Where do I start? Boat motor RPM

I recently purchased a 1995 stratos 278dc with a 1999 Evinrude Fitch 150hp motor. I run at 4700-4800 rpm at a top speed of 47-50mph. The boat came equiped with a hot foot and a 4 blade renegade SS prop. The last trip out there was only two of us and minimal gear with both livewells empty. After talking to a gentleman today that works at cabela’s, he informed me I should be running 5200-5600 rpm at top speed with this engine. At 4700rpms he said the engine is lugging too hard and it will be bad for the engine. Could it be the hotfoot isn’t adjusted properly? Maybe the tach’s not properly working?(sems to work right at idle-1000rpm’s) Not the right prop? One thing I must add is the engine had over $3200 worth of top end work done last july and has less then 15 hrs break in (previous owner told me). Where do i start looking for the problem with the low rpm? The mechanic that did the work is one of the best in the area, but he is 75 miles from me so i didn’t want to drive it all the way there to have him take a look at it. Any advice is greatly appreciated. Thanks

SOUNDS TO ME THAT YOUR NOT PROPED RIGHT. WHAT SIZE PROP YOU RUNNING? ARE YOU ALL TRIMMED UP AT THAT LOW RPM?

I’m running a newer ficht 150 and my books says at wot rpms should be 5200.

I’ll dbl check on my prop size, but i’m pretty sure its a 3 blade raker 21″.

I know when I was testing props, the 4 blade would pop me out of the hole like crazy, but I lost a lot of top end and my revs weren’t high enough.

I’ll dbl check tonight and respond again.

The testing was done on an 18′ Lund pro v.

Jami

I believe the RPM range is stamped on the Motor Spec plate on the transom mount.

Both the RPM and top speed sound way to low to me. I had a stratos 273 with a 150 that ran in the low to mid 60’s. I believe that the RPM on mine was pushing near 5400 at top speed. My guess would be wrong prop size or pitch. Or you are not fully fully trimming it up. Those #’s sound more like the the un-trimmed #’s

The prop is a renegade 13 1/2 x 23 four blade ss prop. I am new to a boat this large so I adjusted my trimming by keeping the trim guage needle level with the boat in the dial indicator when on plane. Should I be trimming it so the needle points above or below the boat and watch the rpms? If so , does this mean the trim guage is off? Maybe the hot foot needs to be adjusted to open the throttle more? Thanks for the help.

PUT TAPE OVER THE TRIM GAUGE. FORGET IT! GO BY FEEL. TRY RUNNING IT AND SEE IF WHEN YA TRIM UP YOU CAN GET YOUR RPMS UP TO 5200-5500 RPM. THE ONLY TIME I LOOK AT MY TRIM GAUGE IS WHEN I START OFF. JUST TO SEE THAT I’M TRIMMED ALL THE WAY DOWN. YOU’LL FEEL WHERE TO SWEET SPOT IS. THEN CHECK YOUR RPM.YOUR RPMS AND SPEED SHOULD PEAK AT THE SAME TIME,

I will try that next time and see what i get for rpm and speed. When you say you are trimmed all the way down on take off does that mean the guage reads below the boat? I might be taking off wrong. I always trim the boat level then trim down as I take off. Is this right or should I trim all the way down then trim up as I start planeing out? Thanks

YA I THINK YOUR DOING IT BACK WARDS. NEXT TIME FORGET THE GAUGE!!!!! ACTUALLY LOOK BABCK AT THE MOTOR AND TRIM ALL THE WAY DOWN.(SO THE PROP END IS TUCKED UNDER) HIT THE THROTTLE WHEN YA GET UP ON PLANE START TAPPING THE TRIM BUTTON UP (STILL NOT LOOKIN G AT THE GAUGE) KEEP TAPPING THE TRIM UP UNTIL YOU DON’T SEEM TO BE GAINING ANYMORE SPEED. NOW LOOK AT THE TACH AND SPEEDOMETER. NOW RECORD THE RPM AND SPEED IN YOUR MEMORY. (NOW YA CAN LOOK AT THE TRIM GAUGE.)THIS WILL BE THE SWEET SPOT WHERE YOU WILL GET THE BEST MPH- AND MPG. CAUTION DON’T TURN SHARPLEY TRIMMED UP THIS HIGH. WHEN YOU ANTICIPATE TURNING TRIMM DOWN SLIGHTLY. PRACTICE THESE SEQUECES UNTIL YOU FEEL COMFORTABLE. PRETTY SOON USING TRIM WILL BE NATURAL TO YA. I ALLWAYS HAVE CONTACT WITH MY TRIM SWITCH. WITH AN EYE ON MY LOCATOR I NATURALLY TRIM UP IN SHALLOW WATER. LEARNING TO TRIM WILL SAVE YA ALOT OF DAMAGE ON YOUR PROP-LOWER UNIT TOO! AND GET THE MOST PERFORMANCE OUT OF YOU OUTBOARD. I HAVE A BLINKER STYLE TRIM SWITCH ON MY RANGER SO I DON’T EVEN HAVE TO TAKE EITHER HAND OFF THE STEERING WHEEL. THIS STYLE OF TRIM SWITCH IS REALLY NICE. ESPECIALLY SINCE YOU HAVE HOTFOOT. LET ME KNOW HOW YA COME OUT OR NEED HELP.