RXP 155 Upgrade Rccomendations

[bumblebeerxp07]

Hello to all, new guy here. A little background, I'm an aircraft mechanic and have been turning wrenches my entire life but have limited small engine experience and almost zero PWC experience. I'm currently contracting in Afghanistan and bought a 2007 RXP 155 while I was home on vacation last month. I absolutely love it. I will be coming home permanently next month and, while I'm already satisfied with the boat, I wouldn't mind making a few tweaks to get a little extra performance.
At first I considered ECU upgrades, but man are they expensive. Not to mention I'm not sure how much extra they will give me with the NA engine. I know they work better on boosted motors but unless I really can get 30-40hp out of it, I'm not paying $900-$1300 for a moderate improvement. Also, I do want the engine to last with as few problems as possible, which is one of the reasons I went with the 155 vs. the 215.
Right now I get about 58 on the speedo (probably more like 55 if I GPS it). I Would like to hit the 60 mph mark regularly with as few mods as possible. This is where I need help. From perusing the forum here, I get the impression that a good starting point would be an intake grate. Thinking about the Top Loader. Also I'm considering a wedge, however I am worried that it may make it more likely to porpoise. It already starts to do so when the tank gets low, and I don't want to make it any worse than it already is. Any comments on this?
Other than that, I'm looking for any other ideas or comments on different upgrades (i.e. what is really worth doing). Like I said, I'm basically a blank slate here as far as knowledge on improving performance on these things, so any help will be appreciated. Money isn't really an obstacle as long as I'm getting what I pay for. And again, I'm not looking to turn this thing into a race machine, so anything that would significantly compromise engine durability is out. Just looking for a little extra top end or even some improved acceleration. Grate, wedge, impeller, engine upgrades? I'm completely open to suggestions and input. Thanks in advance for the help.

 

[KK40384]

Improving the performance of a 155 is going to be hard to do. The cost vs gain ratio is going to be way off. With a 155 you're pretty much limited to an air intake and free flow exhaust. That may gain you a couple rpm on top end but not enough to spin an impeller with more pitch. Upgrading the impeller may improve your holeshots slightly but will cost you too speed. Intake grate will add drag, while improving handling and cavitation in choppy water, the 155 just doesn't make the power to overcome that drag on the high end.

In other words you are pretty much stuck where you're at. Throwing some money at it you may gain 1-2 mph but that's about it. Your best bet if you want more performance is to sell it and buy a supercharged ski.

 

[Coastiejoe]

I have to agree with the above post.

It is like you want a 215 or better engine but don't want the potential risks or costs that can come with them.

Impeller and grate will help out to a pretty large degree for the out of the hole application but will almost always cost you top end speed.

You can get an impeller that will increase your top end but will cost you out of the hole performance. And even at that, the engine will work harder as it is under a heavier load.

The top loader grate may help over all if it is choppy water. Smooth water it will act as a drag and with your engine you can't over come that.

A 4 inch cold air intake will help for sure but maybe only 1 or 2 MPH.

You could get the module that removes the rev limiter and gain a bit of top end. Not sure it is worth the additional abuse that the engine will take though.

Do you have VTS on that ski?

I have the 255 Super Charged engine in my RXT-X and it is amazing. Yes, i will have to do a SC rebuild around 100 hours. But that is the cost of have fun,,,,

I also own a GTX with the 155 engine. Like you said, great engine for what it is. My daughter hits 59 MPH on smooth water (she weighs about 135 ish).

 

[bumblebeerxp07]

Well, not what I wanted to hear, but I guess I was kind of expecting it. I do ride the majority of the time in chop, so the grate might be what I want just for the extra acceleration. But I don't want it to cost me too much top end. I was hoping there would be some tricks to bump it up a bit, I would be thrilled with consistently hitting 60. I've hit 60 on the speedo a few times but it stays consistently at 57-58 with me on it on flat water and I weigh about 220. I've also read about filling in the bolt holes on the ride plate. I figure maybe doing that will make up for the extra drag of the top loader and then I could just be happy with the same top speed, but better handling and hole shot. Does that make any sense?

I really don't want to deal with the SC. I think I will get the intake and exhaust upgraded though just for fun. I am happy with it for what it is, but I'm a tinkerer and this is a whole new world to me. It is almost a non option for me to just leave everything stock because it will drive me nuts thinking about the few little things I could do to improve it just a fraction :facepalm: . It's a sickness I guess lol. So from what I'm hearing, I think I'll go: intake, exhaust and if it makes sense to you guys, top loader and fill in the ride plate.

