Newbie questions? - Maxum Boat Owners Club

sunny1881 · 07-22-2014, 02:29 PM

I have just bought a 2006 1900 SR3 with a 4.3L MPI Merc Alpha One. First time out I noticed with wot it goes to 5000rpm and I get the loud beep so I back off. Why am I redlining and cant wot? Conditions on water were great as I was on big lake that wasnt busy. Does motor need adjusting? Only has 39hrs on it so I assume should be in new condition. Lastly I looked and it has Quicksilver 1916p19 3 blade prop, is this the factory prop and or correct one?

Also anybody know where to get the ladder for under swim platform mounting, it didnt come with ladder?

Thanks for any and all help.

CountryME · 07-22-2014, 05:00 PM

Sunny,
As the boat is new to you, I need to ask, what was the temperature and when was the outdrive impeller replaced last? I would suspect that your engine was running hot due to high RPMs and low cooling water flow due to the raw water impeller needing to be replaced. This is a maintenance item and should be replaced a minimum of every 3 years or more often as some members will tell you. My 2000 1900SR with a carburated 4.3 had a 23P 3 blade prop from the factory. Based on the injection in your motor, I would guess that you are under-propped. a 21P prop shoudl get you in the right WOT range.

-JP

mmwjr · 07-22-2014, 05:31 PM

sunny welcome aboard

Need some clairfication: at 5000 rpm what is the boats speed? Is the boat overheating? I do not think you said it was.

From what you said it sounds like you are saying the WOT is 5000 rpm and not in the mid 4000's as it should be, correct?

If the boats speed does not fall off at this higher rpm them the prop needs to be increased in pitch. If the boats speed drops off and the rpms shoot up them either a spum prop hub or coupler.

PS: WOT should not be used on a regular basis, it shortens the life of the engine.

sunny1881 · 07-23-2014, 05:47 AM

From what you said it sounds like you are saying the WOT is 5000 rpm and not in the mid 4000's as it should be, correct? Answer is YES

Let me see if I can clarify. It did not run hot at all as I kept an eye on it, never went over 200-210 degrees but mostly stayed below 200 for sure. Never got speed above mid to high 30's say 38 tops because it kept running up to 5000rpm and then I get the beep so I back off the throttle. My intensions are not to run it WOT all the time, this was my first time on the water in it so I was trying to run it through the paces, testing it and seeing its capabilities. But the point is I should be able to run WOT when needed and it be at mid 4000 rpm's like from the factory and not run up to 5000rpm's so quick limiting the top end, right?

The boat is new to me and I bought from a dealer so I have no idea when the impeller was last replaced if at all being it only has 40hrs on it although it is a 2006 so maybe it has been changed I dont know. I will change it every 2 years along with regular annual maintenance.

So in conclusion, sounds like you 2 believe I need to go to 21 or 23 pitch prop as that should bring down my rpm's? Where can I found out what pitch the prop was from the factory? Shouldnt I be able to switch to the factory pitch prop and be good to go basically?

sunny1881 · 07-23-2014, 06:59 AM

So I figured out that the current prop is a Quicksilver 1916p19 which is an aluminum 3 blade 14.5" x 19 pitch prop. From the factory my boat came with a SS 14", 19 pitch 4 blade prop.

So is the current Aluminum 3 blade just not cutting it giving my the high rpm's and low top speed with WOT?

mmwjr · 07-23-2014, 12:50 PM

Quote:

Originally Posted by sunny1881

From what you said it sounds like you are saying the WOT is 5000 rpm and not in the mid 4000's as it should be, correct? Answer is YES

Let me see if I can clarify. It did not run hot at all as I kept an eye on it, never went over 200-210 degrees but mostly stayed below 200 for sure. Never got speed above mid to high 30's say 38 tops because it kept running up to 5000rpm and then I get the beep so I back off the throttle. My intensions are not to run it WOT all the time, this was my first time on the water in it so I was trying to run it through the paces, testing it and seeing its capabilities. But the point is I should be able to run WOT when needed and it be at mid 4000 rpm's like from the factory and not run up to 5000rpm's so quick limiting the top end, right?

The boat is new to me and I bought from a dealer so I have no idea when the impeller was last replaced if at all being it only has 40hrs on it although it is a 2006 so maybe it has been changed I dont know. I will change it every 2 years along with regular annual maintenance.

So in conclusion, sounds like you 2 believe I need to go to 21 or 23 pitch prop as that should bring down my rpm's? Where can I found out what pitch the prop was from the factory? Shouldnt I be able to switch to the factory pitch prop and be good to go basically?

The engine is running too HOT! A boat uses a 160 t-stat and the normal high temp is 175 above that is too hot. Change the impeller now, if that does not work inspect the exhause which is water cooled and over time gets clogged.

Wrong prop may also be making the engine work to hard and heat up.

shrew · 07-23-2014, 01:57 PM

The boat is under propped. The behavior is certainly in line with being underpropped. If the stock was a SS 14 x 19, 4 blade prop, then going to a 3 blade 14.5" x 19 prop would be going in the wrong direction. You would need to add pitch going from SS to Aluminum because SS has less flex. You'd have to add pitch dropping from 4 blades to three. Run through the Merc Prop Calculator.

http://www.mercurymarine.com/propellers/prop-selector/#

sunny1881 · 07-23-2014, 06:05 PM

I called the dealer and there gonna order me a 21 pitch 3 blade, that should do the trick, correct?

I will change impeller this weekend, thanks.

CountryME · 07-23-2014, 08:42 PM

Sunny,
As you don't know the complete mechanical history on this boat, you may want to consider changing the thermostat too. A boat cooling system is open and not pressurized like a car. As such, a marine thermostat is set lower (160°F) to prevent boiling in the high temperature areas, where a car thermostat is set to 190°F and give less margin to boiling. Some people have been known to install a automotive thermostat in the boat engine leading to out of spec operating temperatures and overheating. Get a mercury marine one to know you have the right set point in addition to changing the impeller.

Let us know how it works out and remember that boat is an acronym (B.O.A.T. = Break Out Another Thousand)

-JP

CountryME · 07-23-2014, 08:50 PM

The right prop really depends on your needs. If you are doing watersports and need the hole shot, the 19P will give you that, but you will be limited on top end (as you already know). A higher pitch 3 blade will lower your WOT RPMs into the correct range, but will get slower onto plane. 4 and 5 blade props can give you the best of both worlds, but you typically need to try them out to be sure you are happy. Some places will let you try out a prop before buying. In my opinion, having a very similar boat the 21P 3 blade should be a good all around prop with both get-up and go and a decent top speed without "blowing out" (this is where the prop cavitates and looses bite, which is probably what you were experiencing). If you need the bottom end pull, you can do a presto change-o and swap to the 19P when you need it. You can also add a set of Smart Tabs to compensate for the slower on plane time. I have a set and love them.
-JP