1989 sea ray cuddy cabin, best prop

[Josh.officer]

Hi, my old mans boat is a 4.3 litre v6 vortec mercuriser, 175 hp sea ray 22 ft, I recently damaged the prop beyond repair and thought this was a good opportunity to get as better prop put on than the previous one, it had a 19 p mercruiser 3 blade alloy prop it would do 42 mph top and rev quite high 5 and a half thousand rpms, mercruisers guidelines say no more than 4800 thousand rpm, is my prop to small for the engine, it gets out of the water ok it's not the fastest but it's certainty not slow



Any people out there that can point me in the right direction ??

Much appreciated

 

[jestor68]

Re: 1989 sea ray cuddy cabin, best prop

Verify the accuracy of the tachometer before changing prop pitch.

With a 19 pitch prop, you should be turning about 4600 rpm @ 42 mph, assuming a 1.81 gear ratio.

A 1.62 gear ratio would call for a 17 pitch prop and achieve about the same rpm and speed.

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

Agreed verify your tach before a prop change.Perhaps borrow a shop tach.

 

[Josh.officer]

Re: 1989 sea ray cuddy cabin, best prop

I have had my brother on his jet ski beside me and we were both cursing at 25 mph seemes fairly accurate to me, but it defiantly revs to high, I want to be pushing 49-50mph and 4800 thousand revs with the leg trimmed up Ovcourse

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

When evaluating your setup if we put in crap we get out crap. You need the gps speed .Some cells have a gps or perhaps a friend.
We know the pitch 19" ( about right for the setup). gear ratio is most likely 1.81. if 42mph is accurate using normal; slip of 12% actual rpm is about 4800.
If we use 5500 rpm at 12% slip we get.48 mph If we use 42 mph it indicates 23% slip depending on the boat 12% is high normal.
So either your prop is horrible or your tach is wrong high.(very common) it is 24 years old.
There is a slim chance your coupler is slipping but you would probably be getting a burnt rubber smell.
At 5500 rpm the motor would sound like its ready to fly apart.

 

[Josh.officer]

Re: 1989 sea ray cuddy cabin, best prop

Thought it could of been a spun hub but that's not the case, yes it sounds like it's about to take off at 5500 rpms I just thought that the prop was to small for the size engine

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

How is your hole shot with the 19" prop?
By the rule of thumb 1" pitch change nets about 150 to 200 rpm change.
If your tach is accurate you would need to go up 3 or 4" in pitch to get near 4800 rpm
It would certainly kill your hole shot.Might increase top speed if the motor can turn it up to 4800.
But I doubt it could.
Note that Jestors numbers mirror some of the figures I mentioned. He didn't just pull them out of a hat.
He knows more about these things than I do.

 

[Josh.officer]

Re: 1989 sea ray cuddy cabin, best prop

holeshot is not great, could be better, can i email you a video of take off to a resonable speed for a skier???

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

delete

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

You can put the video on here so everyone can see using youtube.
Unfortunately I don't have a clue how.I think they post a link to you tube .
Check your PMs.

 

[Starcraft5834]

Re: 1989 sea ray cuddy cabin, best prop

hole shot not so good? it will get a whole lot better with a 4 blade.. a 22ft Sea Ray, probably well over 3000lbs of boat to push too.. these guys can tell you what pitch 4 blade you should consider...... heavy hulled boats do very well with 4 blades... I'm only 20ft, with a heavy cuddy, came with a 3 blade on it, put a 4 blade on it,,, BIG improvement..

 

[Josh.officer]

Re: 1989 sea ray cuddy cabin, best prop

Yes my thoughts as we'll a 4 blade would go nicely I think, will look into that future this week

 

[jestor68]

Re: 1989 sea ray cuddy cabin, best prop

I'm still waiting to hear about the accuracy of the tachometer.

It must be checked against another tachometer known to be correct; such as a dealer's shop tach.

Riding next to another craft doesn't tell you if your tach is correct.

 

[jestor68]

Re: 1989 sea ray cuddy cabin, best prop

Your boat has a dry weight of about 3500 lbs. With people/gear and 35 gals of gas, it figures to about 4300 lbs operating weight.

If you put those figures thru the Mercury prop selector, it says a 19 pitch, and says it should do 4600 rpm @ 42.3 mph. In the slip calculator, these numbers represent a 9% slip; right on for the type of boat.

So everything indicates the correct performance except the tachometer reading.

If you do anything before verifying the tachometer accuracy, you are wasting your time. Have a dealer check your tachometer.

 

[steelespike]

Re: 1989 sea ray cuddy cabin, best prop

Well that's at least the 3rd calculation that says you need to check the tach.Otherwise it appears right on to your original numbers.
As jestor says get the tach fixed/replaced before any prop change.

 

[jestor68]

Re: 1989 sea ray cuddy cabin, best prop

Let me mention that cleaning the contacts on the back of the tachometer sometimes gets it working properly again.

On a 1996 boat I have, I have to pull the connector off the tach once or twice a season and clean the pins or it tends to read high.

 

[Chris1956]

Re: 1989 sea ray cuddy cabin, best prop

That boat will never achieve 50MPH with that powerplant. I had a 4.3LX (205HP) in my '88SeaRay 19' Bowrider. I would get ~40MPH at about 4500 RPM, downhill with the wind. I ran a 21"P Rapture. I would think a 19P Turning Point Hustler would be a good choice for you, but would verify RPM and Speed, before selecting.

 

[Slip Away]

Re: 1989 sea ray cuddy cabin, best prop

Agree 100% I had a 1989 Sea Ray 22ft. cuddy (same boat, same engine) for 9 years. 42mph is even optimistic. 40mph is the best you will ever get.
19p 3 blade is correct prop for that boat/motor. If you want holeshot. Go to a 14 x 20p Michigan Wheel 4 blade Aluminum Vortex prop. Part # 992204.
It's a great prop for water sports and holeshot.

 

[Josh.officer]

Re: 1989 sea ray cuddy cabin, best prop

Ok have had the tach verified reads high am going to stick with the prop I've got, good all round prop plus I've bought a new 19 p all aluminium one and fitted it already