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Author Topic:   Prop suggestions/help for Dauntless 160

cmarques posted 06-18-2005 07:17 PM ET (US)
I'm finally ready to buy a stainless prop and not sure where to start. Here's the basics:
2002 Dauntless 160 (with transom notch)
2002 Mercury 90hp 2 stroke Saltwater series
Stock aluminum quicksilver 13x19 on now
Engine 1 hole up from lowest mounting.
I can turn about 5200-5300 rpm trimmed up and get about 35-36 mph (gps) and burn 9.9-10.1 gph, down from 38-39 when prop was new. (was told by friends that a prop can lose cup over time and cause this but don't know for sure)
I plan on raising the engine up 2 more holes to be 1 from highest mounting (doing this monday after work).
Mercury Prop Selector says I shuold be turning a 26p prop which seems way off from my 19p currently on. I am thinking of going with a Vengeance or a Rapture? prop but don't want to get stuck with something that doesn't work. Do most prop shops/retailers allow exchange if not right and not damaged?
I have some friends,(bass boat types) saying to go with a jack plate but don't know if there would be any pros over cons (extra cost, weight on transom, and extra length to fit in garage) over just raising the engine 2 holes.
I don't want to sound long winded but $300-400 is enough to make me ask a lot of questions.
Thanks
Chris

Marlin posted 06-18-2005 10:01 PM ET (US)
Hi Chris,
With the lower unit gearing on the 90, I think an 18" Vengeance would be the basic choice in stainless. I've read of folks running 20" Laser IIs on Montauks, but I think the acceleration would suffer somewhat on the Dauntless. On my Dauntless with a 115 4-stroke, the highest I can go with the Vengeance is one hole up from the lowest. I'd like to go one more, but the Vengeance ventilates too easily. Eventually I'll try out a 17" Rapture (with the 90, you'd probably want a 19" Rapture).
-Bob
Perry posted 06-18-2005 10:17 PM ET (US)
I agree with Marlin as to prop and I would try raising the motor up one hole at a time.
LHG posted 06-19-2005 12:13 AM ET (US)
If you are turning the 19" aluminum up to full rated RPM, you want a 20" Laser II, with medium vent plugs. Only raise the engine one more hole. You ought to pick up about 4 mph in top speed.
If top speed is less important than fast acceleration or pulling power, go with a 20" High Five.
Buddy's wholesale props, an E-Bay store, sells them for $340 plus about $12 in shipping, no tax. At a price like this, a larger diameter Rapture for about $295 (Cabela's) is not worth it.
Perry posted 06-19-2005 04:31 AM ET (US)
I have always gone down in pitch when going from aluminum to stainless. I experimented with moving up in pitch from stainless but rpm's dropped way too much.
LHG knows Mercury motors and props so perhaps he is on to something.
LHG posted 06-20-2005 05:41 PM ET (US)
Perry, I'm just repeating Mercury's general recommendation.
They say that if you're at the top, or even slightly over, of your RPM max with an aluminum trimmed normally (not out too far and ventilating), go up in pitch. If you're near the lower end, go down.
This may be why, in the mid range 75-125 gearcases, they make the SS performance props in EVEN numbers. That way, you're only going up 1" pitch with SS.
The other situation is that with one of the Laser II or High Five props, you HAVE TO raise the engine up for surface piercing operation. Otherwise, running them fully submerged, as you would an aluminum, you will increase the EFFECTIVE pitch of the prop by 2" because of increased blade drag, particularly with the High Five.
Since lifting the engine generally means an increase in top end speed, it makes sense that you would need turn a slighlty higher pitch to accomplish this. And if you're at the lower RPM end, and drop down in pitch, even this can help, since the efficiency of the SS prop will be better, while at the same time allowing the engine to turn up higher RPM. Either way, the boater wins.
Perry posted 06-20-2005 10:00 PM ET (US)
LHG, I now understand your point but I still think that a 90 HP motor (bare minimum for the heavy Dautless 160) would have a hard time turning a 20" High Five prop no matter how high it is mounted.
cmarques posted 06-20-2005 10:33 PM ET (US)
Thanks for everyone's input! My engine got raised tonight. Brought it over a friend's house and we raised it one hole to start, only took about 20 minutes or so. I am going to to take it out after work tomorrow night depending on the daily downpour and see what difference it makes with my stock prop still on and see if there is any rpm change. I asked a few guys at work and they seem to think the Laser II is the way to go but the numbers will help and tell when I get it on the water.
If I measured right,the bottom of my anit-cav plate sits 1 5/8 inch above the keel line of the boat.
I'll let you all know what happens.
