feeling a little sluggish.

[v8power]

Hi, I just purchased a 1980 Cobalt 19ft closed bow, w/mercruiser 260hp 5.7l
V8. 4bbl carb. 19p stainless 3 blade prop. Engine runs great and has plenty of power. has trim tabs, with typical gear and two peoaple around 200lbs each, it runs 45mph on the speedo, between 4700 and 5000 rpms at WOT, I know the speedo probably isnt that accurate, but my problem is, at take off it seems to be a little sluggish, the engine is making good power, but boat just seems to plane slowly, even with the trim all the way down. the trim tabs seem to help get it on plane but it still seems like it should take of a little faster. Any thoughts would be helpful, 19p seems like the right number for the rpms. but who knows? thanks for any input.

Steve

 

[steelespike]

Re: feeling a little sluggish.

It would seem to me you should be running closer to 50+ mph.
Is the bottom clean,prop in excellent shape. Is the throttle opening all the way? Have you checked the compression?
The somewhat low speed and your slow hole shot complaint may indicate something is up.You might check that all cylinders are firing.

 

[v8power]

Re: feeling a little sluggish.

the motor is runiing great, no missing or studdering, the prop is in like new condition, the throttle opens all the way, im leaning toward a timing issue, im going to try a HEI swap and get rid of the points ign. and reset the timing, it almost feels like the timing is retarded or not advanceing properly.

 

[Varago]

Re: feeling a little sluggish.

wet foam ? Sounds like your boat may be a litle heavy.


Dave

 

[ramster]

Re: feeling a little sluggish.

Check and make sure your carb is clean, and make sure that the secondaries are opening. Something is up, unless it is a super heavy boat, you should run over 50 mph with a 5.7, your rpm's are ok, but you should be turning a 21" that fast, unless you have a 1.5 gear ratio. If the engine is running smooth and idles good, I wouldn't be looking at the distributor, I dont think boats use an HEI.

 

[wca_tim]

Re: feeling a little sluggish.

Before you start changing things, check speed on gps and perhaps tach using a shop tach or even a digital timing light.

do you know specifically what kind of prop it is? just because it is a 19" pitch doesn't mean the diameter isn't too big and is making it hard for the engine to turn - wasting power that could be put into moving you forward.

Going to a vented prop (assuming you're running stock exhaust through the hub) can make a huge difference in take off (vents exhaust gas at the leading edge of the prop blades letting the prop slip, gain rpms quicker to where the engine maqkes more power. Works a bit like putting a stall converter in your street rod.

I would also weigh the boat - especially if you know of a scales near a boat ram and can take a friend with you so you can drop the boat off, go weight the trailer and then weigh the boat and trailer together. This compared to the manufacturesrs specification can give you an idea if you're carrying a bunch of extra weight.

Just some things to think about. Let us know what kind of prop you have on there now when you get a chance....

 

[v8power]

Re: feeling a little sluggish.

I think I may have figured it out. I checked the distributer and it does not have points. It has a unilite control module. But the problem was that the advance weights were stuck and not able to move. So I'm going to test it out tomorrow and see what happens.