I don't have VTS. So does that mean the wedge might help a bit, or no?

 

[KK40384]

Intake exhaust fill ride plate holes intake grate opas delete and a wedge would probably get you close to 60. It would definitely get you there if you were a smaller guy but that's not always an easy mod lol. I think you'll like the exhaust. It sounds wicked. There's a thread with a video in this section on how to make a free flow exhaust yourself by yours truly. It'll save you some $ since you're handy with some tools.

 

[bumblebeerxp07]

Sounds like a game plan. I assume opas delete is just increasing or removing the rev limiter from the ECU. How do I do that for a decent price? Like I said, I'm not stingy with the money, but no way am I buying any of those $900 software programmers just to get an mph or two. Just not worth it. Btw kk, I love that ski you got there. That color scheme was by far the best from that era imo. I really wanted to buy an RXP like that but they either didn't make them, or I just couldn't find one in viper red that wasn't supercharged. Anyway, thanks again for the advice.

 

[KK40384]

No the opas delete, or better known as opas block off kit, removes the two paddles located at the rear of the hull and replaces it with just some block off plates. It reduces drag at high speeds and can allow for a little more mph on top. Not sure how much it would help at 57-60 but I know at 67-70 it does help.

 

[KK40384]

Here's a link:

http://www.rivayamaha.com/RivaStore/product_page.asp?Category=O.P.A.S. Performance Block-off Kit

 

[bumblebeerxp07]

Well, if I notice any improvement with these mods, I'll be happy. Especially since it looks like I can do all of that for a few hundred bucks. Not much risk there. So thanks for the help and I'll let you guys know how it turns out when I get home in a couple months.

 

[Doohounde]

60 is reachable. I have a modded RXT, and two GTi 155s (08 155 and 2011 Limited). A buddy and I did similar mods on his RXP 155 and one of my GTis. We did 4 inch cold air, prop repitch (new solas for me), rev limiter (remap), exhaust, OPAS lock to up on his, ride plate fill and smooth. We did some small things to help and hit craigslist for some parts and tried to do these things as reasonable as possible. Good results. In the big group that we ride with here in NW Florida, if we all line up and go for it, his RXP and my GTi will walk away from any other 155 from start to top end. Nothing drastic, but steady pull all the way. I love my RXT but like carving on his RXP and tossing my GTi around. You can ride the 155s like you stole em in any conditions with no supercharger worries or massive amounts of gas guzzling.

 

[Doohounde]

KK, I see that you have an RXT. Any mods. I have been tweaking/tuning my 07 for a few years now. New tweaked supercharger, solas impeller, pump wedge, air intake, grate, OPAS, and a couple of other small things. I had a supercharger bearing failure (not clutch) several months ago. I had the stock charger rebuilt @ 50 hours and it had bearing failure at 110 hours. The wheel touched down and ground itself up quite a bit. The motor was salvageable. Flush, oil pumps rebuilt, PTO, some other stuff while it was apart. It's now back together and running well (just over 70 GPS, strong acceleration). How do you like your ski? I am originally from Michigan (KZOO) but retired from the Air Force here in Fort Walton Beach Florida. The riding here is fantastic. How do you like your RXT?

 

[KK40384]

I like it! I regret not buying the RXT-X because I didnt like the orange/silver, but other than that no regrets. I have pretty much the same mods as the ones you have except SC. Mine is completely stock SC rebuilt about 30 HRS ago. Mine came with the ceramic washers which failed at 27hrs and took out everything. Dealer warrantied everything and upgraded to steel washers. I have since rebuilt the SC once more with the new upgraded shaft and everything. I'm looking at adding a ET127 wheel and 42lb injectors to crack 70 on gps. I'm sitting pretty at 69.7 on gps.

 

[red2blue]

.... while I'm already satisfied with the boat, I wouldn't mind making a few tweaks to get a little extra performance. .....bllsheet...if you were satisfied you wouldn't be looking for more....
... Also, I do want the engine to last with as few problems as possible, which is one of the reasons I went with the 155 vs. the 215.
Just looking for a little extra top end or even some improved acceleration. Grate, wedge, impeller, engine upgrades?...for the 155?...wouldn't even bother... I'm completely open to suggestions and input. Thanks in advance for the help.

sell it and get a 215...or better.