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Author Topic:   Engine Height with Jackplate

Eggman posted 06-19-2009 04:46 PM ET (US)
Hello all, I have a 1983 V-20 with a 1983 175 Johnson Crossflow outboard. I just put a fresh powerhead on her and also purchase a Vance Manufacturing 6" setback Jackplate. I mounted the jackplate and then set the outboard on her mounted on the second hole from the top. At the highest available height for the jackplate, the antiventilation plate(the plate right above the prop) on the outboard is 3" higher than the lowest V at the bottom (stern)of the boat. Should I have mounted the outboard higher on the jackplate? Just to let everyone know I run an aluminum prop on her and do want a ss one but the wife will kill me if I spend another dime right now!!! Eggman
R T M posted 06-19-2009 08:58 PM ET (US)
I think your engine might be a little high, I have a 6" setback bracket on my 13 footer, powered by a 25hp 4 stroke. I run the cavitation plate 2" higher than the bottom. It seems to be the best position for me. Try out your boat and see where the cavitation plate is at wide open. Should be at top of water or a little above.
rich/Binkie
Sal DiMercurio posted 06-21-2009 11:39 AM ET (US)
The "V 20" has a tendancy to porpois even without a jack plate, & getting a plate that sets the engine back another 6" is going to really make you pull your hair out.
I own a "V20" & put a "Bob Machine shop" inter-changeable 2" or 5" setback on her.
The 5" won't allow you much trim on your engine, but after I changed the setting to the 2" setback, it really made a difference.
I fish quite aways off shore, so I have a kicker mounted on another permanet setting jack plate [ no adjustment ].
The extra 80 lbs from the kicker totally ruined the way the boat performed, so I installed Bennetts trim tabs [ M-20s ] & the tabs made my boat a beautiful performing machine.
If you are also going to run a kicker, keep in mind you can't mount the kicker right on the transom if you have the Bennett M20 tabs, because the tabs stick out about 10" & the lower unit on the kicker will hit them.
My main engine [ 200 hp DFI ] is 5" above the transom on the 2" setback.
When my boat is kept on the Sacramento river, I run the engine 5" above the transom, but when I fish the Pascific ocean, I lower the engine to approx 3.5" above the transom to avoid blowout in the sloppy waters of the ocean.
Keep in mind you only went half way in trying to up grade the performance of your boat, by putting a jack plate on, the other half is putting a stainless performance prop on that engine.
What you did is like putting a souped up engine in your car, but left mud & snow tires on it.
In order for you to improve the performance of your boat, you need to put the correct prop on your engine that's sitting up on that jack plate.
A s/s Stiletto 14.25 x 17 should allow that engine to spin up 5500 rpms, as the Stiletto 17 pitch is really closer to a 19 pitch in most other props.
The s/s Stiletto will completely change the way your boat performs, such as make it ride much higher on the water, & you wont believe your top end, or hole shot performance, compared to that aluminum prop.
When my boat is completely stripped down [ no anchor, one battery, no tools etc ] & just me & very little fuel, I can run my 21 pitch s/s Stiletto to 6000+ rpms, but under normal conditions with anchor, chain, 2 batteries, at least 30 gallons of fuel, 80 lb kicker & lots of 2 lb lead trolling salmon balls, I run a 19 pitch Stiletto & it allows me 5500 rpms on my DFI [ non carbed ] 200 hp Evinrude.
Do yourself a huge favore & throw that aluminum prop away, or just keep it for an emergency only prop.
Hope this helps you to get things right on your boat, because I think your going to borrow a s/s performance prop, & your going to agree with me.
Trust me, there's a reason why all bass boats & performance boats run stainless props, & probably most of those guys don't tell their wives they bought a decent prop for their rig.
The next time she buys a new purse or pair of shoes, get even.
Sal
Eggman posted 06-22-2009 09:52 AM ET (US)
Thanks Sal,
I was hoping you would chime in on this thread. I think I remember reading one of your posts and you said that the boat stopped porpoising when you had the 5" setback but when you added the kicker it ruined the ride and that's why you had to turn it over for the 2". I'll try to get a good used stiletto on e-bay for cheap. Thanks, Patrick
Tohsgib posted 06-22-2009 11:55 AM ET (US)
Only way to tell is to run it and see. Also get a waterpressure guage if going high.
Sal DiMercurio posted 06-22-2009 09:06 PM ET (US)
Nick is 100% right on the pressure guage.