Chris
LHG posted 06-21-2005 04:29 PM ET (US)
Chris, don't expect that aluminum prop to hold too well at that height, as they are not designed for surface piercing operation. But any SS prop you put on will increase your pefromance and top end.
I just took a look at the Mercury prop charts for the 90, running the 2.33 gears, and a 20" Laser II is a prop that runs 38-45MPH speed range. Perry may be right that this is too much prop for your rig, even though the engine is more like a true 98 HP. It's going to be close whether it will work for you. If it does, you will love the prop and better ride and lift it gives.
An 18" Vengeance is a 40 MPH prop on your engine, and that could be what you'll need, but you'll be pushing the new engine mounting height you've gone to. It's also possible a 17" or 19" Rapture or Stilleto would work for you if the Laser II is too much pitch.
Perry, is your Honda 90 running the Mercury lower unit? When the 75 and 90's came out, Honda was buying them from Mercury. Don't know if this still is the situation with the later models. A 4-stroke 90 would run a lower pitch prop than the 2-strokes because of the higher RPM limit
Perry posted 06-21-2005 05:51 PM ET (US)
LHG, I sold that boat with the Honda 90 and yes I believe it did have the Mercury lower unit. The higher RPM range of the 4 stroke would explain why I ran a smaller pitch prop.
The Nantucket I just bought has a new Honda BF135 (same basic motor as the BF150 without VTEC) and I am currently contemplating installing a 14 X 19 Vensura prop but not sure if it is a surface piercing model. Could you go over to the Post-Clasic forum and respond to the thread on Nantucket prop advice? Riverwhaler has the same boat as me with a BF150.
cmarques posted 06-21-2005 09:35 PM ET (US)
I was able to get out for about 30 minutes tonight between rain showers and can say it feels like a new boat so far. I was able to turn a hair over 5400 rpm at a best of 39.5 mph on gps, up from 36-37mph at about 5200 on my last outing. It came right up on plane and very little porpoising at WOT. Looking back I could see my Doel fin planing just above that water with some spray over it- never seen it back there before. I did get some prop blowout trying to trim up running wide open and some in quick turns while trimmed up but couldn't expect that much out my battered aluminum prop. Now I have to figure out which prop is best. Will the Rapture prop (13x19) work o.k. with the engine raised up as it is or should I try the Laser II?
Chris
cmarques posted 06-26-2005 07:18 PM ET (US)
I was out for a few hours today and have some new questions. I borrowed a prop from a friend today and was able to run it for several hours. It is a 13.5x19 stainless, not sure of manufacturer but was off his 115 Honda (probably stock). It seemed to run o.k., good holeshot,planed good and pulled strong but could not turn over 5200 rpm and 38 mph tilted WAY up. He thinks I should use a 19p and raise engine 1 more hole to raise rpm's but I'm not sure I want to go that high (in middle of 5 holes now)
With that prop being a 13 1/2 diameter, will a 13 1/4 as most I've seen for my engine make any signifigant difference in rpm's?
Will raising up 1 more hole be too much?
Why can I get more rpm's out of my stock aluminum 13x19 prop and higher top speed?
Can an aluminum prop lose pitch as it gets beat/worn to make a big change in rpm's?
Why do I ask so many questions?
I think an 18p would get me where I want but haven't seen any advertised except a Vengeance, will it stayed "hooked up" in a high position?
Last one I promise-will a 17p be way too low and over rev?
Thank for everyone's help I hope to find the right prop soon.
Chris
cmarques posted 07-08-2005 08:50 PM ET (US)
Here's my followup so far in my search for a prop.
I decided to go with a Rapture 13.25x19 stainless prop(thanks Marlin). I ordered it last week through www.boat-props.com and got it on tuesday. They have some great specials going right now on quite a few props. I paid $184.95 plus $17.00 shipping which included the prop and the proper hub kit for my Merc 90! It was over $100.00 less than anywhere else I looked.
Headed out for about an hour last night to check out. I took the doel fins off to try first and am able to pull about 5300 rpm but still only about 38.8 mph on gps-still not seeing the higher speeds I hoped for but is in the rpm range I need and no propoising even with the fins removed. I did get some blowout in turns running w.o.t trimmed up but otherwise stayed in the water pretty good. With the engine trimmed completly down it will hit 30mph at 5krpm and accel quickly as trimmed up. It will start planing about 13 mph. It has a pretty good holeshot but revs very quick before jumping up- I'm going to try plugging the vent holes next time out to see what effect there is and maybe reinstall the doel-fins for some experimenting. There is a noticible "rumbling" at idle as I guess most stainless props will do and idle rpm's droppd to about 600- is this too low or should idle be bumped up- it gets smoothed out as hits about 900 rpm in gear. I don't know at this point if I'll try 1 more hole up on the engine mounting or leave as is.
