DVS7OY Posted October 11, 2012 Share Posted October 11, 2012 Hi Guys, I'm just after some advice regarding prop selection, i have a brooker 435 with 40hp 2004 Mariner. I've had a look at what prop i currently have and it reads - 816702A40P12 mercury, making the assumption that it is a 12 pitch prop. It currently rev's out at 3000 at top speed. The boat doesn't have any trouble getting out of the water. Been searching online shop but not sure if i need a 13 spline etc. Any advise would be appreciated. Link to comment Share on other sites More sharing options...
chrisg Posted October 11, 2012 Share Posted October 11, 2012 You need to pause a moment before you go on. That's a 12 pitch prop but you need to check if you tacho is reading properly as that motor should be reving to at least 4500rpm if not 5000rpm Either there's a tacho issue or a motor issue - either way get it checked before investing in props. C. Link to comment Share on other sites More sharing options...
dunc333 Posted October 11, 2012 Share Posted October 11, 2012 yeah revs sound a bit low there,also check that the motor is at correct height on transom before prop selection.you should be able to see cav plate up on top of the water when the boat is on the plane,or when boat is on trailer the cav plate should be no lower than bottom of hull. cheers dunc333 Link to comment Share on other sites More sharing options...
a boat Posted October 11, 2012 Share Posted October 11, 2012 Hi, if th boat can get on the plane and cruise fine you will be seeing more than 3K RPM so most likely your Tacho is faulty or on the wrong setting. At 3000RPM you would not even being planing with such an engine on such a boat and a 12 inch prop would turn more RPM than that if running right. Also there are three 40HPs your engine could be so without knowing if it is the 2 cylinder, the 3 Cylinder US engine (which is the best of the three beign the de-tuned 60HP) or the TMC 3 Cylinder it is hard to say if that is the right size, but it would be close. You want to see about 5500RPM at WOT. Cheers, Huey. Link to comment Share on other sites More sharing options...
oz_brett Posted October 11, 2012 Share Posted October 11, 2012 (edited) Huey can also type faster then I do, while I typed the message saying talk to Huey he had already replied! Edited October 11, 2012 by oz_brett Link to comment Share on other sites More sharing options...
DVS7OY Posted October 12, 2012 Author Share Posted October 12, 2012 Hi Guys, Thanks for all your replies, is there a quick test that i can preform to see if the tacho is faulty? May have a look tonight at the back of the tacho and post a pic from memory only setting was 2 or 3 cyl. Link to comment Share on other sites More sharing options...
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