Late 80s Black Max

[mulliganmagic]

I've been told that our motor is several different years in the late 1980s and possibly early 90s. It is a 150 hp XR2 Mercury Black Max. I'm not completly sure but I do have the s/n. If anyone could help me determine the year by the number I would be very greatful.<br /><br />Serial Number: A905844

 

[rickdb1boat]

Re: Late 80s Black Max

150 XR2 A905191 - A969903 1986 V6

 

[mulliganmagic]

Re: Late 80s Black Max

Thanks RB. Thanks for looking up the s/n for me. I have another question though: What is the best size prop for this engine right now it has a 23p stainless steel on it right now. Thanks again.

 

[AndrewB]

Re: Late 80s Black Max

Prop size isnt a simply answered question. We'd need some info first like what you mainly use the boat for - fishing or skiing but more importantly what are you engine revs at WOT (wide open throttle) if you have a tacho connected. Ideally at WOT your engine should be within the WOT rev range for that motor - Id assume round 5800-6000 on your motor but someone should be able to clarify that for you.If your not reaching this, youd need to prop down, if your over - prop up. Some people use lower pitched props if they mainly ski for better hole shot speed but the WOT revs must be kept an eye so you dont damage your motor - hope this helps

 

[mulliganmagic]

Re: Late 80s Black Max

Andrew, thanks for your reply. We've only had the boat out once since we bought it and we proabably need to try this prop once more before trying another prop. However, on our test run the water was very choppy and we had to trim the engine all the way down to pervent porposing. The manual states that max rpms should be between 5000-5500. On our test run we fell just short of 5000 rpm with the engine trimmed all the way in. Also, it is a fish and ski boat so we are going to use it for fishing until the water warms up enough to ski and then we will most likely be using it for both once sking season starts. We proabably will not troll with it though due to the fact that the boat has a very nice electric trolling motor. Thanks for your help.

 

[BF]

Re: Late 80s Black Max

It sounds too me like you could use less pitch. Not getting to 5K rpm with sounds too low. I have a 17' ski boat with '82 150 hp V6. We run a 19 pitch aluminum (standard 3 blade prop). It revs out to about 5800. It will do ~50 mph without trimming up, and a few more mph by trimming. The boat just jumps on plane (it's quick out of the hole and builds rev's quickly). Maybe we'd gain a few mph by going up in pitch, but I care less about top speed than having a responsive boat that pulls well.<br /><br />Hope that helps.<br /><br />Brent

 

[AndrewB]

Re: Late 80s Black Max

Brents pretty much hit the nail on the head. The only further advice I would give is to thoroughly test the boat in all conditions first, including pulling a ski or two.You mite want a lower pitch depending on your hull as not all hulls are the same. Also speaking of hulls, you may be suprised how much trimming out will effect your revs. Ive got a deepish hull 17' ski boat -trimmed all the way in barely gets over 4 grand - trimmed out over revs to 6. So just play around a bit first. Good luck

 

[rickdb1boat]

Re: Late 80s Black Max

It's always a very good practice to carry a spare prop anyway. So why not get yourself an aluminum 19" prop(Cheaper than stainless) as a back-up and then you can change over to this one before you plan on a day of skiing. This will give you more holeshot and I you will not have a problem over-reving the motor with that pitch, especially with a few people on board. It would affect your top end revs by about 400 RPM's. That would still keep you in the ballpark of you Max. rev range. Besides, nothing says you HAVE to run it at full throttle anyway at top end. Just watch the revs...