Currently on 19 P. Have plenty power looking for a bit more top end...

Hi Guys.

I have an 18.5 Ft Bowrider with a 91 200 Hp mariner V6. I currently have a 19P Laser II, vented Stainless prop on it, which is what I got when I bought the setup. The boat jumps out of the hole and is very responsive with the slightest touch of the throttle.

When trimmed properly (Just before a rooster tail or a small one) the boat runs at a top end of 52-53 MPH at around 5300-5400 Rpm when trimmed properly, which is what I think is the top end of the rev limit on the motor.

For skiers, tubers and wakeboarders I have plenty of bottom end grunt and have to be careful with the throttle to avoid removing the shoulders from their sockets.

I wondering if a different prop would give me a better top end with a little less bottom end power????

Can anyone suggest a change or do I have the optimum setup at present?

Hi All.

I never got any replies on this one so I will give an update to anyone who may find it useful.

Not wanting splash out I looked around for ages and eventually found a used 22 Stainless from Suzuki for around 50 Dollars in fantastic condition. It has built in vents and when the boat was in for service I got the mech to fit if for me.

He played with the depth of the thrust washer and I had to get a new washer for the front of the prop, but it worked and how.

My top end WOT speed is now up from 53 MPH to 62 MPH at the same top end RPM.... Next one is going to be a 23... as with the 22 it gets there in a matter of seconds and I know it's got more to give on the top end.

The fast hole shot is your vented function working for you. Since both props were vented you realized great hole shots even though you upped the pitch. 200 hp on an 18 1/2 bow rider assumed to be deep V glass is a fast setup. I ran a 125 on one back in '72 when engines were power head rated (10-15% less prop hp that todays rating) and it was plenty of hp for the boat.

One aspect of most deep V designs is that the V is equipped with little steps along the V called "lifting strakes". They are like little water skis and the faster you go the water pressure increases against them and the hull lifts higher out of the water reducing drag and giving you more mph from the same engine/prop.

One of the things that changes is the prop slip. Props (basically a screw thread) slip when they turn as water is not a solid like jello if you will. That being the case, a high performance prop like the Laser II, of which I am familiar, is designed with high rake (blades bent back) to raise the bow (bow lift) reducing the hull to water contact and reducing drag/friction getting more mph from a given package. The prop is cupped meaning the trailing edge of the blades are a higher pitch or bent over more than the remainder of the blade helping the prop to hold onto the water and slip less at high trim angles running close to the surface. The ports (holes) are to unload the engine in the hole shot where the load on the engine is max. 2 strokes like to run not lug. By venting exhaust gasses over the blades, you reduce the density of the water thus reducing the load on the engine which enables it to rev up to higher rpms faster thus developing your engine hp faster and thus a faster hole shot. Water pressure seal off the holes at planing speeds and their effect is nil.

So, you prop for top end and it sounds like you are moving right along. On rpms, my '94 sales brochure show the Mariner 200 to come in 4 packages, 2 regular and 2 high performance, the difference being 200 more rpms on the Magnum EFI and the Offshore models. So they list the operating WOT range at 5000 to 5600 and 5000 to 5800.

Seems your hull is working for you in doing what I said to reduce drag as speed increases allowing you to pitch higher yet maintain the load (rpms) on the engine. Obviously there is a limit and that will be when your WOT rpms fall off. Your 23 may put you over the hill so to speak but you know not till you try it. That is all you are going to get unless you change something else.

HTH,
Mark

HI Mark. Thanks for the detailed information.

I'm going out over the weekend again and will give this a full run. The lake I tested it on the other day was small and going at 60 + mph I was reaching one side from the other far too quickly to really stretch the legs out.

I'm also wanting to try a skier and tuber or two with the new prop, with a few passengers to make sure I still have enough out of the hole, which I am sure I do before I go any larger.

I'll report back and try to make a vid to post for interest sake as well.

Keithm18 said:

HI Mark. Thanks for the detailed information.

I'm going out over the weekend again and will give this a full run. The lake I tested it on the other day was small and going at 60 + mph I was reaching one side from the other far too quickly to really stretch the legs out.

I'm also wanting to try a skier and tuber or two with the new prop, with a few passengers to make sure I still have enough out of the hole, which I am sure I do before I go any larger.

I'll report back and try to make a vid to post for interest sake as well.

Click to expand...

If you are talking about water toys and top end, the two don't communicate. You have to prop for one or the other, sorry but that's the way it is.

Mark