Hi chaps,
This is my first post so I hope it is in the right place. I am relative new to gas boats and have just finished putting together a 43" Aeromarine challenger fitted with a stock 26 cc zenoah engine, stinger and 7016 3 bladed prop. The boat runs fine for approximately 2 to 3 minutes then it seems to bog down, ie slows down with little response from the engine no matter how much you open the throttle. Do you think this could be a carb problem ie high jet to lean or do you think the prop is to large, the stinger is set in the neutral position do you think icreasing the stinger angle may help.Any suggestions would be gratefully appreciated.

Is it running hot after a couple minutes ??...

If u let it sit for a bit does it then run good again??

Is the fuel tank vented??

Just some thoughts .....

It doesnt seem over hot, tank is vented and yes if letit stand and run again it is good again

does it have a fuel filter ... sounds like it's a heat or fuel problem ... I had boat that was good for couple minutes then would get hot and run like cr.p

I used a racing rudder (had water pickup on right side of blade - looking from rear of boat) ... found out later the rudders with pickups on right side pickup water in turns but not on straights .. guess they want engine to heat up on straights

WOuld run for 5 minutes then lose power ... I let it sit would be fine in 10 minutes .... all I did was switch rudders ....runs good now tried carbs, etc first

Send a PM to Scott ... he's the man .... or Daniel at Danielsplace

Did you try the simple things first ... clean carb, new spark plug, new fuel filter

s the boat and engine are new it is probably carb setting. Lean dies rich runs, so open up more. What are your current setting of the carb? Does the boat not come with a instructionsheet of carb settings? If 644 type, H 1,5 and L 1,5 open. Otherwise do a search ion carb settings gigabytes have been written already about it.
When engine dies, can you start it immediately after idt dies or do you have to prime first? If you first have to prime there is probably something wrong in teh tank / hose to carb, or carb malfunctioning. If you do not have to prime first, but pull teh starter about 2 times you are lean.


from Jims Boat DOck

Thanks for the replies
The engine,carb and tank are all brand new, the carb is a 257 and the needles are as factory set,i havent adjusted them. The engine restarted without priming on about the third pull. I am right in thinking the high is 1 5/8 and the low is 1?
A few boating companions keep trying to tell me that the prop is too big and I would be better with a x470 or x460 what do you think?

dave d wrote:That is your problem the carb settings on a 257 are On the low 2.25 and on the high 1 full turn from stop.:dash:

dave d wrote:
Sound VERY much like a vent issue .... Or, an engine running under a enclosed deck with too much exhaust system heat and a lack of effective fresh air intake ?

SOunds like carb settings or too much heat - Like Scott / Marc / Randy said

check carb and tank vent

Yep I would set the 257 to 2-1/8 on Low and 1 1/8 on High. That's a bit on the rich side but it will run...tweak it from that point on. If that doesn't work, definitely look at the tank venting system. Sure does sound like a vent issue, but since your carb settings are so far off, it's more than likely running lean and overheating...thus the sluggish behavior after a few minutes. Set the carb before you end up doing permanent damage to the engine. Also, if you're not already aware of this, run a good quality oil at about 8oz per US Gallon. (about 16:1 ratio). Makes good power and will save your engine in situations like this one, with carb set too lean.