Thanks for everyone's help
Chris

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Author	Topic: Prop suggestions/help for Dauntless 160
cmarques	posted 06-18-2005 07:17 PM ET (US) I'm finally ready to buy a stainless prop and not sure where to start. Here's the basics: 2002 Dauntless 160 (with transom notch) 2002 Mercury 90hp 2 stroke Saltwater series Stock aluminum quicksilver 13x19 on now Engine 1 hole up from lowest mounting. I can turn about 5200-5300 rpm trimmed up and get about 35-36 mph (gps) and burn 9.9-10.1 gph, down from 38-39 when prop was new. (was told by friends that a prop can lose cup over time and cause this but don't know for sure) I plan on raising the engine up 2 more holes to be 1 from highest mounting (doing this monday after work). Mercury Prop Selector says I shuold be turning a 26p prop which seems way off from my 19p currently on. I am thinking of going with a Vengeance or a Rapture? prop but don't want to get stuck with something that doesn't work. Do most prop shops/retailers allow exchange if not right and not damaged? I have some friends,(bass boat types) saying to go with a jack plate but don't know if there would be any pros over cons (extra cost, weight on transom, and extra length to fit in garage) over just raising the engine 2 holes. I don't want to sound long winded but $300-400 is enough to make me ask a lot of questions. Thanks Chris
Marlin	posted 06-18-2005 10:01 PM ET (US) Hi Chris, With the lower unit gearing on the 90, I think an 18" Vengeance would be the basic choice in stainless. I've read of folks running 20" Laser IIs on Montauks, but I think the acceleration would suffer somewhat on the Dauntless. On my Dauntless with a 115 4-stroke, the highest I can go with the Vengeance is one hole up from the lowest. I'd like to go one more, but the Vengeance ventilates too easily. Eventually I'll try out a 17" Rapture (with the 90, you'd probably want a 19" Rapture). -Bob
Perry	posted 06-18-2005 10:17 PM ET (US) I agree with Marlin as to prop and I would try raising the motor up one hole at a time.
LHG	posted 06-19-2005 12:13 AM ET (US) If you are turning the 19" aluminum up to full rated RPM, you want a 20" Laser II, with medium vent plugs. Only raise the engine one more hole. You ought to pick up about 4 mph in top speed. If top speed is less important than fast acceleration or pulling power, go with a 20" High Five. Buddy's wholesale props, an E-Bay store, sells them for $340 plus about $12 in shipping, no tax. At a price like this, a larger diameter Rapture for about $295 (Cabela's) is not worth it.
Perry	posted 06-19-2005 04:31 AM ET (US) I have always gone down in pitch when going from aluminum to stainless. I experimented with moving up in pitch from stainless but rpm's dropped way too much. LHG knows Mercury motors and props so perhaps he is on to something.
LHG	posted 06-20-2005 05:41 PM ET (US) Perry, I'm just repeating Mercury's general recommendation. They say that if you're at the top, or even slightly over, of your RPM max with an aluminum trimmed normally (not out too far and ventilating), go up in pitch. If you're near the lower end, go down. This may be why, in the mid range 75-125 gearcases, they make the SS performance props in EVEN numbers. That way, you're only going up 1" pitch with SS. The other situation is that with one of the Laser II or High Five props, you HAVE TO raise the engine up for surface piercing operation. Otherwise, running them fully submerged, as you would an aluminum, you will increase the EFFECTIVE pitch of the prop by 2" because of increased blade drag, particularly with the High Five. Since lifting the engine generally means an increase in top end speed, it makes sense that you would need turn a slighlty higher pitch to accomplish this. And if you're at the lower RPM end, and drop down in pitch, even this can help, since the efficiency of the SS prop will be better, while at the same time allowing the engine to turn up higher RPM. Either way, the boater wins.
Perry	posted 06-20-2005 10:00 PM ET (US) LHG, I now understand your point but I still think that a 90 HP motor (bare minimum for the heavy Dautless 160) would have a hard time turning a 20" High Five prop no matter how high it is mounted.
