Hello Mark,
No; the fact that your work experience does not match the degree that you hold, will NOT have a negative effect on your qualification assessment.
The fact that you completed four years of post-secondary education is primary and a criterion all by itself to give you more points. The field of study is not primary.
And, the good news for you is that you have 8.5 years of work experience, which by itself, is also a separate criterion for more points. As long as you have proof of your work experience, which usually is backed by certified/notarized reference letters from your employer or immediate supervisor stating your job title(s) and responsibilities, you should be fine. Also, make sure you have your salary pay-stubs, or some other kind of ADDITIONAL proof for your job(s). Job Acceptance letter(s) that you received is also proof.
Mark, if you have not already done so, please follow any of the web links below to take the FREE self-assessment test, or if you prefer and you have the time, you can do both. The links are from different entities.
This first link from the Government of Canada website will let you do a self-assessment on whether you qualify for the Skilled Worker Simplified Application Process - Click on "Take the Test" at the bottom of the page:
http://cic.gc.ca/english/immigrate/skilled/assess/index.asp
This second link from Canadavisa.com website will also let you do a self-assessment for the Skilled Worker Simplified Application Process. Use this second link if you would like to have a personal feedback sent to your email from the law firm that operates Canadavisa.com:
https://www.canadavisa.com/assess/canada-immigration-assessment-form.htm
When you have the time also, please browse and familiarized yourself with the following websites:
http://cic.gc.ca/english/index.asp
http://www.canadavisa.com/
Also, feel free to browse the topics in this forum, and ask questions so that the pros here can help you. I will suggest that when you have the time, please read the following posts under the stated subjects for the related Immigration threads as follows:
General - All Canadian Immigration; Subject: Immigration Acronyms
General - All Canadian Immigration; Subject: CAIPS Codes
Skilled Worker / Professional Immigration; Subject: Prepare an Interview
Good Luck in all of your endeavors.
Warm Regards,
Libra.