Tune-up Help

[WanabeBoater]

What can I do to increase top end speed of my MCM350 Mercruiser..5.7L w/ Alpha one drive on a 1994 Starcraft 2010ss (20 footer). I currently am running around WOT with a four blade 14x18 pitch prop. I get around 48 to 50 mph with a full 50 gallon tank. I have given the engine a full tune up, but have not messed with the carb at all. Any help would be appreciated.

 

[jevery]

Re: Tune-up Help

50 mph doesn't sound unreasonable for your setup. I had a 2000 Bryant 21 ft with 5.7 that would run 55 on calm water. What you failed to tell us is if your in your target rpm zone at wot and do you know what top speed was when the boat was new. Does the engine seem to be running well or a little rough? The boats 13 years old now. Did you replaced spark plug wires and distributor cap at your tune up?

 

[WanabeBoater]

Re: Tune-up Help

My target WOT is 4200 thru 4600 rpm and yes I changed spark plugs, wires, distributer cap and rotor, fuel/water seperater, oil change and filter. I run 93 octane gasoline. I currently am using a 4 blade Michigan Wheel prop as my previous prop was a 3 blade prop. While running with the 3 blade prop I was able to get 56 mph, but with the 4 blade I am only getting 48 to 50. My local marina advises to go back to a 3 blade, but to use a brand called Mirage to get higher top end and still have a good hole shot. I would like to hear from long time boaters before I go and purchase a 500 stainless steel Mirage 3 blade prop.

 

[freddyray21]

Re: Tune-up Help

sounds like the three blade prop is the solution. be careful with stainless though hit something and they don't tend to give tearing up a lower unit. I run aluminum. I'm not worried about top end and I run in the river some and the aluminum will give tearing up the prop not the lower unit.

 

[JoJoBetsy]

Re: Tune-up Help

Three blade, vented, stainless steel Mirage Plus prop and you'll get what you want. 3 bladers will give you the higher top end you want at the expense of the better hole shot that a 4 blade will provide. As for prop strikes, you can get a solid or rubber hub. The rubber will not save the prop from a possible reman, but it is designed to save the driveline. Look for them online and get the best price you can. Mercury's prices are $650 plus.

As for long time boaters...aluminum all the way. It's cheaper, breaks when it hits a stump or rock, can be remaned fairly cheap, and...well, top end is not a particular concern for the most part. I have always had SS on my boats but that's because I buy my boats to do what I want them to do. I'm not a boat engineer and everything I have every heard of family runabouts/sport boats is that all the performance is in the original engineering unless you're adding oarlocks to the gunwales.

 

[Dunaruna]

Re: Tune-up Help

[colour=blue]A cheap way to sqeeze out a few more MPH is to invest in some top quality polish, for the underneath.

 

[180shabah]

Re: Tune-up Help

I currently am using a 4 blade Michigan Wheel prop as my previous prop was a 3 blade prop. While running with the 3 blade prop I was able to get 56 mph, but with the 4 blade I am only getting 48 to 50.

Seems like you are looking for an answer that you already have.

As for shopping for a new prop, try to locate a merc prop exchange dealer. They will let you "test drive" different props before you buy one.

 

[WanabeBoater]

Re: Tune-up Help

Thanks guys for the info, I did find a prop dealer in the area who will allow me to give a few of them a try.

 

[WanabeBoater]

Re: Tune-up Help

I found that the SS 3-blader is giving me the best of both worlds...thanks guys.

 

[bomar76]

Re: Tune-up Help

[colour=blue]A cheap way to sqeeze out a few more MPH is to invest in some top quality polish, for the underneath.

A method that is guaranteed to SLOW your top speed....never wax the planing pad.

 

[WanabeBoater]

Re: Tune-up Help

Bomar76, how do you figure? The smoother the surface, less the resistance...right?

 

[bomar76]

Re: Tune-up Help

Bomar76, how do you figure? The smoother the surface, less the resistance...right?

Well known in go-fast boating....most hulls are actually abraded on the running pad to promote aereation of the water as it slips past.

As for "the smoother the surface, the less the resistance"...try rubbing two very highly polished blocks of steel together...they stick. Different physics though.

Waxing the running surface remains a sure fire way to slow your boat.

 

[tmcalavy]

Re: Tune-up Help

Seaman, look at his avatar...please don't taunt him into opening the wax or no wax argument again. Engineers say the wax/polish doesn't work, those of us who actually do it disagree. Nuff said.

 

[WanabeBoater]

Re: Tune-up Help

okay, ill take the advise...but it just doesnt seem right...take for instance a bowling ball on a highly polished lane....

 

[bruceb58]

Re: Tune-up Help

Bowling lanes are oiled but that's besides the point.


Bottom line is that a clean hull will be faster than a dirty oxidized hull.

okay, ill take the advise...but it just doesnt seem right...take for instance a bowling ball on a highly polished lane....

 

[WanabeBoater]

Re: Tune-up Help

Bowling lanes being oiled would be the same as using a smooth teflon coat on the hull...or would it?

 

[WanabeBoater]

Re: Tune-up Help

Bowling lanes being oiled would be the same as using a smooth teflon coat on the hull...or would it?

 

[Reel Poor]

Re: Tune-up Help

Look at this product.

Seaslide