Correct prop on 200 Mercury?

[jdupree]

Just wanted to throw this out to the prop experts.  I have the 20' CCP with a 200 Mercury.  I have not figured the speed at WOT but at around 4200 rpm's she will cruise at around 30mph according to gps.  I can push her up around 5000rpms and hit 38 to 40mph with 2 adults and a child.  Does this sound right for the motor and boat I have?  I don't know much about props or how even to figure the pitch.  I don't know if the prop is the original for the boat or not.  Just wanted to get some opinions.  Thanks.

[rsh19904]

prop is a stainless unit and I think that affects things some due to the lack of flex vs. alum.

[jdupree]

Ryan,

Are you saying the prop is stainless steel?  Looked like to me since it was painted that it was aluminum.  Anyway, plan to check the pitch.  I should be getting more top end out of the motor I think

[rsh19904]

Yeah, its a stainless.  I didn't think it was either but was told that it was by my mechanic and when he saw it there was some surface rust (looked like dirt from the lawnmower) and of course alum. won't rust so...but he said it wasn't like a mirage/venom or anything just a ho-hum stainles prop..

Not sure what the pitch was off hand or the cupping for that matter..best bet would be to take the prop off and go to the shop and show them..or get the #'s off it and try to research them with a prop co.  (michigan prop or merc. themselves)  I think WOT RPM's for that motor are around upper 5K's to around 6.  But I know what you mean..she was fast but seemed like there was a bit more to be had, espcially on the calm days..is she trimmed out Ok?

[jdupree]

Thanks for the info   I don't plan to run her over 5000rpm's.  Most of the time I have been running around 4500rpm's which yields me around 32mph all trimmed out.  That was also in windy conditions with very choppy water which of course we never got wet  Great riding hull :!:

I just feel like she could give me a little more at top end, but being a deep V not sure how much more I could get.  I will check the specs on the prop and let you know.  Props are 1 thing I know nothing about

[GoneFission]

4500 RPM and 32 MPH is about right for your setup, but you should get 5500 or so wide open and that would be about 45 MPH with your hull.  Are your numbers with the motor down, or trimmed out?  Trimming out will do more for efficiency than anything else you can do - 15% right away.  A 2.5 litre Mercury can run 5500 to 6000 RPM with no problems as long as it has either oil injection or a good 50:1 (I would perfer 40:1) fuel/oil mix.  In fact, running a while at wide open helps de-carbon the cylinders, so go at it!   :twisted:

If you are running a aluminum prop, you will get more speed with a stainless - I would guess you are running a 19 pitch now - that seems about right for your rig.  Stainless propellers have thinner with more cup on the blades due to the strength of steel versus aluminum, and are more efficient through the water.  If you are getting up on a plane with no problem, stick with a 3 blade propeller.    The 19 pitch 3-blade from Mercury is a very popular propeller and they are always on eBay:
http://cgi.ebay.com/ebaymotors/Mercury- ... dZViewItem

If you can't get over 5000 RPM trimmed out, you may have an engine problem - probably fuel-related - I would look first at the throttle cable to make sure the carbs are opening all the way when the throttle is fully open.  I've seen this a few times - the cable is incorrectly adjusted and the carburetors never fully open.  Next I would look into syncronization/timing of the carbs, followed by the possiblity of a clogged jet or two.  

Good luck and see ya on the water!

[rsh19904]

Hey Jdupree,

I know that with myself only and a good calm(flat) day I was in the creek we went out to the bay on and I hit 42 and was just about WOT but played with the trimming and man, gonefishing is right..it just jumped up on plane...I do know that neither myself or the previous owner joe had synch'd the carbs  

Hey GoneFishing..not sure if its the same person but I think I was talking to you the other day about a certain marine store in NJ where you switched motors to Merc's?  If so I got a question about my current setup I may pm you on.

[GoneFission]

Not me in Jersey last week.  Carolina maybe...

[jdupree]

I guess I need to go WOT to figure out what I have.  Looked at the prop and the numbers I have found thus far say 17-M.  That is on the outside of the prop near where the exaust comes out.  I wonder if that means 17 pitch  

Anyway, just pulled the lower unit off to replace the water pump and impeller.  Just want to make sure they are ok and I need the experience on how to do it.

If I find anymore numbers on the prop will let you guys know.  Thanks,

[rsh19904]

DUH!!   Gorgot to look at the Location on the name..

[ddd222]

jd, haven't been around in a while glad to see you are enjoying the rig. You r right on when u think u should be spinning higher. WOT should be 5500-6000 rpm, not that u should often, but more importantly to see if the boat is propped right. WOT at 5000 rpm will not hurt anything(4-700 less i'd be worried), but a correct prop in your case at 5500-6k ensures optimum efficiency in a few areas including fuel burn and excess strain planing and cruising the boat. Spinning at 5k at WOT means your plane and cruise speed rpm are skewed slightly. You mention load which assumes half full tank and 2-3 people depending on size. My guess is that your prop is off by a half inch by one parameter of the 2, and also stainless is the best way to test. If you have a decent prop guy in your area, bring your current prop, tell him the boat and say your WOT is off by 500-1k and he should be able to make u a stainless one for $175-225 dollars