Using transom "wedges" on an 18 Outrage with jack plate

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Author Topic:   Using transom "wedges" on an 18 Outrage with jack plate

ewalsh posted 09-12-2007 07:27 PM ET (US)
Hi gang,
The SlideMaster brand 6" jack plate I just got came with a set of alluminum "wedges" that I was told effectively shim the jack plate off the transom.
My boat is a classic Outrage 18 with a 150hp Johnson 2 stroke.
I have 3 questions.
- What do they do for the boat's operating performance?
- How are they installed between the transom and jack plate?
- Should they be used with my application?
Thanks a lot!
Ed

Sal DiMercurio posted 09-12-2007 10:45 PM ET (US)
You don't need them with your boat.
Those wedges are for transoms that have far more deadrise than yours, & the wedges are inserted between the jack plate & the transom to push the bottom of the plate out, away from the boat, otherwise you would have to run your engine at about 2/3 - 3/4 trim out just to keep the boat level.
Without the wedges on another type of boat, the boat would ride to flat, with little chance of even trimming up enough to get the boat to porpoise, because the lower unit would darn near be right under the transom.
Again, they "aren't" for your application.
Sal
Kevchap posted 09-13-2007 09:12 AM ET (US)
I have the exact boat, motor and jackplate you do. I installed my jackplate without the wedges and it works wonderful. I agree with Sal.
As I stated before my rig has the cav plate 1.5 inches above the keel. This set up works well with a generic alum prop for all around driveabilty, although I'm sure it's not the fastest set up possible. I'm planning on experimenting with raising the motor this weekend and I'm still shopping for the "perfect" prop. My goal is 50 Mph WOT and 40 MPh at 4000. I'm presently at 47 MPH WOT [light load]and 36 Mph at 4000 so this goal is lofty.
ewalsh posted 09-14-2007 01:39 PM ET (US)
Sal - thanks you for your advice. I'll take it!
Kevchap - thanks as well. What prop are you currently running?
Thanks, Ed
Kevchap posted 09-14-2007 04:56 PM ET (US)
Michigan 14.5 x 19 Alum. It's just to get me going and will become a spare. I'm in search of a good SS prop. I believe 19" is the right pitch for this engine, 17" turns to many rpm's and is hard on mpg.
Sal DiMercurio posted 09-14-2007 10:24 PM ET (US)
That engine needs to reach 5500 rpms @ wot.
My thoughts are a 17p omc s/s.
Or try a 14.25 x 15 or 17P Stiletto.
You will be able to raise the engine higher with a Stiletto, because they hang on better than most props when raised up on a jack plate.
Sal
Kevchap posted 09-17-2007 08:58 AM ET (US)
MY 1992 Johnson 150 is rated at 5000 rpm. I lifted up 1" more to 2.5" above keel. The 19 turns 5200 trimmed out at 46 mph with 50 gals of gas. It does not hold well that high, vents in turns and heavy chop, so a stiletto may be the answer but I'm still thinking a 19" is the right prop.
Sal DiMercurio posted 09-17-2007 09:54 AM ET (US)
Kev, you 150 's maximum rated rpms are 5500,......5000 to 5500,....always go to the highest number & your engine will be happy.
5000 rpms is to low, because if you put anymore weight in the boat, your rpms have no place to go, but down, & than your over propped & killing your engine, by whats called "Lugging".
Prop her for 5500
Sal
Kevchap posted 09-17-2007 04:30 PM ET (US)
Sal, It's probably a difference in opinion but this is what I'm reacting to.
Per OMC factory service manuel. Operating range is 4500-5500 and 150 hp rated at 5000. I like to run around 5200 WOT so if I add weight I'm still in the middle of my operating range. Dropping to a 17" would get me to 5500 but also drop my 4000 rpm cruise speed accordingly which means reduced MPG.
Any engine dyno report I've seen shows a drop in power as you raise engine RPM above design rpm. Besides it's a Whaler, I'm not winning any races anyway. I do appreciate a good debate though.
I'm going to do some research on Stiletto props, I do need something that will hold better in turns at this engine height.
Sal DiMercurio posted 09-17-2007 10:38 PM ET (US)
By propping that engine so it can reach it's factory maximum rpm of 5500, your allowing the engine to put out "LESS" effort at 4000 rpms [ cruise ] than if you prop it to only reach 5000 rpms.
You will certaionly "not" hurt it, by allowing it to reach 5500 rpms, in fact, your engine will be happier it is able to breath a bit easier, than if you put a 500 rpm load on her.
It's a small load , but it's still a load you don't want.
Rule of thumb is, prop for factory recommended maximum rpms, while trimmed out & normal load.
I don't know who you have been talking with, to get in your head, to prop your engine 500 under maximum, but your going to find propping for maximum rpms is going to give you the best performance, "AND" fuel economy.
If you start out 500 rpms under maximum rating, adding any load at all, is going to bring it lower yet.
5000 rpms is safe, but 5500 is allowing the engine to turn your cruise rpms [ 4000 ] with less effort, than if only allowed 5000 max.
Sal.