Tom Clark can get you a good price on a S/S Stiletto.
When you get your Stiletto, run the engine at wot & slowly trim her out till she starts to slip [ watch your tach ], than trim her back in until she catches, than stop trimming, your gonna say,...."HOLY SH!!", this thing flys.
Do not run with your engine trimmed way in, as many people do, unless it's sloppy & you need to cut through the waves.
Concider Bennetts M20 tabs, you wont believe the difference.
With the tabs, you can get on plane & stay there around 2000 rpms.
If you shop around, you can get them [ tabs ] for about $400 .......on top of the $250 - $275 the Stiletto is gonna cost, [ or at least used to cost ].
That $700 will totally change the way your boat performs.
If you need to get ahold of me, my e-mail is.....Whaler1@sbcglobal.net
Sal
Eggman posted 06-22-2009 09:23 PM ET (US)
Thanks Sal, I'll work on the Stiletto first!!! Patrick
L H G posted 06-22-2009 11:02 PM ET (US)
Mercury's engine rigging manual, which I would think would be appropriate to any brand engine, recommends you go up 1/2" for every 6" of jackplate or transom bracket setback, as compared to where you originally would place the engine directly on the transom.
With an aluminum prop on that rig, you should be up 3/4" at most on the transom mount, then add another 1/2" for the setback.
If you get a performance prop like a Stiletto or other brands, use 1-1/2" on the transom, plus the 1/2" for the jackplate setback.
It's unlikely that any more running height than that would bring any increase in speed, and most likely hurt holding and trim ability.
I would recommend a Mercury Enertia or Vensura prop for your rig.
Tohsgib posted 06-23-2009 01:48 PM ET (US)
Sometimes it is not just speed Larry, 2" of draft means getting across the flats or pushing the boat 1/2 mile in 1' of water.
Eggman posted 06-25-2009 12:37 PM ET (US)
Hello all, Today I went out and tried her. I took a trip around the lake, opened her up @WOT and she held at straight ahead but slipped in the corners. dropped the jackplate down 1" and now she holds in the corners. Now the antiventilation plate is 2" above the lowest "V" at the bottom of the boat and when on plane it is above the water. I thought when I put the new powerhead on I would get more top end, "I did" but not as much as I hoped. Before the new powerhead I topped out @ 38 mph now I top out @ 41 mph. I have read others with the same setup have gotten between 48 and 50 mph. I think my problem is the prop. Right now I have an aluminum 14.5 x 19 on her but originally there was a 15 x 17. I bought the 14.5 x 19 because the other one was a little damaged and I use it as a spare in case I need to limp home. Do you think the higher pitched prop (19) is slowing me down? I still want a ss one and am looking. Patrick
Tohsgib posted 06-25-2009 12:47 PM ET (US)
Alum prop is your problem...what are your rpms? Your redline is 5500 and with a 19 or 21 SST you should be in upper 40's.
Sal DiMercurio posted 06-26-2009 10:57 AM ET (US)
I don't think that 175 with a 19p aluminum prop can twist 5500 rpms at wot.
Sounds like he's only getting around 4800 rpms.
Is your boat loaded with lots of weight like anchor & tools & 2 heavy batteries & 60 gallons of fuel?
Nick is right, that aluminum prop is like snow tires on an indy car.
If your going to do it,. do it right, not half way.
With a decent s/s prop, you can go up probably another 2" in height, & not blow out.
Sal
Tohsgib posted 06-26-2009 11:41 AM ET (US)
My 19 Revenge (1600lb hull) would go over redline with a 175 OMC and a 19 SST at about 52mph.
Eggman posted 07-17-2009 09:48 AM ET (US)
Ok, found a used perfect condition Stiletto 14 X 17 SS Prop for my boat and purchased it. I will put it on when I get it and let everyone know how it performs. Thanks to all who chimed in. Eggman
Sal DiMercurio posted 07-17-2009 11:04 AM ET (US)
Egg, your boat is going to be a completely different boat with your new prop, so be aware it's gonna handle way different,....better, but different from what you have become used to.
Your gonna love it.
Sal
jimh posted 07-17-2009 11:42 AM ET (US)
See
Engine Mounting Height
http://continuouswave.com/whaler/reference/engineMountingHeight.html
feles99 posted 10-26-2009 10:44 AM ET (US)
Hi Eggman, Please let me know how was the outcome after you changed the prop....
pancake55 posted 11-05-2010 01:15 PM ET (US)
just wanted to know how your prop jackplate combo went?

