Need Suggestions on Prop

[Bry21317]

Ok,
So I finally took the boat out and got to really run it. With it loaded up, coolers and all that other crap, I got it up to 50.1 with GPS. This was just with me and the wife on it, for the run and all our gear.

The boat is a 94 Crownline 196BR with a 5.0 Mercruiser (2 barrel carb) and Alpha 1 drive with 1.65R gears, stated on the Lower Unit.

The guy that I purchased it from said that it would go 64, which was hard to believe with the prop that was on the boat. We did have it up to 59 for the test run, with flat water, there was not a single wave in site, as it was like 8am on a Saturday alot cooler, about 50 degrees that morning.

When I ran it yesterday, I got it up to 50.1 with the two of us and it was a bit choppy not smooth. The RPMS got up to 5200 rpm, which I think is to high for the 5.0 Mercrusier that I have.

I also had My bimini top mounted on the boat and it was up, not open, but sticking up on the supports. I also did not have the Front bow cover on front of the boat as we did in the morning that I had taken the boat for the test drive.

I could only trim to about Half Trim, or just below half, before the Prop really came loose and my rpms would shoot up.

The prop is a 21 pitch, I know, Not sure on the diameter though. I will try to find this out. It is an aluminum prop.

Does anyone have any ideas what I should have on this boat?

Thanks for all the help.

I have used the Hustler props in the past with really good results, from the Aluminum. The prop on the boat is a Michigan wheel prop, which I never really liked in the past.

Bryan

 

[andy1canada]

Re: Need Suggestions on Prop

Hey Bry...

Try going to the Mercury Marine website; propellers/prop-selector.

It'll walk you through the data entry on your boat then recommend you a prop.

Might be a good place to start.

Hope this helps.

Terry

 

[tmh]

Re: Need Suggestions on Prop

I ran your numbers thru a prop slip calc and it says you're looking at 20% slippage. This is very high, so IF numbers are all correct, then you have something dragging you down. Maybe the bimini a bit, maybe growth on hull? Or maybe something off a bit in the numbers.

Also, yes, 5200 rom is too high, don't knowexactly, but somewhere 4400-4800 is more likely recpommended max rpm range. I am surprised you are getting 5200 rpm from that set-up. A 21p prop seems about right. Have you verified the tach is correct?

What is the engine hp? I wish my 1985 5.0L could push like yours!!!!

 

[PropMD.com]

Re: Need Suggestions on Prop

are you running AL or SS? What model prop?

If you are running an AL....moving to a SS will definately help. Anything over 50 mph the aluminum slip really starts to increase.

If you are using a 21" "low profile" prop (one with a narrow blade) like a laser on that boat your slip will also go up.

More cup will also lower your slip thus giving you more top end.......assuming of course that you have the HP to turn it.

Mark.

 

[Rodsticker]

Re: Need Suggestions on Prop

I ran your numbers thru a prop slip calc and it says you're looking at 20% slippage. This is very high, so IF numbers are all correct, then you have something dragging you down. Maybe the bimini a bit, maybe growth on hull? Or maybe something off a bit in the numbers.

Also, yes, 5200 rom is too high, don't knowexactly, but somewhere 4400-4800 is more likely recpommended max rpm range. I am surprised you are getting 5200 rpm from that set-up. A 21p prop seems about right. Have you verified the tach is correct?

What is the engine hp? I wish my 1985 5.0L could push like yours!!!!

Prop slip Calc.??
Where can I find that kind of information? I would love to find out something like that for my set-up.

 

[Tredeb]

Re: Need Suggestions on Prop

Type in prop slip calculator in google

 

[Bry21317]

Re: Need Suggestions on Prop

I was on Vacation last week and missed this post had gotten some responses.

The boat is a Crownline 19 footer. It has an 8'6 beam and is a quite heavy boat. The motor does push it good though. This was with the Bimini top up but closed in the bag. It still would cause some drag.

There was alot of stuff on the boat, but at the time I had about a Half a tank of gas, which it holds 43 gallons, and the wife and myself on the boat.

The prop was definetly slipping it felt like. This is why I am wondering if I go to SS would that help? The guy I purchased the boat from said it would run low 60s with the prop that is on the boat, this is a Michigan wheel 21 pitch prop, I am not sure what the exact number is, but it is 21 pitch as it states that on the prop.

The engine is loud and very powerful, as the guy I purchased it from was a mechanic on race boats/cars. He mentioned something about a cam being in the motor, but I am not sure. It does not sound like a 5.0 when you rev it, or when its idling, but it is.

Also when I went for the test ride, before I purchased the boat back in April, the water was flat and it was in the 50s that morning. The boat ran 59 as its setup with the old owner and myself on the boat, minus the Bimini top, as I added that from my old boat. This was also with the Front bow cover on the boat, which I have not tried myself, since I purchased the boat. As the boat is plenty fast, even loaded up with 8 people on it and all our gear, I was able to get it up to 45, and thats where I quit trying but it had plenty to go, as we had 4 kids on the boat. So I didn't want to push my luck, but it will come out of the hole and the midrange power is almost Insane, how fast it will go from 25 or so up to WOT.

Hope this helps.

Bryan