am i really underpowered

[bout time83]

hi all, my question is i have a suzuki df25 vtwin pushing a 16ft alumaweld all welded hull bass boat style. the problem im having is its sits very low in the back just sitting there even worse on plain. the transom height is 21in the motor is a long shaft. my cavitation plate is about 1in under the bottom of the boat. at wot the the plate above the cav plate is about 1in under the water dragging big time. prop is 10.25x10 and im pretty sure the alarm is over rev warning (no tach). how can i get the back of the boat up? ive already gutted everything but the front deck to try and lighten weight. she gets to 21mph max after playing the tilt adjustments with me 185lbs my buddy 165lbs 6gallons of gas in middle and battery up front. the boat is rated for a 60hp but i dont nothing like that i fish shallows. smart tabs,flotation pods, dol-fin?? or can i lift the motor on the transom say 2.5in?

 

[AGENT 37]

Re: am i really underpowered

Start with raising the outboard. The anti-ventilation plate should be level with the keel of the boat, not below it. My best results seem to have been mounting the engine with the anti-ventilation plate 1/2" -1" above the keel of the boat. The rule of thumb is that for every 12" the prop sits back from the transom you can lift it 1" and still get good bite with the prop...... to a certain point.

If you are over-revving the outboard it is only going to get worse by mounting the engine higher. You need a steeper pitched prop if you are turning too many RPMs....... either that or you will need to back off the throttle. I can't tell you anything about the alarm......

Is your boat an actual Alumaweld boat, or is it simply a welded aluminum boat? Just wondering for weight estimation purposes.

 

[99yam40]

Re: am i really underpowered

Running less than 1/2 of the rated HP is under powered

 

[JB]

Re: am i really underpowered

Running less than 1/2 of the rated HP is under powered

Agree. You need ay least 70% of rated power for satifactory performance. I wouldn't use anything less than 40HP on that boat.

 

[1979checkmate]

Re: am i really underpowered

get a tach as well.

 

[bout time83]

Re: am i really underpowered

Thanks for the replys, yes it is a alumaweld boat they say 545 is the dry hull weight I've gutted it all excecpt the front deck so I had to have taken at least 100lbs out. We put my buddys 25 short shaft on it and it hit 27mph no prob with 13 pitch prop. So I was thinking of doing a 13 pitch and so does suzuki dealer and lifting the motor about 2in. The reviews I read so my same motor on a 20in transom but they had to use a mini jack set at 3.5 in high. So would smart tabs help pick up the rear of the boat? The old 50hp was 188lbs and now the 25hp is 168 and half the hp but she jumps out of the hole fast but I need at least 20in of water or I'm dragging.

 

[RRitt]

Re: am i really underpowered

i think its the suzi. isn't the suzi 25 an extremely heavy engine? the engine is probably too heavy for the boat. you could put a bunch of weight up front so that it doesn't plow as bad and that might help. But .... it's never going to be as fast as your buddy's lightweight 2stroke. Now is a really bad time to be buying new enignes in the 25-40HP range. EPA regulations have them weighing too much. Better off to buy a used 30HP 2 stroke and wait for the next generation of four strokes.

 

[JB]

Re: am i really underpowered

i think its the suzi. isn't the suzi 25 an extremely heavy engine? the engine is probably too heavy for the boat. you could put a bunch of weight up front so that it doesn't plow as bad and that might help. But .... it's never going to be as fast as your buddy's lightweight 2stroke. Now is a really bad time to be buying new enignes in the 25-40HP range. EPA regulations have them weighing too much. Better off to buy a used 30HP 2 stroke and wait for the next generation of four strokes.

The boat is rated for 60HP, RRitt. They weigh up to 350#. I see no way that any 25 on the planet is too heavy, but I do see a 25 unable to get it fully on plane and an overlength leg causing too much drag, leaving the stern wallowing.

The boat needs to be correctly rigged with a suitable outboard, be it 2 or 4 stroke.

 

[RRitt]

Re: am i really underpowered

The boat is rated for 60HP, RRitt. They weigh up to 350#. I see no way that any 25 on the planet is too heavy, but I do see a 25 unable to get it fully on plane and an overlength leg causing too much drag, leaving the stern wallowing.

The boat needs to be correctly rigged with a suitable outboard, be it 2 or 4 stroke.

25hp is plenty to push around 850Lbs on a 60" beam. The fact that his buddies engine goes 27mph is a clear indication that his problem is something other than raw horsepower.

A 450lb hull with a 180lbs tiller engine with a 185Lb driver is going to be nose up and plowing. My little flats skiff is rated 90Hp but the reality is that if I hang anything over 110 lbs then i have to start counterbalancing the hull.

 

[pootnic]

Re: am i really underpowered

Just happened to be on youtube and a 25hp pushed a 16.9',5'10 beam,960lbs semi V ,28.1 mph.(boattest dot com)
Happened to be an etec,maybe the Vtwin isn't setup quite right yet?
Is your boat 60hp rated for a console and is the Vtwin a console...the 25hp test was a tiller.
Prop change,motor height,shifting weight might be the ticket but a tach is your best friend here.
Good luck,maybe try the Suzuki forum see what people think there.

 

[bout time83]

Re: am i really underpowered

Sorry i forgot to update this.. A year ago... Thanks for the help and tips. Heres what i did, new prop 13 pitch (fixed the alarm she was over revving), lifted the engine on the transom about 2in. The boat was a console but now its a tiller. With those fixes.... WOW! Night and day difference! 28mph with 2 people and gear! The 2strokes get the jump on me for about 3seconds then the 164lb 4stroke blows by and i get to fishing first. The bigger pitch also fixed the rear sagging when on plane, it does still plow a little at slow speed with just me but i can live with that and to think this motor is lighter then almost all the other 25hp 4strokes.

 

[MattFL]

Re: am i really underpowered

Thanks for the follow up. Move some weight to the front. Put your gas tank and battery up front if you can. Or toss a 5 gal bucket of water up there. A slightly heavier boat that sits flat will perform much better than a slightly lighter boat that squats. With small boats it takes a little effort to keep the weight balanced when you switch between a full load of people and just yourself.