OMC 5.0 Performance

[clarkmcmp]

I have a 1990 Sunbird corsair 205, OMC 5.0 Ford with 2bbl carb. I had a 19 pitch prop and am trying a 21 pitch now. At full throttle, my tach says 3000rpm, speed is 42. This is with a full tank of gas and 3.5 people on board. I have hit 45 max with a lighter load. I don't think my tach is accurate. Shouldn't I be getting closer to 50 mph? I would guess I am really around 4200 RPM. What is the best money spent to get to 50mph. I am also still using points.

This is the end of the second season with this boat. It had been sitting in a garage with a bad coil. I bought it and have been using it alot while trying to work out some bugs. I am down to a handful. Trim indicator not working, temp gauge not accurate, when I trim the engine it retards performance like something is getting grounded.

 

[Bondo]

Re: OMC 5.0 Performance

At full throttle, my tach says 3000rpm,

When you get that # to 4600rpms,........ That'll be the Prop you Need.......

 

[clarkmcmp]

Re: OMC 5.0 Performance

there is no way I am turning less than 4000 rpm now if my speedo is even close to accurate is there? How can I get a more accurate RPM reading?

 

[clarkmcmp]

Re: OMC 5.0 Performance

Maybe everyone is out with their boats and not looking at a computer screen this morning.

 

[Bondo]

Re: OMC 5.0 Performance

How can I get a more accurate RPM reading?

Ahhhhhhhh,........
Repair or Replace the Tach maybe,.......................

 

[180shabah]

Re: OMC 5.0 Performance

.....when I trim the engine it retards performance like something is getting grounded.

Start at the battery, take apart all connections, clean and reattatch. if terminals are bad, replace them.

DON'T forget the grounds.

 

[wire2]

Re: OMC 5.0 Performance

Borrow a dwell meter from a mechanic, compare the rpm on it to your tach. Then at least you'll know how far off yours is.

Is your speedo the pitot tube/water pressure type? Borrow a GPS to compare that.

 

[Bt Doctur]

Re: OMC 5.0 Performance

5.0 is a 302. lucky to get 190hp out of it.
50+ kinda doubt it

 

[180shabah]

Re: OMC 5.0 Performance

Time for a 4bbl upgrade

 

[Bt Doctur]

Re: OMC 5.0 Performance

plugged the values in and got this
3000rpm, 1.50 gear ratio, 19P ,prop slip .27736 = theor. 35mph

 

[murphini]

Re: OMC 5.0 Performance

I have 89 OMC 5.0/302 Ford 2bbl, can't remember which prop--stainless steel--and I get maybe 46mph at 4400rpm with my GPS. To my taste, that's PLENTY FAST on a 20' boat. I'm more concerned with speed from 0-22 than 45-50 though as I'm always pulling kids on tubes or wakeboards