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Author	Topic: Engine Height with Jackplate
Eggman	posted 06-19-2009 04:46 PM ET (US) Hello all, I have a 1983 V-20 with a 1983 175 Johnson Crossflow outboard. I just put a fresh powerhead on her and also purchase a Vance Manufacturing 6" setback Jackplate. I mounted the jackplate and then set the outboard on her mounted on the second hole from the top. At the highest available height for the jackplate, the antiventilation plate(the plate right above the prop) on the outboard is 3" higher than the lowest V at the bottom (stern)of the boat. Should I have mounted the outboard higher on the jackplate? Just to let everyone know I run an aluminum prop on her and do want a ss one but the wife will kill me if I spend another dime right now!!! Eggman
R T M	posted 06-19-2009 08:58 PM ET (US) I think your engine might be a little high, I have a 6" setback bracket on my 13 footer, powered by a 25hp 4 stroke. I run the cavitation plate 2" higher than the bottom. It seems to be the best position for me. Try out your boat and see where the cavitation plate is at wide open. Should be at top of water or a little above. rich/Binkie
Sal DiMercurio	posted 06-21-2009 11:39 AM ET (US) The "V 20" has a tendancy to porpois even without a jack plate, & getting a plate that sets the engine back another 6" is going to really make you pull your hair out. I own a "V20" & put a "Bob Machine shop" inter-changeable 2" or 5" setback on her. The 5" won't allow you much trim on your engine, but after I changed the setting to the 2" setback, it really made a difference. I fish quite aways off shore, so I have a kicker mounted on another permanet setting jack plate [ no adjustment ]. The extra 80 lbs from the kicker totally ruined the way the boat performed, so I installed Bennetts trim tabs [ M-20s ] & the tabs made my boat a beautiful performing machine. If you are also going to run a kicker, keep in mind you can't mount the kicker right on the transom if you have the Bennett M20 tabs, because the tabs stick out about 10" & the lower unit on the kicker will hit them. My main engine [ 200 hp DFI ] is 5" above the transom on the 2" setback. When my boat is kept on the Sacramento river, I run the engine 5" above the transom, but when I fish the Pascific ocean, I lower the engine to approx 3.5" above the transom to avoid blowout in the sloppy waters of the ocean. Keep in mind you only went half way in trying to up grade the performance of your boat, by putting a jack plate on, the other half is putting a stainless performance prop on that engine. What you did is like putting a souped up engine in your car, but left mud & snow tires on it. In order for you to improve the performance of your boat, you need to put the correct prop on your engine that's sitting up on that jack plate. A s/s Stiletto 14.25 x 17 should allow that engine to spin up 5500 rpms, as the Stiletto 17 pitch is really closer to a 19 pitch in most other props. The s/s Stiletto will completely change the way your boat performs, such as make it ride much higher on the water, & you wont believe your top end, or hole shot performance, compared to that aluminum prop. When my boat is completely stripped down [ no anchor, one battery, no tools etc ] & just me & very little fuel, I can run my 21 pitch s/s Stiletto to 6000+ rpms, but under normal conditions with anchor, chain, 2 batteries, at least 30 gallons of fuel, 80 lb kicker & lots of 2 lb lead trolling salmon balls, I run a 19 pitch Stiletto & it allows me 5500 rpms on my DFI [ non carbed ] 200 hp Evinrude. Do yourself a huge favore & throw that aluminum prop away, or just keep it for an emergency only prop. Hope this helps you to get things right on your boat, because I think your going to borrow a s/s performance prop, & your going to agree with me. Trust me, there's a reason why all bass boats & performance boats run stainless props, & probably most of those guys don't tell their wives they bought a decent prop for their rig. The next time she buys a new purse or pair of shoes, get even. Sal
Eggman	posted 06-22-2009 09:52 AM ET (US) Thanks Sal, I was hoping you would chime in on this thread. I think I remember reading one of your posts and you said that the boat stopped porpoising when you had the 5" setback but when you added the kicker it ruined the ride and that's why you had to turn it over for the 2". I'll try to get a good used stiletto on e-bay for cheap. Thanks, Patrick
Tohsgib	posted 06-22-2009 11:55 AM ET (US) Only way to tell is to run it and see. Also get a waterpressure guage if going high.
