Boat not responsive

[24gradyexp]

Boat is Grady White 24' Explorer weighs about 4000 plus 150 gallons of fuel. Motor is mounted on a bracket. Previous motor was Johnson 225 25" Shaft, prop was 15x17. Just mounted a 99 Mercury 250 with 30" shaft. Put motor all the way up on the highest holes. Prop is 15 1/2 x 17 Mirage II. There was not that much difference in the skeg heights between motors. Motor is in Gear but the boat barely moves @ 2000 RPM. Any Ideas? Thanks

 

[andy6374]

Re: Boat not responsive

Are you sure the prop is spinning? dumb question, i know. The prop size is fine. Has the engine been sitting for awhile, does it have good compression? EFI, OPTIMAX, CARB???<br />-andy

 

[24gradyexp]

Re: Boat not responsive

Motor sat for about a month. It's and EFI and has no problem running or reving. It supposively has 35 hours on the rebuild. I did not check compression but it's very responsive throttle wise. Brand new lower unit with 1:75 ratio. If I put the motor in gear it is locked, forward and reverse. It spun when I put it in gear out of the water. I think I need to check if it is prop is slipping. Would the extra 2 inches down make that much of a difference? I would not think so

 

[andy6374]

Re: Boat not responsive

If the prop is slipping, thats a problem, but can be fixed by your local prob shop. I am not sure if the extra 2 inches is a big deal, I would think that it is. I think boats that have a 20' transom will act like dead weight with a 25' shaft engine. Maybe some of the pros can help you with that one.

 

[24gradyexp]

Re: Boat not responsive

That is exactly how it acts. Dead in the water. but the motor is lifted up 3 1/2 inches.

 

[andy6374]

Re: Boat not responsive

so what you are saying is: it's as if you have a 26.5 inch shaft. I wouldn't think that 1.5 inches extra could add enough hydrostatic pressure as to cause your prop not to spin. <br /><br />Gee I really don't know. like I said hopefully the pros respond to this one.<br /><br />Check to see if your prop is slipping.

 

[Perfidiajoe]

Re: Boat not responsive

Is the anti-ventalation plate about even w/ the bottom of the boat.

 

[24gradyexp]

Re: Boat not responsive

It's about 2 inches below.

 

[andy6374]

Re: Boat not responsive

Spun Prop!

 

[Chris1956]

Re: Boat not responsive

Grady, Having the motor a bit deeper than it's predecessor will cause you to lose a bit of performance, say 3-5 MPH off WOT performance. Since your boat hardly moves, that is clearly not the problem. It does sound like a spun prop. Does it rev up above 2000RPM?

 

[24gradyexp]

Re: Boat not responsive

I can rev it but I didn't cause all it is doing is making the RPM's build and the boat does not move. That's what I was thinking if the motor was down further, lose a little top end. I'm borrowing a prop from a friend and even though it is a 21" pitch instead of 17, I'll see if the boat moves at least. Then if the boat moves, I'll get the prop re-hubbed and start from there. After the season I'll either convert it to 25" or jackup plate<br /><br />Thanks

 

[PuddleJumper]

Re: Boat not responsive

Mark the prop and hub with a permanent marker. Run the boat and check to see if mark on hub moved relative to prop.