Fuel starvation is a real possibility. If your boat is suffering fuel starvation
then it's an unusual form of it due to the length of run time before it starts
becoming noticeable.

Much of the time with fuel starvation it's not described as "boat looses power
after 5 laps" but instead, the description "boat runs great for 1/2 lap (maybe
1-2 laps at the most) and then will only idle - cannot build RPMs" is more
often read.

Routing the fuel line where it once was is worth checking. Also make sure the
tank's atmospheric vent is not blocked or clogged - same for any fuel filter.

I have checked both filter and vent both good, thats what I thought about fuel starvation too

Well I was finally able to get out to our small "play" lake today after I bypassed the water pump and switched to 20:1 fuel. first time out... not enough water was coming through the plumbing so I lowered my pickup. ( I did not take the cooling off my pipe) Top of my cylinder fins are covered in oil/gas so I think my exhaust gasket is leaking or something else. Second run temp is good enough water flowing Third run hatch off good speed until it stalled just coming out of a turn Failsafe I think checked batteries at home and on board cells low. hope to go to the "big lake" tomorrow to do full speed runs for long continuous time.
Gordon

Sunday went out to the "big lake" day was windy, we put buoys out and the race was on haha. My exhaust gasket was leaking a little. as usual the engine lost power after 10 min. brought it in and checked everything exhaust bolts were loose, tightened the bolts and away again. Happened again... loose bolts again...so how do you keep exhaust bolts tight?

Are the engine screws tightened according to the specs on page 12 of the ZEN manual?
Many boaters are relying on the values found on this torque chart.

www.modelgasboats.com/images/s...60_G231_704.pdf

________________________________

Conversion Formula For Nm To Inch LBS.

Nm / 1.3558 X 12 = Inch LBS.
(newton meters divided by 1.3558 times 12 equals inch pounds)
________________________________

EDIT: repaired the link above
EDIT 2: This might work better.

I change from the wet exhaust to a dry exhaust I will torque the screws when I get a torque wrench.

I used a wrench from work...
Went out this afternoon boat ran a constant 27-29 mph. boat use to run mid to high 40's ...mmmm


but the exhaust bolts still loosened

EDIT 1 changed photo
EDIT 2 added text

Today went to the lake, outside air temp 55*, water temp 57* slight breeze. Adjusted tabs down from neutral 1/8", drive up 2* used a 67-105 (3) prop that I used before (last yr) speed full throttle 27-29 mph(gps) My WT-644 carb has had no needle changes, pipe length has not changed from wet (stock) to dry,pipe length is a short 10.5", different header, same tuned pipe (stock WHH wet pipe) now wrapped, stinger id dia is .5", engine temp 178*, gas 20:1, 91 Octane, NKG spark plug looks good, Exhaust bolts loosened last run. no speed change until bolts loosened.(very little flex in pipe ?)

edit video link

I put a sticky note on my PDF manual on page 6 thanks again
Gordon

Gordon
Something still off on that boat - bring it by so I can look at it. I use lockwashers or 'shake' washers - sometimes blue loctite if needed on ours - whats on yours I didn't look when you were over ?? anything?

Maybe on weekend throw one of my engines in or one of the other cylinders I have and well see if it's any better - not sure what exactly is in the WHH engine you have. Or try another carbs I have.

Mike finished his and Elwin is back in action so we'll be out Saturday or Sunday --

RD

sound like a plan I'll text you