PsychoXP18CC
Well-known member
Thought I'd post this since I don't see a lot of info out there on adding setback jackplates to mod-v style tins.
So I've been threatening to install a plate on my boat since I got it 3.5yrs ago, well I finally did it.
Reason to install it at all? To gain back some of the draft lost to the factory setup. My Yamaha F70 was installed on my Xpress XP18CC where the prop shaft was 9.75" below the bottom of the hull. The boat was propped reasonably well for that setup as I was able to hit the max rated rpm of 6,200 with just me a minimal gear in the boat, and trim up to run about 33mph before the boat porpoised.
I consulted a local shop who specializes in prop work and builds their own line of Jackplates. Steve's Custom Props/HydroDynamics. I am not affiliated in any way, just a customer who was referred to them.
Their advice was to put a 6" setback plate on the boat, so that's what I bought.
Installation wasn't too bad. Used a forklift at my shop/work to lift the OB off and reinstall. Four bolts off, clean up old silicone, four bolts and new silicone and the plate was on, four more bolts and the OB was hanging on the plate.
The downer was discovering the additional setback bound my steering cable up and made the steering extremely tight. Most side console rigs wouldn't suffer from this due to the angle of approach on the cable. Mine, being center console, comes up from a chase in the bilge and makes a tighter turn to the OB. So I ordered a cable 1' longer and four days later it arrived from amazon.
While I waited on the new cable I got my new water pressure gauge installed. Tapped into the tattle tell line at the block and used the new tube I pulled into the chase when i pulled the old steering cable out. When my new piece of 1/4" thick black phenolic material arrived I built the new gauge bezel for the dash, and cut the dash out more to accommodate the additional gauge.
So once all that was done, nothing is ever simple for me, I finally got to go out and do some testing.
Results with the plate set at 4" of prop height;
Alone with minimal gear in far less than ideal conditions. About a 25mph wind trying to stay close enough to shore to stay in slightly less than whitecapping water. Top speed improved to 36mph and hit the 6,500rpm rev limiter with ease. I could trim up to where the prop would blow out without any porpoising. A whole lot left on the table.
Next trip to the lake was just me, but with a full load of catfishing gear. Boat still ran 36mph max because it still hit the rev limiter but took a little more trimming up to get it to do so. Still a lot on the table.
This past weekend I spent three days fishing with more gear than I carry at any other time of year, and a buddy who goes 225lbs easy. Actual speed was more difficult to gauge because we were in a tighter river that winds and bends so I could never truly wring it out, plus we either had a down current or up current to deal with. I do know this now though, I can still hit the rev limiter, and the prop will blow out a little bit in extreme turns. Still no porpoising.
Net Result:
So far I've gained speed, the boat is much more responsive to steering input, the hull seems to ride higher/have more lift at any speed above barging, I gained almost 6" of draft, water pressure has yet to dip in any maneuver, and I feel there is more to be gained with either some prop work or new prop.
The only down side, if it even is one, is the boat now trailers a bit differently. Moving that 265lbs back 6" and raising it 6" makes the boat generally feel bigger while trailering. But no doubt I'll get used to it.
We will now be adding some cup to the prop and see how it likes that before a decision is made on a new prop. I need an extra prop anyway, so even if the modified prop works great I'll still be playing with a new one at some point.
Over all, I am very happy with the results, and will only be happier once we get the blowout under a little more control and tame the rpm a bit, hopefully gaining another mph or two in doing so. Just this weekend I saw a huge difference in the 6" draft gain. We were fishing a lot of sand bars and I noticed right away I wasn't having to trim up to keep the skeg from grounding.
I'll have to dig some pics out of my phone, but will post them when I do.
So I've been threatening to install a plate on my boat since I got it 3.5yrs ago, well I finally did it.
Reason to install it at all? To gain back some of the draft lost to the factory setup. My Yamaha F70 was installed on my Xpress XP18CC where the prop shaft was 9.75" below the bottom of the hull. The boat was propped reasonably well for that setup as I was able to hit the max rated rpm of 6,200 with just me a minimal gear in the boat, and trim up to run about 33mph before the boat porpoised.
I consulted a local shop who specializes in prop work and builds their own line of Jackplates. Steve's Custom Props/HydroDynamics. I am not affiliated in any way, just a customer who was referred to them.
Their advice was to put a 6" setback plate on the boat, so that's what I bought.
Installation wasn't too bad. Used a forklift at my shop/work to lift the OB off and reinstall. Four bolts off, clean up old silicone, four bolts and new silicone and the plate was on, four more bolts and the OB was hanging on the plate.
The downer was discovering the additional setback bound my steering cable up and made the steering extremely tight. Most side console rigs wouldn't suffer from this due to the angle of approach on the cable. Mine, being center console, comes up from a chase in the bilge and makes a tighter turn to the OB. So I ordered a cable 1' longer and four days later it arrived from amazon.
While I waited on the new cable I got my new water pressure gauge installed. Tapped into the tattle tell line at the block and used the new tube I pulled into the chase when i pulled the old steering cable out. When my new piece of 1/4" thick black phenolic material arrived I built the new gauge bezel for the dash, and cut the dash out more to accommodate the additional gauge.
So once all that was done, nothing is ever simple for me, I finally got to go out and do some testing.
Results with the plate set at 4" of prop height;
Alone with minimal gear in far less than ideal conditions. About a 25mph wind trying to stay close enough to shore to stay in slightly less than whitecapping water. Top speed improved to 36mph and hit the 6,500rpm rev limiter with ease. I could trim up to where the prop would blow out without any porpoising. A whole lot left on the table.
Next trip to the lake was just me, but with a full load of catfishing gear. Boat still ran 36mph max because it still hit the rev limiter but took a little more trimming up to get it to do so. Still a lot on the table.
This past weekend I spent three days fishing with more gear than I carry at any other time of year, and a buddy who goes 225lbs easy. Actual speed was more difficult to gauge because we were in a tighter river that winds and bends so I could never truly wring it out, plus we either had a down current or up current to deal with. I do know this now though, I can still hit the rev limiter, and the prop will blow out a little bit in extreme turns. Still no porpoising.
Net Result:
So far I've gained speed, the boat is much more responsive to steering input, the hull seems to ride higher/have more lift at any speed above barging, I gained almost 6" of draft, water pressure has yet to dip in any maneuver, and I feel there is more to be gained with either some prop work or new prop.
The only down side, if it even is one, is the boat now trailers a bit differently. Moving that 265lbs back 6" and raising it 6" makes the boat generally feel bigger while trailering. But no doubt I'll get used to it.
We will now be adding some cup to the prop and see how it likes that before a decision is made on a new prop. I need an extra prop anyway, so even if the modified prop works great I'll still be playing with a new one at some point.
Over all, I am very happy with the results, and will only be happier once we get the blowout under a little more control and tame the rpm a bit, hopefully gaining another mph or two in doing so. Just this weekend I saw a huge difference in the 6" draft gain. We were fishing a lot of sand bars and I noticed right away I wasn't having to trim up to keep the skeg from grounding.
I'll have to dig some pics out of my phone, but will post them when I do.
