help with my engine

[Dave Gilles]

so pretty new to gas boats. I have a 26cc that wont run when hot. if you can get it to fire off it dies immediately. even then has to be choked a ton. once cooled back down fires right up and runs through a whole 500ml bag. some back story its a used engine I blew it up a month ago running it onto the shore when the radio box switch glitched. New top end installed, fresh carb, fresh diaphragm, no leaks in the bottom end and cases torqued. tried a 2nd carb, same issue. carb isolator not blocked or upside down gaskets used and could be replaced but seem adequate. all fresh seals on the exhaust. fresh gas, I put the last batch on the shelf and got brand new gas to start over with. fresh plug NGK CR7H. tried 2 different pickups.

coil? it also kind hunts at idle revving high for a bit then low again. worse when hot. needle settings Ive tried are L- 1.5 out to 2.5 out, generally 2-1/8 out. H needle 1-1/8 to 1-1/4 out. WT257 carb....again new diaphragms and cleaned out screen, rebuild kit. runs fine on the water, just wont start after a run. has to cool all the way down.

 

[John Beardslee]

Sounds like a bad coil to me.

 

[Howard Larson]

Check for air leaks! Carb spray or similar at all sealing points.

 

[Kevin Sheren]

You may have a crack or warped isolator block. start your engine spray brake cleaner on the isolator block. If it is bad you will hear it. you might want to spray the crankcase seals with it running as well.

Kevin

 

[Danny King]

It sounds like an air leak.

 

[DON MAHER]

Definitely an air leak from your description, more than likely the isolator block is warped.
Try block sanding and new gaskets.

 

[Dave Gilles]

So we tried a borrowed coil today and not only did it fix it, the boat picked up significant speed.

 

[Kevin Sheren]

Dave try what I said in my earlier post. You will find the air leak. It will save you from chasing your tail.

Kevin

 

[Drew St. Amant]

I had similar symptoms then this happened

 

[john v]

Been there, done that

 

[LeeWininger]

These motors can be a bear to refire hot or flooded..... that being said a 257 generally likes 2 L 1 H on carb settings

 

[David Ashcroft]

I had similar symptoms then this happened View attachment 321185

Happen to my 30.5 Zen ,,,the whole cooling jacket was hanging by a thread.
Was too thin.after mod.