186BR with Mercruser 4.3 MPI prop selection.

Deadeye

This boat came with a 23 pitch High Five prop. The issue is that the engine easily over revs with this prop even withe trim all the way down. I get 47 or 48 MPH at 4800 Rpm and 3/4 throttle. What prop should I consider for best top speed?

Michael T

Something seems weird here. Do you know your drive gear ratio. I assume you have an alpha drive. IMO a 23" prop is a normal pitch for a 4.3MPI Alpha on your boat. I assume a 5 blade would drop the rpms at wot more than 3 blade oem. 48mph (if accurate) at 3/4 throttle is very fast. Normally you'd go up a couple of inches of pitch to put your rpm range right at wot but a 25" pitch prop seems crazy for a 4.3 MPI on a 186?

Deadeye

I recently had 6 adults in the boat, it would do 47 MPH and would still red line if not careful with the throttle. I think this prop just stops working at 47 or so. BTW The hole shot is great. Don't get me wrong, I am loving this boat.

212rowboat

Toss all the rules when dealing with five blades... That said, I wager you're using a 12" high five meant for the smaller gear cases, though they can be successfully attached to/on an alpha... The one you should be spinning is something like 13.25~13.5", not right at 12"... THAT makes a difference... 

Michael T

I agree with 212! A smaller diameter or a crazy change in rake or cupping is the only thing that would make sense to me from your numbers.

Deadeye

This prop came as original equipment on my Rinker 186. It's not something weird that I put on it.

mvn

My previous 4.3L Volvo couldn't spin a 22" 4-blade stainless.  There is definitely something strange with these numbers..........

Mark

Deadeye

Just to be clear, mine is a 2014 Rinker 186BR, 220HP 4.3L Fuel Injected, purchased new this year and now has 14 hours on it. I was hoping that someone would have the same (or very similar) boat and engine combination and could tell me what prop works. A 23 inch pitch does seem like a lot of prop to me too. This is far from being my first boat, not even my first sterndrive it is my first Mercruiser. I'll check the ratio and exactly which high five is it on the weekend. I have a picture of it I took with my phone at the boat dealer just before I bought it.

lightlarry

Deadeye

Lightlarry:

Thank you for the information and I'm glad to have made your acquaintance.

 I can't help but think that this combination could do over 50 with just the right prop. That being said, I have blown my boating budget for this year having just bought the boat so a new prop may not happen.

There are some small issues with my boat, I'm wondering if you have any of these too:

1. There is a hairline crack developing across the floor in front of the rear seat.
2. The exhaust riser on the port side is hitting the fiberglass rail under the sun pad, causing vibration.
3. The volt meter is not working.
   

I am in Canada eh, east of Toronto so the boating season is starting to wind down. My Rinker will be out of the water by mid October. I'm sure you will be having fun with yours when mine is covered with snow (sigh).

Deadeye

MarkB

2014 boat? Volt meter will be a warranty claim. Mine went in year 1 and was replaced by rinker for free.

Hairline cracked I would speak to dealer about. That should be under warranty as well.

grobison

 Hi Larry
I'm also from Oz, Lake Macquarie. glad I have company Down Under. From new (2015) I had the same prop as you. I am very interested how your new prop went. My 186 has bad cavitation when laden and I am hoping a new stainless steel prop will help. Looking forward to your report.
Greg

Deadeye

Greetings it's Deadeye here. I had the chance to borrow 2 props from the dealer. a 21 Vengeance and a 25 Fury. The 21 Vengeance is not enough pitch, the engine over revs just like the original 23 Hi 5. The 25 Fury is a bit too much pitch 44 to 4500 RPM fully trimmed up, very fast, over 50 MPH. I'm thinking a 24 Tempest+ or Fury should be about right. That 23 pitch Hi5 is a strange beast for sure, it acts like a 21 pitch in forward and does near nothing in reverse.
I now have the winter to consider props as my boat is put away until spring, (late April or early May here in Ontario, Canada).

lightlarry

Michael T

@Deadeye and lightlarry, out of interest what is your gear ratio? 1.81:1 ?

Deadeye

Yes, mine is 1.81:1

Deadeye

I put a Turning Point Aluminum 3 blade on the boat. It works very well considering the low price. The Part number is: 21502311. Over 50 MPH and no more over revving the engine.