Throttle adjustment

[Bmeehan19]

Hey,
I’ve scoured this forum for a month now learning all I can from the countless threads on various topics. I picked up a new to me 2010 AR240 this year with 200 hrs on it. During the test ride it maxed at appx 7800+ rpm and hit 50 during cooler weather 65-70 degree ish At appx 100’ or less above sea level.

I brought it home. Changed the oil, let it a tad below the full line, new iridium plugs and lubed the intermediate bearings. Noticed my throttles weren’t going all the way to the stops.1/8” shy so I adjusted those using the cable attached to the POT.

I don’t normally go WOT but the kids love it and always ask for it. We were in upstate VT at appx 1200’ and it would only hit 46 @7400 rpm. Weird

Back home in CT and on the river try it again. Upstream with A tail wind hit 7500-7600 and 46mph quickly Then slowly to 50. Downstream against the wing was 75-7600 and 47-48.

I also noticed that the throttle at full forward just touches the stops. But on the water about 2/3 the way though the travel is max rpm the last 1/3 travel doesn’t produce more rpm or speed. So that means the throttle POT is not hitting the stop for the rpm and speed I’m currently getting.

Long story short, what did I mess up and how can I fix it.

Thank you
Bryan

 

[Bmeehan19]

Is my situation normal? Can anyone provide some insight?

 

[Dave burke]

I’m not sure I’m following your concern. You hit 50 at close to sea level initially and then you hit it again in CT at close to sea level. So doesn’t seem to me that you messed up.

Elevation and water temperature can have a significant impact. I don’t know if there are any formulas to determine how much, maybe others can help with this.

regarding your second to last paragraph, my boat does the same thing, ie the last bit of throttle travel doesn’t do anything. That’s been true for pretty much all the boats I’ve owned.

 

[Bmeehan19]

I don’t think I explained it completely. The initial test had about 400 more rpm and the throttles weren’t contacting the stops at wide open. After all the stuff I did. I lost 400ish rpm and the boat seems to top out (46mph)without the throttles hitting The stops. Is that common? Seems like there could be more if the throttle POT’s aren’t maxed out or I messed up the adjustment. And the 2nd time hitting 50 it took several minutes with a tail wind to get there. Very slow acceleration past 46 mph. Is that normal?

 

[Dave burke]

Mine gets to the mid 40s quickly and after that it’s slow to climb. Tops out at 48-50 depending on the conditions. I boat at about 1500 ft.

I haven’t adjustment my throttle linkages but intend to. As long as they’re right up against the stopper at full throttle, that me as you’ve done it right from everything I understand.

 

[Dave burke]

One other thought - how clean/smooth is the boat hull? That can have an impact as well.

 

[Babin Farms]

Last fall I could go 4-5mph faster than I can now. Colder air produces more HP. Water conditions, hull cleanliness, Air temp, weight in boat(fuel, toys, boards, racks, grill, tubes) play a big factor

 

[Bmeehan19]

Thank for the responses. The hull is clean and shiny. No paint fresh water trailered only. Usual ballast is 1-2 adults and 2 small children.

My buckets have some play in them and the boat tends to favor to the left. It does change with conditions but it seems they are a tad off. They do line up parallel to each other verified with a straight edge but the cables for the steering and the reverse bucket have some movement. Maybe they are fighting each other.

 

[tdonoughue]

@Babin Farms is right--there are lots of factors. If you were able to only get 40mph at WOT, I would be concerned. Shaving a few mph off usually is attributable to a few other factors. Humidity, temperature--things like that can affect rpm as well. So you have lots of factors at play.

I would leave it as is, enjoy it a bit, and collect a few data points. Sure, you may have something not-exactly-optimal. But before you go digging in, see if it does not resolve itself as conditions change.

 

[Joshua Miller]

I have the same year and model. Same issue with the slow climb to 50mph. I maxed out at 52 mph once with just me, my son, 1/2 tank and smooth water.

