Inconsistent MPH/Top Speed with 190

[SCSX190]

Just returned from a quick boat trip and couldn't exceed 34 top speed on a relatively calm, cool day with RPM hitting 7400-7600. All previous outings got me 40+ with 2 plus people? Checked clean out area for junk but found nothing? Boat hull just cleaned 2 weeks ago. What the hell is the deal with the variable speed on these jet Boats?

 

[mraz72]

did you check with gps?

 

[Matt J]

I feel your pain. Even though mine is a 192, last weekend we went out for a few hrs and my hr meter showed 2.8 hrs so I went full power for the first time to see what kind of speed/ rpm I could achieve. Boat had my wife and myself + 2 teenage kids. Top speed was 43 ish on speedometer, rpm was a little over 7k. From my research here guys are having issues with heat soak, etc on SC motors, so I know all about the variations these boats can have. I haven't checked my throttle cable slop yet, but going to look at it tomorrow when I get back home. I prob am going to join the ranks of pissed off owners if I can't achieve the published numbers from Yamaha.

 

[mraz72]

Matt, try going full speed when you just start out, prior to heat soak. You should be able to tell just by RPMs, 7800 = no heatsoak, ~7000 = heatsoak

the '17 models have a larger intercooler, that's what we all have to do to fix our issue,

 

[SCSX190]

I had the digital speedometer on display and it was the same as the gauge speedo. All previous runs were 40+ with a top speed of 42 a couple of weeks ago with much higher air temps and humidity. RPM also consistently hits 7400-7600.

 

[swatski]

Just returned from a quick boat trip and couldn't exceed 34 top speed on a relatively calm, cool day with RPM hitting 7400-7600. All previous outings got me 40+ with 2 plus people? Checked clean out area for junk but found nothing? Boat hull just cleaned last weekend. What the hell is the deal with the variable speed on these jet Boats?

That is weird. I would say at those RPM you should be going few mph faster.
Something is not right.

 

[Matt J]

Matt, try going full speed when you just start out, prior to heat soak. You should be able to tell just by RPMs, 7800 = no heatsoak, ~7000 = heatsoak

the '17 models have a larger intercooler, that's what we all have to do to fix our issue,

@Michael Rasmussen .. If I remember correctly, I went full power right outside no wake zone, just off trailer, so hard to believe it was heat soaked so quickly. OAT was 78 & water temp was 80 ish. Pretty piss poor really that these boats have such a Shitty IC !! If I would have researched the 192's more before my purshase, I never would have went with this model. Heck, my Tacoma has a aftermarket Magnuson SC/ rebadged and was sold as a TRD unit that off course has a IC as well. No issues with it on the 4.0 motor...except if you include the occasional slippage of clutch when I drive it like a raped ape.

 

[swatski]

I had the digital speedometer on display and it was the same as the gauge speedo. All previous runs were 40+ with a top speed of 42 a couple of weeks ago with much higher air temps. RPM also consistently hits 7400-7600.

I think humidity is as important as temps, if not more.
But you do get the RPM to go faster... So, that's not it.

 

[swatski]

Did you pass a rock or something through the pump that could have nibbled the prop? Doesn't have to be huge. I once ingested done rocks/ pebbles by getting to close to shore, the performance dropped immediately. I was still doing everything I did before, but the boat was just not the same.

 

[Matt J]

@SCSX190... That is weird. I guess the silver lining is your getting normal rpm's @ full throttle. In most cases it seems guys are not getting normal rpm's as well as slower top speeds. Curious, do the 190's have the same problems with achieving mid to high 7's rpm's like the 192's do?

 

[mraz72]

I know what mean Matt, I think we either deal with 5-10 mphs off or get a larger IC

 

[swatski]

@SCSX190... That is weird. I guess the silver lining is your getting normal rpm's @ full throttle. In most cases it seems guys are not getting normal rpm's as well as slower top speeds. Curious, do the 190's have the same problems with achieving mid to high 7's rpm's like the 192's do?

No heat soak in 1.8l n/a, and those are generally not very finicky. And ribbon delete can help a lot, too, worth about 200RPM on average in n/a.

 

[SCSX190]

I removed the clean out plug and felt the blades and they appeared to be fine. I have not beached the boat or run over any debris. It is in a wet slip so the hull could be dirty, or something built a nest in my jet pump? I just pulled the boat 2 weeks ago and cleaned/washed the hull but there was a disgusting ring around the waterline that I brushed off before going out today. There is an old boat in the slip next to mine that spews filth from the bilge on a daily basis. I guess I am pulling the boat out again to check the pump and hull. The boat is only 1 month old with 27 hours.

 

[swatski]

I removed the clean out plug and felt the blades and they appeared to be fine. I have not beached the boat or run over any debris. It is in a wet slip so the hull could be dirty, or something built a nest in my jet pump? I just pulled the boat 2 weeks ago and cleaned/washed the hull but there was a disgusting ring around the waterline that I brushed off before going out today. There is an old boat in the slip next to mine that spews filth from the bilge on a daily basis. I guess I am pulling the boat out again to check the pump and hull. The boat is only 1 month old with 27 hours.

I bet you that is it. Any hull growth/dirt/schmutz, even relatively minor, will hold you back A LOT.

 

[mraz72]

mine is wet slipped as well and the dirty hull kills speed. When you say wash the hull, what are you using? Getting that crap off takes acid.....

 

[SCSX190]

I use the car wash n wax that I use on my car and apply via a hull brush. The boat has been in the water since July 8th and pulled twice to clean and gas up. In the images below you can see the filth on the hull the first time I pulled the boat after 3 weeks in the water, and in my driveway after I cleaned her up. I guess I am going to purchase marine grade cleaner to see if that helps with the top speed.

When the boat had a filthy bottom it was still hitting 40+ with more people. The boat hit 40+ before and after the pics below.

 

[swatski]

Yep. Oxalic acid cleaners work best. Followed by some good cleaner wax to close the pores in gelcoat.

 

[SCSX190]

Old Crazy Horse here was good for about 40 MPH (and 3 feet out of the water) on every trip and I never had to close the pores in the gel coat. I guess I need to put her back in service for shits and giggles.

 

[SCSX190]

I pulled the boat today and the hull was covered in Lake Scum. I cleaned the hull with some toilet bowl cleaner, and car wash and wax with a hull brush. I wasn't able to open her up for long due to rough waters but I hit 38 real quick before I had to throttle down. I am rethinking the wet slip vs. dry storage. The hydro lift is 1500 a year extra.

 

[njmr2fan]

Try Collinite Fleet wax. So good on the boat, I started using this on my cars and the only thing that beats its longevity is CQuartz Sealant.

http://www.collinite.com/marine-wax/fleetwax-paste-wax/

http://www.collinite.com/marine-wax/liquid-fleetwax/