Lowe RX1860 Rambler Setup Suggestions

[Keith E.]

Good Morning,

I'm checking in to see what others are running and what their performance is with similar setups. Boat gets on plane quickly but porpoises with more than one second of trimming up. This happens with 1-3 people onboard. The only time that more trim could be used is with a 240lb passenger moving forward to the point of using the front deck for a backrest.

Per GPS, boat speed is 35mph with the tach showing ~5500rpm. The motor did turn 5800rpm, with more trim, when the aforementioned passenger moved forward. Boat speed went up 2-4mph.

For reference, my personal boating experience (20+ yrs ago) is with 14-16' jon boats, side console fishing boats, along with 20' Bullet & Allison bass boats. I've been around assorted others as well, just not the larger jon boats.

●Lowe RX1860,
Suzuki DF70A 4-Stroke Outboard (15 Spline) w/ OEM 3x13.875x15 Propeller

●Stern
•6g Fuel Tank
•One each 27 & 29 or 29 & 31 Lead Acid Batteries

●Port Locker
•~20lbs

●Minn Kota Terrova 12v 55# bow mount

●Bow Storage @
~65lbs

Please drop any questions, suggestions, etc.

TIA,
Keith

ETA: I'll work on getting pics of the engine/transom and maybe some pics or vids of the boat sitting and running.

 

[David Atkins]

Many things can cause your boat to porpoise, load distribution, engine trim, engine set back, no trim tabs; the list goes on. Being a flat bottom boat adds to your dilemma and porpoising issues, I would most certainly look for the most obvious, engine placement, set back and trim, that being said then maybe adding trim tabs might be a cost worthy addition; always- always check costs before making any changes as you don't want to spend money and not get a decent return. You can also look into transom pods as they may help with this issue. My boat has then and I have never had any porpoising issues, I also use a 6 inch hydralic jack plate which helps and also allows me to go into shallower water too! i have 1860 CC

 

[LDUBS]

My 18' boat (mod-V) has power trim. At WOT (and close to WOT) if I trim up just slightly too far it porpoises. Trim down just a tick and it goes away.

If it is like mine, the group 31 battery is pretty heavy. Assuming it is for the trolling motor, I wonder if moving it forward to the bow area might help.

 

[airshot]

Gotta experiment, no one can say for sure...all boats should be tested for weight placement to get best performance

 

[moedelawn]

As stated moving the batteries/weight forward is the best option and it helps plane quicker. If that isn't an option you can use fast steel or similar stick epoxy to make two round pieces to stick to the bottom at the transom. 1 1/2"-2" wide. Taper the front side. Put them in between the extrusions about halfway from the center to the edge. You can file them down or remove them if you don't want them. I've done this and my buddy who has a 16' Xpress with a F50 tiller had good results. Another friend who modifies and races outboards recommended that.

 

[David Atkins]

As stated moving the batteries/weight forward is the best option and it helps plane quicker. If that isn't an option you can use fast steel or similar stick epoxy to make two round pieces to stick to the bottom at the transom. 1 1/2"-2" wide. Taper the front side. Put them in between the extrusions about halfway from the center to the edge. You can file them down or remove them if you don't want them. I've done this and my buddy who has a 16' Xpress with a F50 tiller had good results. Another friend who modifies and races outboards recommended that.

Re: What does "Hook" in a hull mean?

The hook in the bottom of the boat if it is adjacent to the transom is probably built in by design. Its kinda like having a permanant trim tab installed. Its design is to help keep the bow down. If performance is what your looking for definately consider taking it out, thats one of a few things to do to help improve top speed (if your doing hull and paint work anyway). With the hook out, it takes less trim to lift the bow. Less trim means the prop stays in the water better, which will allow the motor to be run higher on the jackplate. All combined for more top end speed.

 

[moedelawn]

If he's porpoising with barely any trim then he won't want to take any hook out. You want the cavitation plate/ anti ventilation plate atleast to a neutral trim position. If it has to be negative trim to stop porpoising you are losing speed. That's why it gains speed with weight on the bow because of the increased trim.