What should the max rpm be on 16 24' boats?

[WickedPorter]

How can you tell if it is a CARB model?

You will see this sticker on the side of the boat and near the engines:



Mine is opposite of most ... I can get up to ~7400RPM on starboard, around 7250 on port. Top speed with half tank and just me is around 50-51mph.

 

[haknslash]

There is also this thread which goes a little in-depth about the stickers and CARB/SULE boats https://jetboaters.net/threads/less-than-7300-rpms-2015-ar240.5631/

 

[Jeffrey]

I picked up a 2016 Limited S E-Series a few weeks ago. It was used as a sales demo (got a pretty good deal on it) with 13 hours at delivery. I'm seeing the max RPM of around 7400 on both engines. The net effect is 46-48 mph max depending on load. It's a non-CARB model (132kw/177HP). Does anyone know if the E-series boats have a throttle adjustment like the non-e-series do? There doesn't seem to be a service manual available yet.

 

[Mainah]

It seems to me that the engine compartment lacks a way to get enough fresh air in with how well they are sealed up now. I wonder if flipping the blowers over and turning them on would be enough to get the engines to perform better? Obviously only for a short duration test and I can't say that I would try it myself but just a thought to see if the engines are fresh air starved (more o2 in fresh air).

 

[swatski]

It seems to me that the engine compartment lacks a way to get enough fresh air in with how well they are sealed up now. I wonder if flipping the blowers over and turning them on would be enough to get the engines to perform better? Obviously only for a short duration test and I can't say that I would try it myself but just a thought to see if the engines are fresh air starved (more o2 in fresh air).

I was wondering the exact same thing when I brought her home tonight and looked, trying to figure out what happened to the fresh air vents/cut outs at the back of the engine bay (as in previous MY). They are gone...! There are no vents!
It's not even the enclosed space, as the lack of openings/vents that worries me.

I couldn't figure where the blower was venting either...

This is definitely something that needs to be addressed, fresh air supply.

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[Kane]

I picked up a 2016 Limited S E-Series a few weeks ago. It was used as a sales demo (got a pretty good deal on it) with 13 hours at delivery. I'm seeing the max RPM of around 7400 on both engines. The net effect is 46-48 mph max depending on load. It's a non-CARB model (132kw/177HP). Does anyone know if the E-series boats have a throttle adjustment like the non-e-series do? There doesn't seem to be a service manual available yet.

I don't believe there is anyway to adjust your throttles with the Eseries or X series. Everything is drive by wire so hopefully we will see someone offer a programmer that give more power!! As for your rpms, it seems like most of us are between 7400-7600 depending on passengers, fuel, coolers full of beer etc.

 

[Julian]

I've not studied the air venting on the boat...but not had any issues with starvation that I'm aware of....so not sure there is a problem there. No need to turn the blowers around....assuming there is venting....it would work with the blowers going either direction.

Regarding electronic throttles, again I've not studied them, but I have to assume there are 2 servos, one on each engine, that attach to the throttles. This used to be via a typical wire connection....but perhaps they've direct connected them now?

 

[Mainah]

My assumption on the throttles is that they potentiometers that send signals directly to the ECU and the ecu in turn interfaces with the throttle bodies which have built in servos. In the non e/x boats the throttle cables pull the APS/TPS (a dual potentiometer) which in turn sends signals to the eco and throttle body. The only reason for adjustment on the non e/x boats is the cables.

@Julian I get that the blowers will naturally suck air into the compartment from the lower openings as they blow air out. I just don't think there is much fresh air available to be sucked in from a volume perspective once you consider how much volume the engines are using in that relatively tight and nearly sealed engine compartment. Perhaps I will stick my tube inflator in the fire port and turn it on while at wot to see if it makes a difference.

 

[swatski]

Finally did some speed runs last week, showing pretty much the same as most here reported.
I get about 49mph with full tank and 5-6 in the boat, seems to be the norm.
1/2 tank, just myself, topping at 51-52mph. The port side RPM spins at 7600+ at WOT, consistently higher than strbd by about 100-150 RPM. No mods. Yet.


Interestingly, the port side impeller, but not starboard, will momentarily spin over 8,000 RPM when pushed hard from a stop; that does NOT register on a digital Connext tach (the screen), but I can hear it and see it on the analog gauge. It is very brief and generally not easily detectable and not an issue, but it IS there. (I like to know all the symptom'ology)

That minimal (so far) port slippage would be easy to remedy with Lucky 13 cone. Which would also bring the RPM down by about 200 making the port almost equal with the starboard (at WOT). From there, I could just do some impeller tweaking to get within 100-150 RPM of the rev limiter, after any air intake mods.

