Can't Get Above 10-12 mph

[rennen]

I have a 1957 Rockholt Utiliy Cruiser 14ft. My outboard is a 1963 40hp Evinrude selectric shift. I made my maiden voyage today! We spent a good halfhour on the water. The problem is that I can't get the boat up on the plane. Max mph is around 10 mph. I have no tachometer or speedometer as of yet, so this is an estimate. I know that my motor is sitting a little low on the transom and the cavitation plate is 3-4 inches below the hull. Is this the reason I can't get the boat up to speed? Any suggestions on how to raise the engine. <br /><br />Thanks Guys,<br />Sal

 

[JB]

Re: Can't Get Above 10-12 mph

Over-long shafts will greatly increase drag, Sal, but I don't think that much.<br /><br />I think you are running on one cylinder or have severely restricted fuel flow.<br /><br />Do some troubleshooting and give us more to work with.

 

[lark2004]

Re: Can't Get Above 10-12 mph

these old motors have a large exhaust cowling. If your cavitation is that far down, than the cowling is draging in the water below the the transom. this means huge drag! <br /><br />Raise the motor so that the cavitation plate is level with the keel.<br /><br />Also make sure you are using the correct fuel/oil mix. Yours should be 24:1 .

 

[rennen]

Re: Can't Get Above 10-12 mph

Ok,<br />I will check the spark and fuel on both cylinders. Raise the motor (using a block?), and change the fuel mix (I was running 50:1).<br /><br />What exactly is the consequence of running too lean of a fuel mixture? <br /><br />I should have also mentioned that the motor is on the lowest tilt setting. Should I raise this up a bit?<br /><br />Thanks,<br />Sal

 

[lark2004]

Re: Can't Get Above 10-12 mph

the 1963 and earlier motors ran on bronze bushes. in 1964 they moved on to bearings. If you don't run enough oil, it will overheat the bushes and sieze. <br /><br />And yes, try raising the tilt up a bit. It will help to bring the bow up and to get on the plane. if it is pushing the bow down, you just end up ploughing through the water instead of raising up on top of it. This will take a bit of playing around as each boat/motor needs to be set up slightly differently.

 

[BoatBuoy]

Re: Can't Get Above 10-12 mph

"Too lean" normally means the air:fuel ratio contains too little fuel. This can burn pistons. I think you're probably referring to the oil:fuel ratio and lark2004 is spot on.