Engine stalls when put in gear

[Rayburn21]

I have a 2008 Yamaha 250 HPDI VMax on my Ranger bass boat. I came down with cancer and the boat set under a carport for two years without being started. It was in Texas and I am in Colorado. We went a brought the boat to Colorado a month ago. the problem I have is the motor will start and idle, some times it you can get the engine to rev up when out of gear, but it stall when put in gear. I took it to a Yamaha dealer to get in fixed, also I had them replace the water pump, service the lower unit, replace plugs and filters. he said he found trash in the air box and that fixed the stalling. it still has the exact problem. the dealer said there was no codes. It was running fine before I came to Colorado for cancer treatment. I'm taking it back to them on Tuesday. Any ideas please.

 

[99yam40]

trash in the air box means mice or something else got in there.
no telling what all they could have done.

make sure the manifold pressure reading at key on is the same as the local weather station report at that time.
change in altitude will affect the fuel to air ratio and power.
will not be able to run the same prop you had in Tx even if the manifold pressure is reading correctly

 

[Rayburn21]

trash in the air box means mice or something else got in there.
no telling what all they could have done.

make sure the manifold pressure reading at key on is the same as the local weather station report at that time.
change in altitude will affect the fuel to air ratio and power.
will not be able to run the same prop you had in Tx even if the manifold pressure is reading correctly

I'm taking the boat back in on Tuesday, I will pass on the information. I understand that the prop will need to be changed at alt, I have lived in Colorado before. right now I can't get it to run above idle, as soon as I give it throttle it dies. Thank you so much for your help.

 

[mike_i]

How's the fuel? Is it two years old? Was it stabilized?