BF50A RPM

Author Message   Peter C New member Username: snipergod87 Post Number: 1 Registered: 10-2009 Posted on Saturday, October 03, 2009 - 06:33 pm:    We have a BF50A (50 HP) on out 20 Ft Sweetwater (Pontoon boat). The engine RPM range is 5000-6000 however we never get above 3800-4000 with full throttle. Is this just because of the weight and drag of the boat? Or is it something else? Top speed is 17Mph   mike Advanced Member Username: hondadude Post Number: 166 Registered: 03-2009 Posted on Saturday, October 03, 2009 - 10:52 pm:    What year motor is it? If you do not know...what is the serial number. Is this boat new to you? Has it ever gotten to 5500 -6000? I ask because on 2005 Bf50A's some tachometers did not read correctly without a modification. So...things to check Is the tach set to the correct setting? Different brands have different settings and 2006 and later motors have a different setting than 2005 and prior. Once you are sure everything is correct at the tach... What size prop do you have on the motor? The pitch can make a big difference. Depending on the weight of the boat, the prop should probably be around a 9 or 10 pitch. Any accumulation of algae and buildup on the tubes if significant can slow the boat by a few mph as well as rpm. Weight does make a difference...but with the correct prop, the rpms should get up to where they should be.   Peter New member Username: snipergod87 Post Number: 2 Registered: 10-2009 Posted on Sunday, October 04, 2009 - 12:00 am:    The engine and the boat are new. Just purchased this spring. The prop is routinely cleaned. The boat never exceeded 4000 RPM's ever. How would I test the tachometer? Not sure about the size of the prop and pitch will check tomorrow during daylight.   W D Neal Advanced Member Username: chawk_man Post Number: 240 Registered: 09-2008 Posted on Sunday, October 04, 2009 - 09:10 am:    After the 25 hour break in period, you want to run that engine at WOT (approximately 6000 rpm +/- 300 rpm) as much as possible over the next 100 hours to seat the rings and valves properly. Not getting rings and valves seated properly will lead to long term issues with the motor. Buy or borrow a good automotive tach/dwell meter and check against your instrument reading for the right number of cylinders as Mike suggested. On larger engines mounted on boats with planing hulls, the (rough) rule of thumb is a 1" drop in pitch will get you an increase of 400 to 500 rpm. I would take this problem back to the dealer. I suspect that the prop on that engine was set up for a smaller, lighter boat and the pitch is too high. Get dealer to provide a smaller pitch prop and test the difference.   Peter New member Username: snipergod87 Post Number: 3 Registered: 10-2009 Posted on Sunday, October 04, 2009 - 02:03 pm:    Unfortunately we have just begun winterizing the boat so it is out of the water. I have measurements for the propeller. I do not know how to measure the pitch. Diameter 12" Blades are about 4" in height, 3" in length (like front of the boat to back), Widest part of the propeller is about 5.25" and smallest is 3.5". Is there a part number on the propeller somewhere easily accessible Edit: looking on the outside of the prop is says Honda, and 12.1x9 (Pitch =9?) My Dad estimates the weight of the boat with the engine to be about 2200-2300lbs, but the specs say the engine is about 205Lbs and boat dry weight is 1655 and wet is 2335. So either total weight of about 1900lbs or 2550lbs Boat Model: Tuscany 2086 RE http://www.tuscanyboats.com/swt2086re4.html Engine: http://www.honda-marine.com/modelDetail.aspx?modelGroup=BF50 2.08:1 gearing ratio When idling it is around 900RPM's and the manual says 950 +- 50   mike Advanced Member Username: hondadude Post Number: 168 Registered: 03-2009 Posted on Sunday, October 04, 2009 - 04:48 pm:    I agree with W D...you should take the boat back to the dealer and tell them what is going on. If it is a fuel injected 50, they are able to check the tachometer accuracy with the HDS. They do not even have to run the motor. Just have to turn the key switch on and run the tachometer test. It is part of something that should be done during each motor set up. Many of the boat manufactures just stick the tach in and do not set it for the engine. Maybe they missed it. The prop you have is a 9 pitch and it sounds like it is about right for that boat and motor combination. So, I think your tach is just set incorrectly. If you do not have the time to go back to the dealer or if you are curious...you can check the setting yourself...if you can get to the back of the tachometer. Most likely it is either a Teleflex or Faria Tachometer. If it is a Teleflex you will see a little rotatable switch on the back that has markings like 2P, 3P,4P,5P,6P...make sure the arrow on the switch is pointed to 2P. You may need a small screwdriver to turn it and probably a flashlight to see it. If it is a Faria gauge, the markings on the switch will be 1,2,3,4,5,6...set the switch to 1. You will need a very small screwdriver on this on.   Peter Member Username: snipergod87 Post Number: 4 Registered: 10-2009 Posted on Sunday, October 04, 2009 - 05:48 pm:    Unfortunately none of our vehicles have a trailer hitch to tow the boat except our John Deer Gator (XUV) which is not street legal, and I dont want to have to tow a boat 10 miles with that... I got inside the boat and checked the gauge it is a Faria the setting was set at 2 and I switched it to 1. I will not be able to test the changes until next spring as the boat is on dry land and my Dad does not want to put the boat back into the water just to take it out again. I will notify the dealership and ask them some questions. The thing is this engine came with the boat in a package so I would have assumed they knew what they were doing... Thank you guys for your help when spring comes and the boat is back in the water I will double check to make sure the settings are right. You have been a great help. Edit: The BF-50A is not EFI, has 1 carb per cyl   mike Advanced Member Username: hondadude Post Number: 169 Registered: 03-2009 Posted on Sunday, October 04, 2009 - 06:11 pm:    Glad you found something. The number 1 tach setting is the same as long as the BF50 is 2006 or newer even if it is carburatored. The number 2 setting was for a BF50 made 2005 and before. Don't forget to drain your carburators after your winterization is finished. If you are not sure how, it is detailed in the storage section of your manual.

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