Again Im unsure of the 25cc poulan. Is the engine based on the homelite 25cc? Alot of these engines are in many models of trimmers because one company owns several brands. I'll let you in on a secret, If you havent bought any motor yet, buy the homelite 30cc. They arent made anymore but you can get them for cheap on ebay. Look for homelite pressure washers, they are all 30cc and they stink as pressure washers but the motor is almost the same in weight as the 25cc but can make almost 1000rpm more with the same prop over the 25cc. I bought one new and one used but slightly both for $26 each. The 30cc were in some of the trimmers also but there model numbers arent always clear but any washer has the 30cc. I've got all I want so I dont mind letting it out on how to get them. If they were in the r/c boat section of ebay they go for upwards of $100 in any running shape. If you get any engine you know you have to free up the exaust and get a larger carb, Pete at www.wackerengines.com can set you up on the cheap with carb, mount ,muffler and prop hub for most any engine. Give him a call, his number is on his site and he likes to talk on the phone rather than play email tag anyway. Piper

OH! On the ryobi 31cc. There great motors for the right install. Im using one on my 1/4 scale Cub because they lug a huge prop and everything is in cowl, but for brute thrust I think the homelite is a tad bit better.