House Speaker Thomas P. (Tip) O'Neill (D-Mass.) toured the Chesapeake Bay by boat for more than two hours today and declared afterward that federal funding is essential for cleaning up the Chesapeake's polluted waters.

O'Neill said Congress needs to make "a long-term commitment" to projects such as the bay clean-up. "This is something Americans should have been doing 25 or 30 years ago," O'Neill said.

Legislation that would provide $52 million for the bay has passed the House and awaits Senate approval, which is expected before Congress adjourns in early October.

The visit here by Congress' highest ranking Democrat, who was escorted by Democratic Rep. Roy P. Dyson of Maryland's Eastern Shore, reflects an increasing political sensitivity to environmental issues in this election year.

President Reagan has been dogged by criticisms that his administration lacks concern for protecting the environment. In his State of the Union address, Reagan announced that he would ask for bay-cleanup funds.

O'Neill, who insisted that he was "not out here to talk politics," said he was unaware that Reagan had made a similar visit this summer. Dressed in a red sport jacket and smoking a large cigar, O'Neill cruised the bay aboard the Stanley Norman, an 82-year-old skipjack used for dredging oysters during the commercial fishing season.

"I am amazed at the amount of the economy that comes out of the bay," O'Neill said, citing watermen, restaurants, waterfront property owners and recreational boaters as some of those who make the bay a $750 million natural resource.

Dyson said the cleanup project had gained momentum this year because of cooperation between officials from Pennsylvania, Maryland and Virginia and the federal government.