Sal DiMercurio	posted 06-22-2009 09:06 PM ET (US) Nick is 100% right on the pressure guage. Tom Clark can get you a good price on a S/S Stiletto. When you get your Stiletto, run the engine at wot & slowly trim her out till she starts to slip [ watch your tach ], than trim her back in until she catches, than stop trimming, your gonna say,...."HOLY SH!!", this thing flys. Do not run with your engine trimmed way in, as many people do, unless it's sloppy & you need to cut through the waves. Concider Bennetts M20 tabs, you wont believe the difference. With the tabs, you can get on plane & stay there around 2000 rpms. If you shop around, you can get them [ tabs ] for about $400 .......on top of the $250 - $275 the Stiletto is gonna cost, [ or at least used to cost ]. That $700 will totally change the way your boat performs. If you need to get ahold of me, my e-mail is.....Whaler1@sbcglobal.net Sal
Eggman	posted 06-22-2009 09:23 PM ET (US) Thanks Sal, I'll work on the Stiletto first!!! Patrick
L H G	posted 06-22-2009 11:02 PM ET (US) Mercury's engine rigging manual, which I would think would be appropriate to any brand engine, recommends you go up 1/2" for every 6" of jackplate or transom bracket setback, as compared to where you originally would place the engine directly on the transom. With an aluminum prop on that rig, you should be up 3/4" at most on the transom mount, then add another 1/2" for the setback. If you get a performance prop like a Stiletto or other brands, use 1-1/2" on the transom, plus the 1/2" for the jackplate setback. It's unlikely that any more running height than that would bring any increase in speed, and most likely hurt holding and trim ability. I would recommend a Mercury Enertia or Vensura prop for your rig.
Tohsgib	posted 06-23-2009 01:48 PM ET (US) Sometimes it is not just speed Larry, 2" of draft means getting across the flats or pushing the boat 1/2 mile in 1' of water.
Eggman	posted 06-25-2009 12:37 PM ET (US) Hello all, Today I went out and tried her. I took a trip around the lake, opened her up @WOT and she held at straight ahead but slipped in the corners. dropped the jackplate down 1" and now she holds in the corners. Now the antiventilation plate is 2" above the lowest "V" at the bottom of the boat and when on plane it is above the water. I thought when I put the new powerhead on I would get more top end, "I did" but not as much as I hoped. Before the new powerhead I topped out @ 38 mph now I top out @ 41 mph. I have read others with the same setup have gotten between 48 and 50 mph. I think my problem is the prop. Right now I have an aluminum 14.5 x 19 on her but originally there was a 15 x 17. I bought the 14.5 x 19 because the other one was a little damaged and I use it as a spare in case I need to limp home. Do you think the higher pitched prop (19) is slowing me down? I still want a ss one and am looking. Patrick
Tohsgib	posted 06-25-2009 12:47 PM ET (US) Alum prop is your problem...what are your rpms? Your redline is 5500 and with a 19 or 21 SST you should be in upper 40's.
Sal DiMercurio	posted 06-26-2009 10:57 AM ET (US) I don't think that 175 with a 19p aluminum prop can twist 5500 rpms at wot. Sounds like he's only getting around 4800 rpms. Is your boat loaded with lots of weight like anchor & tools & 2 heavy batteries & 60 gallons of fuel? Nick is right, that aluminum prop is like snow tires on an indy car. If your going to do it,. do it right, not half way. With a decent s/s prop, you can go up probably another 2" in height, & not blow out. Sal
Tohsgib	posted 06-26-2009 11:41 AM ET (US) My 19 Revenge (1600lb hull) would go over redline with a 175 OMC and a 19 SST at about 52mph.
Eggman	posted 07-17-2009 09:48 AM ET (US) Ok, found a used perfect condition Stiletto 14 X 17 SS Prop for my boat and purchased it. I will put it on when I get it and let everyone know how it performs. Thanks to all who chimed in. Eggman
Sal DiMercurio	posted 07-17-2009 11:04 AM ET (US) Egg, your boat is going to be a completely different boat with your new prop, so be aware it's gonna handle way different,....better, but different from what you have become used to. Your gonna love it. Sal
jimh	posted 07-17-2009 11:42 AM ET (US) See Engine Mounting Height http://continuouswave.com/whaler/reference/engineMountingHeight.html
feles99	posted 10-26-2009 10:44 AM ET (US) Hi Eggman, Please let me know how was the outcome after you changed the prop....
pancake55	posted 11-05-2010 01:15 PM ET (US) just wanted to know how your prop jackplate combo went?