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Author	Topic: Using transom "wedges" on an 18 Outrage with jack plate
ewalsh	posted 09-12-2007 07:27 PM ET (US) Hi gang, The SlideMaster brand 6" jack plate I just got came with a set of alluminum "wedges" that I was told effectively shim the jack plate off the transom. My boat is a classic Outrage 18 with a 150hp Johnson 2 stroke. I have 3 questions. - What do they do for the boat's operating performance? - How are they installed between the transom and jack plate? - Should they be used with my application? Thanks a lot! Ed
Sal DiMercurio	posted 09-12-2007 10:45 PM ET (US) You don't need them with your boat. Those wedges are for transoms that have far more deadrise than yours, & the wedges are inserted between the jack plate & the transom to push the bottom of the plate out, away from the boat, otherwise you would have to run your engine at about 2/3 - 3/4 trim out just to keep the boat level. Without the wedges on another type of boat, the boat would ride to flat, with little chance of even trimming up enough to get the boat to porpoise, because the lower unit would darn near be right under the transom. Again, they "aren't" for your application. Sal
Kevchap	posted 09-13-2007 09:12 AM ET (US) I have the exact boat, motor and jackplate you do. I installed my jackplate without the wedges and it works wonderful. I agree with Sal. As I stated before my rig has the cav plate 1.5 inches above the keel. This set up works well with a generic alum prop for all around driveabilty, although I'm sure it's not the fastest set up possible. I'm planning on experimenting with raising the motor this weekend and I'm still shopping for the "perfect" prop. My goal is 50 Mph WOT and 40 MPh at 4000. I'm presently at 47 MPH WOT [light load]and 36 Mph at 4000 so this goal is lofty.
ewalsh	posted 09-14-2007 01:39 PM ET (US) Sal - thanks you for your advice. I'll take it! Kevchap - thanks as well. What prop are you currently running? Thanks, Ed
Kevchap	posted 09-14-2007 04:56 PM ET (US) Michigan 14.5 x 19 Alum. It's just to get me going and will become a spare. I'm in search of a good SS prop. I believe 19" is the right pitch for this engine, 17" turns to many rpm's and is hard on mpg.
Sal DiMercurio	posted 09-14-2007 10:24 PM ET (US) That engine needs to reach 5500 rpms @ wot. My thoughts are a 17p omc s/s. Or try a 14.25 x 15 or 17P Stiletto. You will be able to raise the engine higher with a Stiletto, because they hang on better than most props when raised up on a jack plate. Sal
Kevchap	posted 09-17-2007 08:58 AM ET (US) MY 1992 Johnson 150 is rated at 5000 rpm. I lifted up 1" more to 2.5" above keel. The 19 turns 5200 trimmed out at 46 mph with 50 gals of gas. It does not hold well that high, vents in turns and heavy chop, so a stiletto may be the answer but I'm still thinking a 19" is the right prop.
Sal DiMercurio	posted 09-17-2007 09:54 AM ET (US) Kev, you 150 's maximum rated rpms are 5500,......5000 to 5500,....always go to the highest number & your engine will be happy. 5000 rpms is to low, because if you put anymore weight in the boat, your rpms have no place to go, but down, & than your over propped & killing your engine, by whats called "Lugging". Prop her for 5500 Sal
Kevchap	posted 09-17-2007 04:30 PM ET (US) Sal, It's probably a difference in opinion but this is what I'm reacting to. Per OMC factory service manuel. Operating range is 4500-5500 and 150 hp rated at 5000. I like to run around 5200 WOT so if I add weight I'm still in the middle of my operating range. Dropping to a 17" would get me to 5500 but also drop my 4000 rpm cruise speed accordingly which means reduced MPG. Any engine dyno report I've seen shows a drop in power as you raise engine RPM above design rpm. Besides it's a Whaler, I'm not winning any races anyway. I do appreciate a good debate though. I'm going to do some research on Stiletto props, I do need something that will hold better in turns at this engine height.
Sal DiMercurio	posted 09-17-2007 10:38 PM ET (US) By propping that engine so it can reach it's factory maximum rpm of 5500, your allowing the engine to put out "LESS" effort at 4000 rpms [ cruise ] than if you prop it to only reach 5000 rpms. You will certaionly "not" hurt it, by allowing it to reach 5500 rpms, in fact, your engine will be happier it is able to breath a bit easier, than if you put a 500 rpm load on her. It's a small load , but it's still a load you don't want. Rule of thumb is, prop for factory recommended maximum rpms, while trimmed out & normal load. I don't know who you have been talking with, to get in your head, to prop your engine 500 under maximum, but your going to find propping for maximum rpms is going to give you the best performance, "AND" fuel economy. If you start out 500 rpms under maximum rating, adding any load at all, is going to bring it lower yet. 5000 rpms is safe, but 5500 is allowing the engine to turn your cruise rpms [ 4000 ] with less effort, than if only allowed 5000 max. Sal.