Boat is dynamite with no mods though, very satisfying.

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[subysti]

Just an FYI the blowers vent out under the rear facing seat backs on the stern.

 

[swatski]

Just an FYI the blowers vent out under the rear facing seat backs on the stern.

Right, but there is no extra openings in the stern to allow airflow? I can't figure out how does fresh air get in if the blower is off, other than through gaps.

Good thing is, it doesn't seem to hurt much.

I keep forgetting to test if air is sucking in through the fire extinguisher hole at wide open throttle, which would suggest vacuum and air starvation inside.

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[Bryan L]

51 mph and 7600 rpm would be a pipe dream. Jealous. I'm celebrating if I achieve 44mph and 6600 rpm. I figured that air would have been pulled in from the blower ducting.

 

[Mainah]

@swatski- I tested wot with the engine hatch held ajar. No difference in rpms so not air starved stock. Depending on how tight you make things with your sound proofing that could become a factor though.

@Bryan L - I can see your point in theblower ducting when the blowers are off but what about when they are running? Must say I am not sure where the air is all coming in from but it is getting in there. Those numbers seem just a tad low even for a carb boat. Have you tried the throttle adjustment? When was the last time the hull was cleaned? Have you ever sucked something into the impellers? Ever driven the boat with just you in it?

 

[Dough]

Bryan is at 4200 feet.

 

[Mainah]

Ahh. That makes since. Throttle body spacers and elevation pitched impellers may help.

 

[Bryan L]

@Bryan L - I can see your point in theblower ducting when the blowers are off but what about when they are running? Must say I am not sure where the air is all coming in from but it is getting in there. Those numbers seem just a tad low even for a carb boat. Have you tried the throttle adjustment? When was the last time the hull was cleaned? Have you ever sucked something into the impellers? Ever driven the boat with just you in it?

It never crossed my mind that the engine bay could be so airtight that restricted air flow would be a problem, especially with all the wires, cables and tubing running in and out of it. Now if we can come up with a way to force feed cool air right into the throttle bodies.

BTW-I really appreciate what you bring to the forum. The time you took to look into the Connext voltage reading issue was straight up awesomeness!! No stone left unturned!

Bryan is at 4200 feet.

You are correct, @Dough! The house sits around 4200 and we usually trailer the boat to either Pineview Res. (~5000) or Bear Lake (~6000). I hope to get a chance to take the boat back east and open her up, just so I can cackle like I just robbed an 1800's Wells Fargo stagecoach. In the meantime, I'll remain jealous of those who can hit the 7500rpm/50mph range and live at sea level!

Throttle body spacers and elevation pitched impellers may help.

@sysinu has been a huge help in this regard. He lives and boats at an even higher elevation, so he's been there and done that. The throttle body spacers just arrived today and I will be repitching the impellers in the spring. I'm actually expecting a small increase in top end, acceleration and fuel economy. I will try anything to help this boat breathe better and turn those screws as efficiently as possible.

 

[swatski]

@swatski- I tested wot with the engine hatch held ajar. No difference in rpms so not air starved stock. Depending on how tight you make things with your sound proofing that could become a factor though.

Tested that today, seems to be no problem with extra soundproofing. The weather was cool and dry which helps but at least I can rule out any serious air starvation.
(That was a bit of a concern of mine having sealed the engine hatch really well (post #19): https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/ ).

So the boat ran around 50 mph all day long (53-55 mph going down and 48-51 mph going up the river at WOT), w/two up and 3/4 tank of fuel. Hitting the rev limiter (at 7800+ rpm) on both engines, definitely also have some cavitation on take off.
Ribbon and snorkel delete only, so far. Next project -- adding the L13s, I think?

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[Mainah]

@swatski - When you did the ribbon delete did you throw in those riva rings or just straight delete?

 

[swatski]

@swatski - When you did the ribbon delete did you throw in those riva rings or just straight delete?

yes I did use the RIVA rings/spacers this time. I seriously doubt those are critical, but figured might as well at $40 a piece. And I was able to append those to my SeaDek order (to avoid scrutiny).

 

[Mainah]

I am not sure they are critical either. That said RIVA is great at squeezing every bit out of jet skis with mods so I guess they did that out of experience.

Just curious as I am considering doing as you did but really don't want to void my warranty or worse yet bypass the flame arresting safety nature.