prop change in high altitude

[DAG]

I have a Chaparral 183 with a Merc 4.3, 14.25 inch prop with 21 pitch.<br />I live near Sacramento and do most of my boating here at about 400 feet of altitude. <br />We are going to Tahoe next month and I plan to bring the boat. The altitude is about 5000 feet. <br />Do I need to get a different prop?<br />Thanks,<br />Doug

 

[Realgun]

Re: prop change in high altitude

Most of the time you will need to drop to a 19 to get some of the power you lose getting higher up. Top speed will not be the same as at sea level for sure. Also is that an EFI engine? If it is no worried if it is not then your going to run rich and burn more fuel. If you have a carb you may want to change the jets.

 

[QC]

Re: prop change in high altitude

I normally boat at around 500 ft. and ran a carbed 140 OMC at 6800 feet and got away with the exsitng prop and without rejetting, but she really struggled. I had an EFI 5.7 Merc that ran great and 2 inches less of pitch was just perfect.

 

[RichP1269]

Re: prop change in high altitude

When we take my father in laws Marlin Chinook to Lake Tahoe, we drop to a 19 pitch prop and change out for hotter plugs. No problems so far. Motor is a 260 HP Merc I/O with a Alpha outdrive.

 

[DAG]

Re: prop change in high altitude

Thanks for the help.<br />-Doug