Prop or jack plate help slow plane on 201 pro

[463double]

Hey guys, need some info. I have a stratos 201 pro 21ft with a 200 Mercury XRI EFI. It had a Mercury High 5 prop 21 pitch 5 blade which was great out of the hole but top end is about 50 mph at 5900 RPM. it also had a problem with porposing at lower speeds. I went to a Power tech 25 ptich 4 blade prop and now i have planing problems when the boat is loaded. My jack plate has the motor up a good bit. i would have to measure for more accuracy. Once i get on plane i run about 57 MPH turning about 5400RPM. Can i adjust the jack plate to help this problem with boat not planing or do I still have a prop problem. This boat is heavy and with both tanks full and livewells full she struggles to get on plane. Any advice without having to buy another prop.

 

[SparkieBoat]

Re: Prop or jack plate help slow plane on 201 pro

you need trim tabs...for sure..get the motor as high as you can get it without the prop blowing out.

 

[Texasmark]

Re: Prop or jack plate help slow plane on 201 pro

Is your current prop ported? If not, porting will help and the size of the hole will determine the amount of slip...the larger the more the cavitation and engine unloading and rpm's come up faster and the better the hole shot (to a point) and then at WOT, the ports are sealed by water pressure in the slip stream and effectively disappear leaving your top speed/rpm pretty much where they are.

I have a prop (Ballistic XP) that I ported with 1/4" (small) holes and got a much better hole shot, but not a lot of revving (cavitation), nice smooth plane out and up the speed ramp. Top end actually increased about 1 mph and rpm's went up from 5600 to 5800. So, I guess I was still on the rise of the power curve at 5600 and at WOT actually did get some engine unloading which allowed the rpm's to increase giving me some additional prop revs.

I think it's the Quicksilver/Merc Laser II that has hugh holes and plastic plugs to size down as you desire. The big holes would give you a lot of rpm's fast with a whole lot of prop slip, but should get a big load up fast. Then as the boat picks up speed, at some point the holes will seal off and the prop will grab solid water, load up, and away you go.....like overdrive in a car. I had a Laser (I think it was a Laser, had it on my Merc) back in '89 with smaller holes than the Laser II, don't remember the diameter, but it would do that, really neat. That engine (115 tower) ran at 6k and loved it.

HTH,

Mark

 

[463double]

Re: Prop or jack plate help slow plane on 201 pro

Is your current prop ported? If not, porting will help and the size of the hole will determine the amount of slip...the larger the more the cavitation and engine unloading and rpm's come up faster and the better the hole shot (to a point) and then at WOT, the ports are sealed by water pressure in the slip stream and effectively disappear leaving your top speed/rpm pretty much where they are.

I have a prop (Ballistic XP) that I ported with 1/4" (small) holes and got a much better hole shot, but not a lot of revving (cavitation), nice smooth plane out and up the speed ramp. Top end actually increased about 1 mph and rpm's went up from 5600 to 5800. So, I guess I was still on the rise of the power curve at 5600 and at WOT actually did get some engine unloading which allowed the rpm's to increase giving me some additional prop revs.

I think it's the Quicksilver/Merc Laser II that has hugh holes and plastic plugs to size down as you desire. The big holes would give you a lot of rpm's fast with a whole lot of prop slip, but should get a big load up fast. Then as the boat picks up speed, at some point the holes will seal off and the prop will grab solid water, load up, and away you go.....like overdrive in a car. I had a Laser (I think it was a Laser, had it on my Merc) back in '89 with smaller holes than the Laser II, don't remember the diameter, but it would do that, really neat. That engine (115 tower) ran at 6k and loved it.

HTH,

Mark

It is ported i just wonder if bigger holes would help. I seem to not have enough RPM. i will check the holes but i think they are around 3/8 or even a 1/2. Thanks

 

[463double]

Re: Prop or jack plate help slow plane on 201 pro

Im sure trim tabs would help I just have a hard time putting them on a bass boat.

 

[SparkieBoat]

Re: Prop or jack plate help slow plane on 201 pro

trim tabs will do more than just help..they will make a big difference. you already have your motor propped right, changing props will make at best a minimal difference, and may even get worse.

 

[Texasmark]

Re: Prop or jack plate help slow plane on 201 pro

It is ported i just wonder if bigger holes would help. I seem to not have enough RPM. i will check the holes but i think they are around 3/8 or even a 1/2. Thanks

In reading up on the Laser II I guess the reason they went with the large diameter holes and reduction plugs was for different applications. Would imagine the largest hole (hole bored in the prop) would give you a good hole shot on one load but would overly cavitate on the opposite load....trying to figure out which is which....big holes for a heavy boat or small holes. Then the hole reducing plastic plugs would be for the variances between those two extremes.

The holes I had in my Laser (I) caused the engine to noticeably rev in the hole shot, not overly as I got on plane fast, but you could tell the prop was getting air (exhaust). Don't remember the diameter of the holes. The boat had a pretty deep v with a pad and being a Ranger was quite heavy so the engine was working pretty hard to get her up.

On the current boat, flatter bottom and much lighter, the 1/4" holes I drilled help the hole shot but I didn't notice any overrevving and I didn't notice the "lock up" of the prop after I got up to speed that the Laser provided.

Best I can do,

Mark

 

[463double]

Re: Prop or jack plate help slow plane on 201 pro

In reading up on the Laser II I guess the reason they went with the large diameter holes and reduction plugs was for different applications. Would imagine the largest hole (hole bored in the prop) would give you a good hole shot on one load but would overly cavitate on the opposite load....trying to figure out which is which....big holes for a heavy boat or small holes. Then the hole reducing plastic plugs would be for the variances between those two extremes.

The holes I had in my Laser (I) caused the engine to noticeably rev in the hole shot, not overly as I got on plane fast, but you could tell the prop was getting air (exhaust). Don't remember the diameter of the holes. The boat had a pretty deep v with a pad and being a Ranger was quite heavy so the engine was working pretty hard to get her up.

On the current boat, flatter bottom and much lighter, the 1/4" holes I drilled help the hole shot but I didn't notice any overrevving and I didn't notice the "lock up" of the prop after I got up to speed that the Laser provided.

Best I can do,

Mark

Thanks again i will do some testing and look in to all these areas, This was some great info that I have picked up on. I will let you know how it goes. I did some measuring and I may need to raise the motor slightly according to my prop guy. He says i have alot of drag. Thanks guys!

 

[Texasmark]

Re: Prop or jack plate help slow plane on 201 pro

I did some measuring and I may need to raise the motor slightly according to my prop guy. He says i have alot of drag. Thanks guys!

I had one boat that I raised the engine one notch that I recall off the transom. It was a 15' Kingfisher that I referred to in the 70 hp thread above and having a flat transom, it made a noticeable difference....whereas on a deep V it may not have made that much difference (don't know). Raising the engine allowed me to up my prop pitch 2" and the boat was not the same old critter....really livened things up.

Mark

 

[SparkieBoat]

Re: Prop or jack plate help slow plane on 201 pro

you should basically raise your motor as high as you can with out the prop blowing out..a good place to start is getting your cav plate about 1 or 2 inches above the bottom of the hull, this could be too high but maybe not. here is a pic.