Low rpm

[Beamer50]

I have a tracker v14 with cockpit. Just took off 25 hp mercury 2 stroke and hung a 40 hp mercury 2 stroke, only about 5 mph speed increase and 3900 rpms with 17 pitch prop. I just raised the motor 2 inches. Will that help with rpms and speed? I was hoping for 5000 rpms and 35 mph at wot with 17 pitch? Want to run half throttle, saving gas and 25 mph . Have not had boat out since raising 2 inches
Barry

 

[racerone]

First need to establish the condition of the 40 HP motor.-----To raise RPM you reduce pitch of the prop.----Try a 13" pitch.

 

[Beamer50]

Had a 13 , came off a pontoon barge . Lucky to get 19 mph with 13

 

[racerone]

Do some inspection / trouble shooting on the 40 HP.

 

[Scott Danforth]

is your new to you 40hp the same leg length as your old motor?

 

[briangcc]

Not sure why you're hung up on using the 17" prop. If its truly running 3900 you're lugging the motor...big time.

For giggles, I ran your combo through Merc's prop selector and took an educated guess on a couple of items. Everything is coming back at starting at a 13" prop.

From what I'm finding on the Tracker V14, 20-25HP is max for that boat. Did you check your capacity tag?

 

[Beamer50]

What i meant was this 40 hp came off a pontoon with a 13 pitch prop. I put a new 17 pitch and it should do better than what its doing. No Cavitation. No slipping ???
Barry

 

[Beamer50]

Yes , both long shaft measuring the same

 

[racerone]

Find out what is wrong with the 40.----Post the compression numbers and check for spark.

 

[jimmbo]

5mph increase with 15hp increase is actually very good. I suspect you have way too much pitch, which is holding the rpms down

What yr is the 40hp? 2 cylinder?

 

[Scott Danforth]

And everyone is ignoring the pink elephant in the room....

From what I'm finding on the Tracker V14, 20-25HP is max for that boat. Did you check your capacity tag?

What i meant was this 40 hp came off a pontoon with a 13 pitch prop. I put a new 17 pitch and it should do better than what its doing. No Cavitation. No slipping ???
Barry

going up in pitch adds loading

 

[Scott06]

What i meant was this 40 hp came off a pontoon with a 13 pitch prop. I put a new 17 pitch and it should do better than what its doing. No Cavitation. No slipping ???
Barry

verify the 3900 rpms is correct if so you need to go down in pitch to get rpms up to hit correct WOT rpm range. If you still have the 13" I would try it to see how it reacts.

As far as motor height do you have the cav plate even with bottom of boat? I could see it slowing top speed if it is too deep but I don't think it would affect rpm so much

 

[Scott Danforth]

Yes , both long shaft measuring the same

Your boat is listed with a 16" transom height. So the motor should be a short shaft

 

[Beamer50]

Sorry, my mother is a short shaft and rated max 40 hp . Just tuned and timed it . Runs great, no cavitation from wot take off ? I've had boats where I use my 19 for pulling skies and my 21 pitch for speed / less gas consumption, Baya spelt wrong, 19 ft.
I've always had 2 props

 

[Beamer50]

5mph increase with 15hp increase is actually very good. I suspect you have way too much pitch, which is holding the rpms down

What yr is the 40hp? 2 cylinder?

2002 _ 2 stroke

 

[Beamer50]

Do some inspection / trouble shooting on the 40 HP.

What do you suggest ? 135 compression on both cylinders ? Timing is supposed to be correct set by shop mechanic ?

 

[Beamer50]

Also , I would think I'd get cavitation on wot take off like I have before on other boats if to much pitch ? Wouldn't you?

 

[Scott06]

Also , I would think I'd get cavitation on wot take off like I have before on other boats if to much pitch ? Wouldn't you?

Too much pitch doesn’t cause cavitation on holeshot, just causes slow acceleration.

 

[Scott06]

Sorry, my mother is a short shaft and rated max 40 hp . Just tuned and timed it . Runs great, no cavitation from wot take off ? I've had boats where I use my 19 for pulling skies and my 21 pitch for speed / less gas consumption, Baya spelt wrong, 19 ft.

Your mother is a short shaft? Not sure what you meant

different boats different pitch is required. Do you know if the gear case ratio is the same between engines?
again is cavitation plate even with bottom of boat ? Then motor is set ok , (maybe not optimized). If you only get 3900 rpm u need to go down in pitch

 

[Beamer50]

Motor is short shaft not mother, yes cavitation plate is bottom and center
How can I find out the gear configuration? Model # 0T518996 for the 40 hp mercury max rpm 5500 and 0t935153, 25 hp 6000 max rpm