1997 700 LX Low Top Speed and HighTorque Steer

[Mack Garrett]

Hello Everyone, I have a 1997 700 LX DC with a 120 Force and a 3 blade 13X21 aluminum prop. When trimmed best speed is 43 MPH(GPS)with full fuel and 2 people on board. Is this a normal top speed for this model and HP or am I slow? Hole Shot is very good (1 to 1.5 seconds to on plane). Max speed RPMs are around 5050 with a recommended RPM range for this motor from 4750 to 5250). Also I have excessive torque steer when trimming when it first goes on plane but as I increase up trim it goes away. Also requires excessive down trim to stop porpoising in smooth water (I must trim down to the point that speed is effected considerably to prevent this from happening). Also at low to medium speeds it list or leans bad to the left with bad torque steer (pulling hard to the left). The only way to stop the lean and bad torque steer is to speed up and or slow down and trim. Keep in mind that when I am on plane it will trim level and all torque steer goes away. I have played with weight and balance and moved one of my 2 trolley motor batteries forward under the LH or passenger console (helped some) but adding more weight forward and or to the right side does not seem to help additionally. Motor could possibility be moved up one hole (the previous owner moved it up 3 holes from the lowest setting, said it didn't like it at all and then moved it down 2 holes, that is 1 hole higher that the lowest setting with the factory setting being in the lowest position. I know this does not sound good but it is not as bad as it sounds, I just feel that with the proper set up it could be much better. Any help in this matter would be greatly appreciated. Also is there a kit available to add a trim gage? Thanks Again Everyone. Mack

 

[TrepMan]

Hey Mack - Welcome to the board!





I have a very simliar boat/motor combo - '99 700lx DC Merc 115. My Merc has the same Max RPMs of 5250, My top end is 52-55 GPS depending on speed/load/conditions right at WOT 5200 RPMs. But i'm running a 13.75 x 25p 3 blade Turbo Stainless prop, holeshot is excellent lightly loaded and decent with my livewell full (which isn't often!! LOL). I can't help on motor height as I have a 4.5 inch manual Jackplate with mine. Normally I would say go down in pitch and you'd pick up 1-200 RPMS, but your top speed will decrease with a smaller diameter prop at this point. I haven't ran a aluminum prop, so I don't honestly know which way to go, my gut says get a 23-24P 3 blade SS prop and that should get you the low 50's from my experience.



on the trim guage, I took mine completely out and replaced it with a water pressure guage, I had never used or looked at the trim gauge while I had it, and the water pressure guage is key to me to not only tune the motor Height but also to watch to ensure it is always getting water pressure to cool the motor, just my 2 cents.



Good luck, hope this helped a little.



Trep

 

[mike daniels]

Yeah you're a little slow.



I have a nitro 175 sport (fish and ski) with a 90HP and a merc 12.5 x 23 pitch stainless prop. It will run in the mid 40s easy and will touch 50 in smooth water.



I'd start back at the factory settings and go from there. You cant really trust what the previous owner said.



What is the stock prop for your motor? That one sounds a little light



Probably something like I'm running would be more appropriate if you could spin it to 5200 RPM.



For Model boats, I reduced prop torqe by sharpening the prop. Don't know if it helps in real boats or not but it cant hurt to try.

 

[Mack Garrett]

Trep and Mike,

First of all I would like to thank the both of you for taking time to give me your thoughts on my problems, you guys suggestions really got me pointed me in the right direction. I went to the boat shop today and purchased a good condition used 22 pitch Quicksilver Turbo II stainless prop today (I wanted to try a 23P but its what he had that would work and was used and not new $$$). The difference it made was incredible. The excessive torque steer is gone, top speed increased to 49 MPH (GPS) with 2 people and full fuel and the purposing problems I had went away, all with only a 50 to 75 reduction in RPMs, it is like a completely different boat. I never had a clue that a propeller change could make such a difference and I still don't understand why it has changed all it did. Hole shot only suffered slightly adding I am going to say only a second or so to on plane. As far as the leaning to the left tendency goes it changed for the better but it still there. Before it would lean left at a slower speed range but could be overcome by increasing or decreasing speed a few miles per hour with a trim change, now the lean is not near as excessive but it it there for a much wider speed range but it is not even half as bad as it was. Anyway I am very pleased at the improvements from the prop change to say the least. Thanks Again you guys, I really appreciate your help. Mack

 

[TrepMan]

Mac - Glad we could help. If your RPMs only dropped a bit you could try raising the motor 1-2 holes, that may get you a little more RPMs and better holeshot. Glad you could get a good deal on a used prop. If you end up with some extra $$ also keep an eye on eBay, i've picked up a few good props reasonable over the years.