w o t ?? what should it be at on a 3.0

[alilley]

1988 mercruiser 3.0 with an alpha 1 my wot rpm is 3800 is this to low?? it is in a 17ft tri hull design deck boat and i do not know for sure what prop is on it. i do know it is a quick silver 3 blade satinless if that helps any. boat run up to about 22 mph (using the one on the dash sorry no gps but i am working on that) and that was with 4 adults and 2 kids (both under 75 lbs) and a small dog on board. any information would be greatly appreciated and many thanks

 

[Eric 3.7LX Alpha 1]

Re: w o t ?? what should it be at on a 3.0

4400-4800 RPM's

see #13 in link below:
http://forums.iboats.com/showthread.php?t=288430

 

[1216bandit]

Re: w o t ?? what should it be at on a 3.0

It seems like you are about 1000 rpm low....I have a 3.0 130 hp and max rpm is rated at 4800

 

[IES99]

Re: w o t ?? what should it be at on a 3.0

The pitch and diameter should be on that prop somewhere. I think you have the wrong prop, the RPMs seem too low.

 

[alilley]

Re: w o t ?? what should it be at on a 3.0

i know there are some numbers on the prop but i am not for sure what they are. i will see about getting them later tonight or tomorrow during the day some time as i am not at the house. if that is the wrong prop, and i get the correct prop for it, will that improve top end speed and hole shot?? i got to thinking about it, when i got from no wake speed to w o t it does stant the up quite a bit. i thought it took it a bit to level off. once again i am kind of new to boats, and very new to porps so any help here is greatly appreciated

 

[alilley]

Re: w o t ?? what should it be at on a 3.0

ok i got the part number off of the prop itself. but i dont know how to figure out what it is say. as mentioned earlier it is a quicksilver stainless steel prop and the # is 48-16314a4 17p and got to looking around it some more found LF on it as well. can any one tell me what i have and if it is the right prop. i did a quick google search and i cam across a sight called propmd.com. i put in my part number and it came up with
QS5052X - 14 1/2 X 17 SILVERADO as a replacement. the following link is where i get the info from.

http://www.propmd.com/pc-2597-617-qs5052x-14-12-x-17-silverado.aspx[/URL]

can some one please inform me if this is the right prop if not what elese could be causing my low w o t rpm i know it is not oil leval being to high as it was just changed and has less then 1.5 hours on it. i checked it as well ans it still looks new. now i have not checked theout drive oil level. could that be the cause? i did notice some what i am think to be dried moss from it sitting in the water to long stuck to bottom of the hull. could that be the cause? if so what can i use to cloean that off?? once again any thanks in advance for your help

 

[chomamma]

Re: w o t ?? what should it be at on a 3.0

Thats a tad small for a 3.0l. I would check your tacometer to be sure it is correct. But if so, it may appear you have other issues. Check compression and timing and let us know. Has it always been this way. Is this a new boat to you?

 

[Eric 3.7LX Alpha 1]

Re: w o t ?? what should it be at on a 3.0

can some one please inform me if this is the right prop if not what elese could be causing my low w o t rpm i know it is not oil leval being to high as it was just changed and has less then 1.5 hours on it. i checked it as well ans it still looks new. now i have not checked theout drive oil level. could that be the cause? i did notice some what i am think to be dried moss from it sitting in the water to long stuck to bottom of the hull. could that be the cause? if so what can i use to cloean that off?? once again any thanks in advance for your help

Did you check ALL the possible causes that are listed in that link I posted for you above in the 2nd post?

I Gave you a list of POSSIBLE REASONS FOR LOW WOT RPM. click on it and have a look.

 

[Searay87]

Re: w o t ?? what should it be at on a 3.0

87 mercrusier 3.0 Litre Sea Ray Seville 17BR

The nametag on my engine lists WOT @ 4200-4600 RPM. With a 4 blade prop 21" pitch I reached 4000 rpm & 42 mph. Was told the 4 blade prop would reduce the high end RPM by about 200.

 

[alilley]

Re: w o t ?? what should it be at on a 3.0

to answer the list of possiable issues i will go one by one


1. Fuel condition. Type and Octane possibly old fuel
fuels was new and i think it was 87 octane
2. Propeller pitch or diameter, damaged blades
posted what is on there in previous post
3. Restricted fuel pickup tube or anti siphon valve
i will check that over the weeken
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
oil is new and just below the full mark, still clean
5. Marine growth on hull and outdrive
there is somthing on the hull,it is dried, io am thinking it to be dried moss, i am trying to figure out how to take care of that now
6. Wrong gear ratio in outdrive
the out drive has 3.0liter engraved in it from factory
7. Restricted carburetor air intake (clogged flame arrestor)
it was left loose and not bolted tight
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
will run one over weekend-did notice air coming out of the fent tube that goes to flame arrester
10. Carburetor defective, or wrong type.
was rebuilt
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
i had every one in the bow area to keep it down, once again i am new to the trim then i had it all the way down
13. Engine Overheating
run about 150-160
14. Engine timing and ignition system operation
timing light was not working didnt get a chance to check it planned on replacing light and rechecking-- what should it beset at @6-800 rpm idle?
15. Remote control cables and linkage for proper travel to open throttle plates fully.
i will have to double check this one, once again when i get home tomorrow


i hope this helps some i have also changed the spark plugs out put bosch back it (that is what was in there) but i did notice that the plug wires at the cap had teeth on them and seem to fit loose but the cap was smooth like one for a car. now this is my first boat is it supos to be like this?? and once again many thanks

 

[Adirondack]

Re: w o t ?? what should it be at on a 3.0

The answer is pretty much an easy one. If the motor is running at optimum performance the prop is too high a pitch. You change the prop pitch to reach your optimum WOT rpm range. a general rule of thumb would be about 400 rpm's for degree of pitch. Far from exact though. Thing is you mentioned numerous people on board. You also have to decide whether this is the typical load the boat will be carrying.

As an example I have two props. A 19 pitch, and a 22. 80% of the time I run my boat alone, or if I'm lucky with the company of one other. 80% of the time I run the 22. The little 4-banger handles it well. Once a year I load up 4 other rather large beer swilling gentlemen and a buttload of camping gear, and supplies (beer and some food) and head out for a 40 mile cruise to our favorite camp/fishing ground. (we call it bachelors week even though there's not a bachelor in the bunch for a good many years) That week she runs the 19. In short there is no absolute formula for a prop. Only the variables of application.

 

[alilley]

Re: w o t ?? what should it be at on a 3.0

i still have one other question. so if everything checks out and everything is optiomal leval, that winds up being normal load for the boat and i do change props, will that bring the top speed up?? i know it will bring the engine r p m up but what about top speed??

i didnt start this to be a prop question i started to make sure that everything was in optiomnal level and it sound like i have some checking to do over the weekend but can any one give me information on what i can use4 to clean the hull of all that dried up gunk??

 

[Eric 3.7LX Alpha 1]

Re: w o t ?? what should it be at on a 3.0

Does your hull have paint on it now? If so a palm sander with 60 or 80 grit, and new paint.
If the boat is not kept in the water you can use topside paint. If it stays in the water there are many different kinds of antifouling paint.

If no paint on her, maybe a power wash?, but be careful which nozzle you use.

 

[alilley]

Re: w o t ?? what should it be at on a 3.0

i do not know weather it is paint or glecoat how can i tell?all i do know is it is a gray color