max speed from a 135 black max...42mph???

[winterblues]

i have a 1990 sea ray 180 w/135 black max. it has a SS 19" quicksilver mirage prop and i can get it about 42mph tops. i have some soft spots in the floor that will be gutted and replaced soon. with a new floor and a 21" prop will i get more than 42mph?? thanks

 

[Faztbullet]

Re: max speed from a 135 black max...42mph???

From what you posted, the prop calculater puts your rpm at 5450 which is perfect. If you go up a pitch it usually drops your RPM about 500 and if it does drop the speed will not change(still 42mph)Stay with the 19...

 

[j_martin]

Re: max speed from a 135 black max...42mph???

There's a lot more to it than the prop. For starters, it's a good bet you're hauling around a fair amount of water weight. Engine height, weight distribution, trim angle, (which can be grossly affected by a wet transom) etc. Proper setup requires a tachometer. Do you even have one?

hope it helps
john

 

[sschefer]

Re: max speed from a 135 black max...42mph???

Speed is about right. 42-45 @ about 5400 RPM is, as John say's, "perfect".

Changin out the deck would only get you better performance if you we're lessening the weight by a significant amount. Roughly guessing I'd say you'd need to loose at least 100lbs before you see a single MPH gain.

I've got 3/4" decks in my boat. That's up from the original 5/8" and mine are sealed on both sides so I added weight when I replaced mine. No difference in MPH though.

 

[winterblues]

Re: max speed from a 135 black max...42mph???

yes the boat has a tachometer....i cant remember what it is for RPMS at WOT off the top of my head. i just had it serviced new water pump, t-stats housings, sparks, new temp sensors and gear oil. my roomate is a carpenter so we are going to tackle the floor this weekend. when i pull the drain plug no water is coming out which is good. however, when i start the bilge pump i can barely hear it run and it hums for a few seconds and then i dont hear it...could it be bad?? thanks all for the replies!

 

[j_martin]

Re: max speed from a 135 black max...42mph???

yes the boat has a tachometer....i cant remember what it is for RPMS at WOT off the top of my head. i just had it serviced new water pump, t-stats housings, sparks, new temp sensors and gear oil. my roomate is a carpenter so we are going to tackle the floor this weekend. when i pull the drain plug no water is coming out which is good. however, when i start the bilge pump i can barely hear it run and it hums for a few seconds and then i dont hear it...could it be bad?? thanks all for the replies!

The water weight I referred to is in saturated foam and saturated wood. It won't run out when you pull the plug.

For propping, you should select the pitch so the engine is running in the upper part of the specifiec WOT RPM range at WOT with your expected light load, ie driver and half a tank of gas. Then the speed will be the best you'll get with that setup. If you then increase the pitch of the prop, you will lose speed and damage the engine over time by overloading it. In fact, if you routinely load it up to the point that it runs below the specified range, you should lower the pitch, and throttle back slightly when you're light.

That said, how you mount your engine could have as much effect as 4 or more inches difference in prop pitch. It also effects the prop pitch needed.

hope it helps
John

 

[winterblues]

Re: max speed from a 135 black max...42mph???

thank you john. me and my roomate are going to rip out a section of the floor this sunday to see how bad it really is.

happy boatn and fishn!