 

[BeauSko]

Did you happen to take note of the oil level before the oil change? I’ve read a lot of posts where, for these boats, the engines run optimally when oil level is about half way between the min n max line.

 

[BeauSko]

Also, did you ensure the gaps for the plugs were within spec?

 

[Bmeehan19]

Unfortunately I did not. Each motor is filled to 1 line below the F. I’ll try to find some info on the oil fill quantity tomseenif is have a bit to much in there.

Did you happen to take note of the oil level before the oil change? I’ve read a lot of posts where, for these boats, the engines run optimally when oil level is about half way between the min n max line.

 

[Bmeehan19]

That I also did not do. I thought those iridiums came sized and/or you shouldn’t touch them since the electrode is small. Did I get bad info there?

Also, did you ensure the gaps for the plugs were within spec?

 

[212s]

That I also did not do. I thought those iridiums came sized and/or you shouldn’t touch them since the electrode is small. Did I get bad info there?

The stock NGK plug LFR6A in the 1.8 N/A engines comes factory-gapped at 0.036 yet Yamaha spec calls for 0.031-35 - don't count on a plug being gapped for your needs out of the package. Iridium plugs for my vehicle are pre-gapped but specific to my engine and work properly, but Yamaha doesn't use iridium plugs so it's up to you to choose wisely.

Personally for the cost difference, I'd just stick to using the stock plugs unless you're doing mods to your engine and want a different combustion chamber temp, etc. I've never found the claims of "high performance plugs" to be worth it for motorcycles, performance cars, or boats unless you're doing mods. A stock engine will work best with stock plugs...the rest seems to be marketing hype to dupe you into paying more.

 

[Bmeehan19]

I have a set of stock plugs I can gap and install to see if that changes things. I wasn’t sure which plugs to get as there seems to be people for and against each side. Maybe the iridiums are the difference, they are the same heat range etc as the stock plugs, but if memory serves me right I think they are .036 from factory.

The stock NGK plug LFR6A in the 1.8 N/A engines comes factory-gapped at 0.036 yet Yamaha spec calls for 0.031-35 - don't count on a plug being gapped for your needs out of the package. Iridium plugs for my vehicle are pre-gapped but specific to my engine and work properly, but Yamaha doesn't use iridium plugs so it's up to you to choose wisely.

Personally for the cost difference, I'd just stick to using the stock plugs unless you're doing mods to your engine and want a different combustion chamber temp, etc. I've never found the claims of "high performance plugs" to be worth it for motorcycles, performance cars, or boats unless you're doing mods. A stock engine will work best with stock plugs...the rest seems to be marketing hype to dupe you into paying more.

 

[tdonoughue]

A few plug points...
1) the NGK do come pre-gapped. Of course, something might have been bumped in shipping. So it does pay to check but I have never found them out of spec (btw, I don't consider .01 out of spec). But there have been instances where gapping the plugs weakens the electrode and some question whether it is worth touching them at all. I have stopped gapping, do a visual inspection, and have had no issues. (disclaimer: I did have heat soak issues a couple of seasons, and there is a report of someone regapping to the bottom end of the spec with positive results--haven't done that yet, but don't have a big heat soak issue since I run the blower more...)
2) as to the fancy iridium and other plugs--most of these plugs provide you high mileage. If you are smart, you are changing your plugs every 1-2 seasons on your boat--for most people that is less than 200 hours. I would question whether that would even be 10k miles in a car (if you went 70mph the whole time it would be 14k miles). In our application, a long life plug does no good. It will corrode itself into the block and when you go to change it after 5 years you will have a mess. Buy the cheap, normal plugs and change them on schedule.

IMHO, etc.

 

[212s]

In our application, a long life plug does no good. It will corrode itself into the block and when you go to change it after 5 years you will have a mess. Buy the cheap, normal plugs and change them on schedule.

That's a good point actually, especially in saltwater.