cmarques	posted 06-20-2005 10:33 PM ET (US) Thanks for everyone's input! My engine got raised tonight. Brought it over a friend's house and we raised it one hole to start, only took about 20 minutes or so. I am going to to take it out after work tomorrow night depending on the daily downpour and see what difference it makes with my stock prop still on and see if there is any rpm change. I asked a few guys at work and they seem to think the Laser II is the way to go but the numbers will help and tell when I get it on the water. If I measured right,the bottom of my anit-cav plate sits 1 5/8 inch above the keel line of the boat. I'll let you all know what happens. Chris
LHG	posted 06-21-2005 04:29 PM ET (US) Chris, don't expect that aluminum prop to hold too well at that height, as they are not designed for surface piercing operation. But any SS prop you put on will increase your pefromance and top end. I just took a look at the Mercury prop charts for the 90, running the 2.33 gears, and a 20" Laser II is a prop that runs 38-45MPH speed range. Perry may be right that this is too much prop for your rig, even though the engine is more like a true 98 HP. It's going to be close whether it will work for you. If it does, you will love the prop and better ride and lift it gives. An 18" Vengeance is a 40 MPH prop on your engine, and that could be what you'll need, but you'll be pushing the new engine mounting height you've gone to. It's also possible a 17" or 19" Rapture or Stilleto would work for you if the Laser II is too much pitch. Perry, is your Honda 90 running the Mercury lower unit? When the 75 and 90's came out, Honda was buying them from Mercury. Don't know if this still is the situation with the later models. A 4-stroke 90 would run a lower pitch prop than the 2-strokes because of the higher RPM limit
Perry	posted 06-21-2005 05:51 PM ET (US) LHG, I sold that boat with the Honda 90 and yes I believe it did have the Mercury lower unit. The higher RPM range of the 4 stroke would explain why I ran a smaller pitch prop. The Nantucket I just bought has a new Honda BF135 (same basic motor as the BF150 without VTEC) and I am currently contemplating installing a 14 X 19 Vensura prop but not sure if it is a surface piercing model. Could you go over to the Post-Clasic forum and respond to the thread on Nantucket prop advice? Riverwhaler has the same boat as me with a BF150.
cmarques	posted 06-21-2005 09:35 PM ET (US) I was able to get out for about 30 minutes tonight between rain showers and can say it feels like a new boat so far. I was able to turn a hair over 5400 rpm at a best of 39.5 mph on gps, up from 36-37mph at about 5200 on my last outing. It came right up on plane and very little porpoising at WOT. Looking back I could see my Doel fin planing just above that water with some spray over it- never seen it back there before. I did get some prop blowout trying to trim up running wide open and some in quick turns while trimmed up but couldn't expect that much out my battered aluminum prop. Now I have to figure out which prop is best. Will the Rapture prop (13x19) work o.k. with the engine raised up as it is or should I try the Laser II? Chris
cmarques	posted 06-26-2005 07:18 PM ET (US) I was out for a few hours today and have some new questions. I borrowed a prop from a friend today and was able to run it for several hours. It is a 13.5x19 stainless, not sure of manufacturer but was off his 115 Honda (probably stock). It seemed to run o.k., good holeshot,planed good and pulled strong but could not turn over 5200 rpm and 38 mph tilted WAY up. He thinks I should use a 19p and raise engine 1 more hole to raise rpm's but I'm not sure I want to go that high (in middle of 5 holes now) With that prop being a 13 1/2 diameter, will a 13 1/4 as most I've seen for my engine make any signifigant difference in rpm's? Will raising up 1 more hole be too much? Why can I get more rpm's out of my stock aluminum 13x19 prop and higher top speed? Can an aluminum prop lose pitch as it gets beat/worn to make a big change in rpm's? Why do I ask so many questions? I think an 18p would get me where I want but haven't seen any advertised except a Vengeance, will it stayed "hooked up" in a high position? Last one I promise-will a 17p be way too low and over rev? Thank for everyone's help I hope to find the right prop soon. Chris
cmarques	posted 07-08-2005 08:50 PM ET (US) Here's my followup so far in my search for a prop. I decided to go with a Rapture 13.25x19 stainless prop(thanks Marlin). I ordered it last week through www.boat-props.com and got it on tuesday. They have some great specials going right now on quite a few props. I paid $184.95 plus $17.00 shipping which included the prop and the proper hub kit for my Merc 90! It was over $100.00 less than anywhere else I looked. Headed out for about an hour last night to check out. I took the doel fins off to try first and am able to pull about 5300 rpm but still only about 38.8 mph on gps-still not seeing the higher speeds I hoped for but is in the rpm range I need and no propoising even with the fins removed. I did get some blowout in turns running w.o.t trimmed up but otherwise stayed in the water pretty good. With the engine trimmed completly down it will hit 30mph at 5krpm and accel quickly as trimmed up. It will start planing about 13 mph. It has a pretty good holeshot but revs very quick before jumping up- I'm going to try plugging the vent holes next time out to see what effect there is and maybe reinstall the doel-fins for some experimenting. There is a noticible "rumbling" at idle as I guess most stainless props will do and idle rpm's droppd to about 600- is this too low or should idle be bumped up- it gets smoothed out as hits about 900 rpm in gear. I don't know at this point if I'll try 1 more hole up on the engine mounting or leave as is. Thanks for everyone's help Chris