99 degrees, 108 heat index, 58% humidity, and about 85 degree water temperature. Does this have that much of an effect on RPM's?

I only see 7230 r's with a D-plate and a 13/19 and 6970 or so with the 14/20. I don't like running that low.

Will

whats your elevation?

I had the same thing this weekend. It was 96 degrees, 98% humidity, dew point was 76 degrees. I lost at least 150 rpm! I assume this is normal?

Yup that is about spot on to what I have been getting..

Yep sounds normal to me, I dont know exact numbers but the heat + the humidity especially really really kills the engine. The better it can breath the better it runs and better numbers it puts out. They really like those low temps and low humidity. Water temp can affect you as well.

I hope thats the case. I've ridden my ski twice since it's been modded...first time was up in LI and it was like 98% humidity, the other time was Saturday during this friggin heat wave...both times I've hit 7200rpm----I'd do a back flip if I hit over 7300rpm when this cool weather comes in.

from my experience you'll have to lean out the highs when its warm and humid to get any reasonable rpms and then when the air gets "good" you score a few pistons unless you richen up hte highs.

Thats why the factory settings are so rich this time of the year. However those same settings will accomodate 50 degree weather without seizing..

FYI Air temp does affect HP some but the real killer of HP is the high humidity/ air density (The amount of water in the air) You are having to burn all that water/mosture in your motor and the combustion of the fuel/ air not as efficent as a nice day with low humidity/ air density So those nice dry fall days will give you those big numbers you lost in the hot humid days Tip when the weather changes to drier air richen that ski a little so you won,t be too lean. an 90 degree day with 30-40% humidity will give you more Hp/rpms than an 80 degree day with a 80-90% humidity!

Thanks all. I figured as much. I was seeing 7390 with this set-up and a 13/19 last fall. I was just a little worried. As for elevation, I am at 445' above sea level. Highs are at 1 turn. I will deffinitly richen them back up when the weather changes. I am running the 14/20 right now at 6950-7000 r's. I think I will switch back to the 13/19 till the weather gets a little better. I don't like seeing the 6900's. Once again thanks all. You to Tommy!

Will

2fast4you wrote: a 90 degree day with 30-40% humidity will give you some more hp/rpms than a 80 degree day with a 80-90%humidity Will, these are the same "perfect" weather conditions that i have to face day by day here in my country so after reading this I think that the 70 mph figure that i achieve with my single pipe boat in the past was not so bad after all....

70 mph right now would be amazing! I hit a best of 74.1 mph with the D-plate last year running a 14/20. I will have that back as soon as the weather breaks. I do recall though that it was like 65 degrees and no humidity. I was turning like 7160-80 r's or so with the 14/20.

Will

I'm down 100 to 150 rpm from cool spring weather with minimal humidity. Stock engine running at stock carb settings.. Essentially running rich right now..

LM
I tried taking a compression test on my boat the other day during a rare Canadian heat wave (100F). My Mac guage showed 128-130lbs WTF. I checked again a week later in 72F weather and got 140. BTW I also lost 100 rpms during the hot weather.

Terry