calling all prop gurus

[verbious]

Goal: a little more top

Aluminum 14.25x19 Turning point prop

Run 37mph WOT @ 4200

1988 Invader V210 cuddy cabin, Mercruiser MCM 200 (305), 200 hp.

Would a 21 pitch give me a little more top speed? And will it drop my RPM too much? I usually cruise at 3800 at about 33-34 mph.

 

[Maclin]

Re: calling all prop gurus

I am estimating the top RPM range recommended by Mercruiser for that engine is 4000-4400, so you are in the range but still a little low on the top RPM now. If all the numbers are accurate, in my opinion if the 4200 rpm is all it will do now then going up to a 21 pitch prop will lead to slower hole shot, lower top RPM at about the same top speed or even a little lower. The engine would be lugging and could eventually be damaged. The engine needs to be able to hit the top recommended RPM even if you do not run it up there, this is to be sure the engine is not lugging at the lower rpms.

 

[steelespike]

Re: calling all prop gurus

I'm not well acquainted with V8 I/Os but::
The 210 is about 3000lbs and with a light load in my opinion the boat should easily top 40 mph. and reach max rpm with the 19" prop.
I think a careful tune up with a compression test is in order. Is the timing set right and advancing as it should? What is the gear ratio.It sometimes is on the outdrive.

 

[lexer440]

Re: calling all prop gurus

I am not a prop guru I just read the thread and decided to put my 2c in. I think the rpm range should be 4400 - 4800 and maybe the prop is already overpitched. I would try maybe a 17 pitch.

My reasoning is that I have a mercruiser 305 which gives me 220hp, my wot rpm is 4800 and I get that with a 15x16 4 blade prop and my top speed is 36mph.

 

[verbious]

Re: calling all prop gurus

The prop on the boat is pretty beat up and might be why the to speed is around 37. Not sure of great ratio. A full tune is in order. The engine didn't struggle at all except for when I plugged the pickup tube. I could be hitting max rpm, the tach is a little hard to read , but I know I am in th. e 4200-4400 range and there is nothing left. I will look for the gear ratio tonight. Thanks for the replies!!! I am leaning toward a stainless 19 pitch.

 

[verbious]

Re: calling all prop gurus

I hadn't considered that my current prop might be over pitched. I think I could a 21 that I can borrow for testing purposes.

 

[jestor68]

Re: calling all prop gurus

According to my Mercruiser data base, your 1988 5.0 L (200 hp) WOT rpm range is 4000-4600 rpm. The gear ratio should be 1.7:1.

I would simply replace the "beat up" prop with a new one of the same size. This should restore the performance lost from the old prop not working as efficiently as it could. A Solas 14.5 X 19 would perform slightly better.

You are right in the middle of your recommended rpm range. The 19" pitch is the correct prop for your application.

A tune up might help a little, but you are not going to get much more from your ( tired? )1988 motor.

 

[verbious]

Re: calling all prop gurus

Thanks jestor. Sometimes I like to overthink things. This is our first boat of this size and with an I/O. I don't run the boat at wot she feels comfortable at 3700-3800. I was thinking basically what you said, but wanted to get an opinion on my thoughts. Would you go stainless or aluminum? Thanks again.

 

[theBrownskull]

Re: calling all prop gurus

If you go stainless I would drop to a 17 and try that. Depending upon the type of prop. a 19 stainless might lower the rpm's more. Try the prop. before you buy it.

 

[jestor68]

Re: calling all prop gurus

Thanks jestor. Sometimes I like to overthink things. This is our first boat of this size and with an I/O. I don't run the boat at wot she feels comfortable at 3700-3800. I was thinking basically what you said, but wanted to get an opinion on my thoughts. Would you go stainless or aluminum? Thanks again.

I do not believe that the slight gain with stainless is worth the triple cost. Solas makes some fine aluminum props that match the performance of some stainless props. I run Solas aluminum on the "family" boat.

 

[Holy Shamolee]

Re: calling all prop gurus

I just put a Piranha 4 blade prop with hydra bite on my 25' Tollycraft. --14x18
350m mercruiser with 270 HP.
It pushes this 6400lb boat through the water at just over 30mph.
I'm happy as hell with it.

 

[verbious]

Re: calling all prop gurus

After rethinking my prop situation, I have re-realized that the boat is only going to perform at a certain level and a few MPH on the top end really isn't going to make that big of a difference. I have learned over the years that modifications lead to premature failure. Realistically I will not likely run the boat at WOT, I usually cruise at 3800-3900 and it runs just fine. If I can put on a new prop that will make better use of the RPM range and throttle position that I run, then that is a bonus and what I would rather do.

Next summer may see us pulling a tube or taking 4 or 5 people down to Pittsburgh.

I've been looking at Turning Point, Solas, and Michigan Wheel Props. I have also been reading on 3 and 4 blade designs. Stainless is out, unless I find a deal on a used one.

At the moment, I am leaning towards just replacing the worn Turning Point 14.25x19 with another Turning Point 14.25x19 and buying a 14.25x17 for a spare. They seem to get great reviews, are inexpensive, and I can probably reuse my existing hub.

Thanks again for all of you input!!

 

[steelespike]

Re: calling all prop gurus

As I understand it Turningpoint changed their hub design.So you better check if you need to get a hub with the new prop.

 

[verbious]

Re: calling all prop gurus

Good call steelespike. I just looked at my prop....It has E0-LE-1419, which I assume is the model number. The TP prop that I looked at has LE-1419 in the model number, but I not want to assume that the prop will work on the hub. I will check with Turning Point to be sure.

 

[scott8058]

Re: calling all prop gurus

As if you don't have enough to consider here's my input lol, when deciding between aluminum and ss props consider where you boat. We boat on the Illinois river which is extremely shallow, we have to be on plane coming out of the marina and run through 2 ft of water half a mile to the channel. I switched to aluminum bc eventually (knock on wood) im gonna nail a log and id much rather have my prop break than tear up my drive. Plus for every 2" in pitch you go up count on losing a couple hundred rpms, i agree that a new 19 would be best for u.

 

[mohead1]

Re: calling all prop gurus

I had a thread on here for about the same deal as you.....mine is an '88 Wellcraft 210 Classic, weight is similar, w a Mercruiser 260 (5.7) and I have a Michigan Wheel aluminum on it (came with it) thats a 14 x 19. It does ok, but my motor is supposed to be between 4400-4800 rpm at the top end. It will pull to about 4200 and around low 40's on speed. I just bought a Michigan Wheel Apollo 14.25 x 17 to see if it will pull it out better on the top....i should have the prop in a few days and give it a run.....will post

 

[cyclops2]

Re: calling all prop gurus

With just 1 person in the boat & a 1/2 tank of gas. A boat should just reach peak maximum RPM perfectly trimmed out. Or just start to pulse up & down if it has rpm limiter.

If you add more people or gearthe rpm drop down safely........As it should.

I cringe when I see ANY boat overloaded OR TOWING another boat........Running at obvious hi rpms & still not planning fast enough.

My 220 hp V8 can do 54 me alone. so if I put the legal 9 people in it. 19' ............Not to good if the temperature starts to rise up.

Edit.......

Some people confuse "Maximum safe # of people " .... & WOT with any # of people the " USCG label says is safe ", as the same safe condition. They usually are not the same for the motor safe condition.

 

[jestor68]

Re: calling all prop gurus

If you order a new TP prop here, it will come with the hub kit unless you delete it. The hub kit is included in the advertised price.