faster 1150?

[gregtobin]

After reading posts from various boaters (pulling skiers out of the hole like a rocket with an 85hp, a 150 hp going 62 mph, etc) I'm thinking that my boat is pretty slow. This is a 1976 1150 on a 1979 Glassmaster 17'6" fiberglass boat.

My top speed is about 33-34 mph with 500lbs of passengers + 1200 for boat, motor, and gear (1800 lbs). I drain less than a gallon of water from the plug after 2 hours on the water. The carb appear well synched and the butterflies open all the way at WOT. Unfortunately, my tach is broken so I don't know if the motor is revving all the way, but it sounds like it may be. I put a fresh coat of laquer on the bottom. I don't have power trim and this speed was with the motor in the middle position between hole shot and top end. The motor seems to take a while to spool up and acceleration is marginal for pulling a skier up. I'm not sure whether my prop slips but will check this out next time on the water.

How fast should I be going and any suggestions (not too expensive) on getting speedier?

Thanks!
PS - went out on the Potomac for the first time this year. Boy was it crowded! Luckily, the boat performed without a glitch and I "drove" it up onto the trailer for the first time ever..... This was a very good 4th!

 

[Yepblaze]

Re: faster 1150?

My opinions................


Your boat is probably running a bit heavy.

If I were you I'd be more concerned about top RPM, timing and not lugging it under load.

My Glasspar 16 foot and 76 1150 (w/an earlier lower unit that I had to adjust prop pitch to match it's different ratio) with just me might squeeze close to 40 absolute max but most of the time tops out about 37 and a 35 MPH fast cruise is about normal.


What's most important is that the motor runs up into the 5k RPMs during wide open throttle. That tells you that the prop is pitched well.

You don't want to lug these motors.

If you plan to or pull skiers, and tubes, you may want wide open RPM closer to 6k RPM so you know it's not fighting to get going under load.

Also if you can, be sure the max ignition spark advance is set at the lower end of the recommended scale, as any pinging, or detonation will eat pistons.


Some recommend using mid or high grade octane gasoline, but if propped right and max timing advance pulled back some, you should be OK with regular unleaded.

Of course you may not set any speed records, but it sure is nice running it week after week without failure.


There are different styles of props that will effect the bite during take off. Most of the three blade Merc stuff has a Cup to the blades that helps bite in during take off (takes more power and could bog a bit if loaded heavily), where a two blade or one of the aftermarket brands with a flatter blade profile which can get the rpm's up a little more during hard pulls.

Then there is something called venting which can pick up the take off rpm's even more getting into the power band a bit more.

If you prop for max speed you are going to suffer somewhat during take off. Especially if trying to pull someone.

 

[jddenham]

Re: faster 1150?

If you are taking on that much water you probably have waterlogged foam and alot of hidden weight. Just a thought.

 

[Clams Canino]

Re: faster 1150?

And remember... DON'T run it at WOT all the time, they aren't made to do that. They cruise nice at 4200 and burn a LOT less gas.

-W

 

[gregtobin]

Re: faster 1150?

Thanks for the suggestions. My tach doesnt work and I bought a replacement. I'll try to install it this weekend as this seems to be the missing link that will help the most in figuring out props and going faster (I really want a faster hole shot, not top end).

I'm also working on buying a used tilt system which should also help.

 

[coolguy147]

Re: faster 1150?

And remember... DON'T run it at WOT all the time, they aren't made to do that. They cruise nice at 4200 and burn a LOT less gas.

-W

nothing wrong with running it wide open?

yes 3/4 compared to WOT will use a lot less gas.

 

[achris]

Re: faster 1150?

[size=+2]Two and a half year old thread..... [/size]

I would hope the guy's got it sorted by now!