GOTTA BE MOE SPEED....

[4lobes]

New boat owner this summer... 98 sea ray 175 with 3 ltr merc 135hr. Supper clean boat, motor purr's but....only getting 36knts at 4400rpm. I was told the boat should go 40 to 42. Hull could use a cleaning and wax. Current prop, merc 14.5 x 19. <br />Q. How accurate is rpm gage on a boat.<br />Q. Should I go to 17 or 18 pitch.<br />Q. Are 4 bladed props any better for this small engine. <br /><br />Thanks

 

[rogerwa]

Re: GOTTA BE MOE SPEED....

Are you getting 36 knots or MPH?? How much weight do you have in the boat. I have an 87 17ft searay with the 3.0 and the 19p prop and when alone I will top out around 42-43 and 4500RPM. <br /><br />With my family I'll get mid to upper 30's.<br /><br />Tach should be accurate enough..<br /><br />a 17p or 18p will drop your top end. This question all depends on how much of a load your carrying<br /><br />From what I understand a four bladedprop will improve holeshot and drop top end a little bit.

 

[drwgblanks]

Re: GOTTA BE MOE SPEED....

I have a 97 bayliner with the same engine. I can run 49 mph. It's very similar to the sea ray. On mine however, I'm running a 13 3/4x21 pitch. It's not a rocket out of the hole with a load, but she'll still get it.

 

[QC]

Re: GOTTA BE MOE SPEED....

MPL,<br /><br />My guess is that your speed is about right if you are talking knots as you noted. I also think that yuour tach is right, but it definitely could be off. When they are off thoughm, they are usually way off due to being set for a 6 or 8 cyl instead of a 4.<br /><br />How are you getting your speed numbers? Again, I think that it is about right. You're just not gonna make a lot of speed with a 135. It's about required bhp vs. available bhp. drwgblanks numbers seem high to me, but his propeller pitch backs it up somehwat. I belive that the Searay is heavier, which makes all of the difference in the world . . .

 

[drwgblanks]

Re: GOTTA BE MOE SPEED....

Quietcat, it may be a little bit heavier. I may have jumped the gun, but they sure look similar. Mine is about 2100 lbs. I checked my speed with gps. That 49-50mph is with 1 person. With people it's much less. Wonder if he is talking about knots or mph? It's hard to compare hulls and hull speeds so I don't know exactly what i was suggesting, other than maybe something he could compare to. I got a friend with an exact same Sea Ray, plus or minus a couple years. I'll ask him when I see him next what performance he gets. Moving your pitch down will only get you out of hole faster MPL, it will lower top end. Go out and throw the throttle down. Does the engine overrev over redline? If so, then get a higher pitch like a 21p. I know bayliner switched from a 13 3/4 x21 to a 14.5x19 a few years after I bought mine. I'm not sure of the performance of the newer one's. I would venture to say that the larger diameter and the smaller pitch would either be very comparable, or slow you down a bit. Waxing your hull isn't going to give you a very noticeable amount of improvement.

 

[Haut Medoc]

Re: GOTTA BE MOE SPEED....

Did you tune it up properly? I.E., Plugs, wires , Etc? Timing?.....JK

 

[Bondo]

Re: GOTTA BE MOE SPEED....

Hull could use a cleaning and wax.

That,..........And a Tune- up Might get you nearer to your Goal..............<br /><br />BTW,...36Knots is damn near 40mph........

 

[QC]

Re: GOTTA BE MOE SPEED....

Yeah, cleaning is good, but I understand that waxing the bottom can actually slow you down . . .

 

[drwgblanks]

Re: GOTTA BE MOE SPEED....

I have heard that too quietcat, unless you are talking about barnacles and a whole lot of grime. I've heard something about the beads actually causing drag. If it does indeed make it faster...I would only think it would be noticeable in a racing boat.