3l merc WOT 3500 no plane

[Julto]

Hi ervyone, my boat is a Baja islander 180 3.0l mercruiser,prop 14inch x19pitch 3blade

At wot my engine rev at 2000 and the boat wont plane. Passenger have to be seat at the front of the boat to get on plane ,then it rev at 3500 rpm max at 35mph Is that normal? Plug are good ,distributpr is good,timing is good. I cant find my problem. Should i try to lower prop pitch to get the boat to plane faster? Or my problem is somthing else?

 

[Pete104]

Serial number & pics will help. But you are so far off recommended WOT something isn't quite right.

 

[Julto]

Engine sn 0f063067. Drive sn 0d797041

 

[Pete104]

Engine compartment pics! How long have you owned this boat? I can't do anything with the numbers right now.

 

[Julto]

First season with that boat









Best i can do

 

[Pete104]

Things look normal in there. Only thing I see the drive doesn't match the bell housing. Should be able to find a gear ration on one of the "mercruiser" stickers. You are looking for something close to 2:1.

 

[Julto]

There is no ratio number on those stickers. All i can find is an sn 0f086117

 

[Pete104]

Do you have the key for the drive lock? Just asking.

 

[Julto]

Actualy no, i will try to contact the last owner.

 

[Pete104]

At this point you need to figure out what gear ratio the drive is. With decals replaced, gonna have to do a tooth count.

Drive straight down. Shifter in forward gear & spark plugs out of motor. Remove top cover. Those bolts aren't all that tight but may have corrosion on them so if they fight you don't force them. Either suck enough oil out or drain it completely. Your looking to count the teeth on the horizontal shaft. Your going to have to give it atleast 1 full revolution. Mark a tooth and count each tooth as your turning the prop CCW .

 

[thumpar]

The serial number comes back as a 1.98:1 ratio. That doesn't mean it didn't get changed but that is what it comes back as.

 

[Alumarine]

I don't think you can be going 35mph at 3500 rpm with that boat/motor no matter what gear ratio you have.

Are you using a GPS to measure your speed?
Can you hook up a different tachometer to verify yours?
Is your motor trimmed all the way in when you're trying to get up on plane?

 

[thumpar]

I didn't catch the speed part. There is no way you could be at 35mph and not on plane.

 

[stonyloam]

OK at 3500 rpm, 19" prop 1.98 gear ratio, 12% slip will give you 28 mph. Either tach or speed is not correct. To actually be doing 35 mph you would need about 4,400 RPM. Do you trim down to get on plane?

 

[Julto]

I did som test yesterday ,wot around 3400rpm 30mph with 2 people in the boat. The problem is that the boat will rev to 2700 with trim down and wont plane and take speed unless somone seat in the front to add som weight.

I think i should try a 17pitch prop. I will be able to rev more and have more power to plane,what do you think?

Im trying my best to write and speak in english ,thx again.

 

[fishrdan]

That looks like a SS prop to me, and if so, it's going to load the engine like a 21P aluminum prop. I wouldn't jump down to a 17P prop as that may be too aggressive, though it's better than lugging your engine like the current prop is most likely doing.

Are you boating at altitude, if so what if the elevation? Also, you may want to run the boat/trailer down to the scales and have it weighed and see if it's close to manufacturer specs. (A water logged boat can have bad performance.)

WOT of that engine is most likely 4400-4800RPM, it's about 1400RPM shy of where it needs to be, so you may have multiple problems. IE: wrong prop & bad tach.

I'm running a 18P 4-blade Alpha 4 prop on my 140HP Mercruiser (basically same engine as yours) on a 18'er that's most likely heavier than your boat, and it works great. Not saying that it's going to be the cure-all or a good match for your hull, but it's a good stern lifting prop that gets the boat up on plane quick. I also have a 16P 4 blade Michigan Wheel for when I have a heavy load and water skiing, or going to high elevation. The 2 props respond very different, the Alpha 4 is very well mannered and planes the boat relatively level, while the Michigan 4-blade points the bow into the sky while planing...

 

[thumpar]

At 30 MPH you should be on plane. Do as fishrdan suggested and get it weighed.

 

[Heavy<313>]

I think we are having a bit of a language barrier according to the OP: "When I holeshot my RPM's won't go above 2000RPM and the boat won't plane, once I have someone move to the front of the boat the boat will plane and accelerate to 3500 RPM"

 

[Rick Stephens]

Julto,


Your english has been great. You need to keep this simple and work up to the right prop with better numbers.


1)- make sure your tachometer is correct - it needs to be compared with a shop tachometer.

2)- to be more accurate on your speeds you should use a GPS App on a cellphone to get real speeds. AChris recommends this app: GPStest.