top speed for 135 v-6 merc

[dutch135]

Does anybody else have a similer boat to mine, and if so what do they do for top speed? We usually don't load the boat with a lot of gear, just the necessities and passengers. I can break 50 with myself and less than half a tank of fuel. I would be interested in hearing what other SeaRay outboards do. Thanks again.<br />

 

[Spidybot]

Re: top speed for 135 v-6 merc

Please state your propeller dimensions and what rpm you reach on WOT.<br /><br />The mentioned top speed sounds close to what you can expect for your setup, but minor adjustments may improve.<br /><br />It's always a qeustion of compromise between acelleration and top end.<br /><br />If you remove as much weights as you can, trim perfectly and have best possible conditions, a 23" pitch theoretically would provide for speeds 52-55 mph.<br /><br />Check Wisdom of Propellers to learn all about it.

 

[dutch135]

Re: top speed for 135 v-6 merc

50 mph happens with the stainless 19pitch prop, at about 5200 rpm wot. I also use a 17 pitch aluminum prop for skiing, better hole shot for me and my son to get up. but that prop tops out about 45 with wot rpm of about 5800. I am just more concerned that the engine is doing somewhere close to what it should be doing. One shop told me my spark advance was advanced too far and after they set it back i lost any and all performance, so i put it back where it was! <br />a couple years ago i tried out a High 5 prop, WOW, it was awesome! but,, out of my budget.

 

[glenns]

Re: top speed for 135 v-6 merc

I have the same boat package(and same overheating problem as discussed below). 50mph with no one else on board with stock prop @5800 rpm. Great boat/motor combo. If I figure out the problem with the telltale I will keep it forever.

 

[MIKE F]

Re: top speed for 135 v-6 merc

dutch135<br />How are you determining your speed? GPS or speedometer reading ?

 

[dutch135]

Re: top speed for 135 v-6 merc

Yea yea yea,, i know what you are going to say. I say it all the time to the guys with thier snowmobiles that go 110 mph,, let's get them under the gun first! I am only using my boats speedo,, but that is all I have access to. If I am off a couple MPH I am not too worried about it, I know I am going faster when it says 50 than when it says 40!<br />

 

[JB]

Re: top speed for 135 v-6 merc

Howdy, Dutch.<br /><br />Weigh your boat, fully loaded and ready for the water (subtract the trailer weight and add passenger weight).<br /><br />Do this calculation: HP/WEIGHT , square root of that times 180.<br /><br />That is the top speed you can get with ideal prop, clean bottom and engine properly trimmed.<br /><br />It is beyond me how people claim to have the identical boat to yours when you haven't said what boat you have, except that it is a SeaRay. I have the same problem figuring out how someone can state a top speed without that info.<br /><br />Anyway, calculate your theoretical top speed. That is it. You wont get any more true speed out of your package.<br /><br />Good luck.

 

[MIKE F]

Re: top speed for 135 v-6 merc

dutch135,<br />My boat runs 48MPH by speedo or 38MPH by GPS. <br />JB my boat should run about 6MPH by your formula.

 

[dutch135]

Re: top speed for 135 v-6 merc

Mike F,, 38 by GPS sounds pretty slow! I think I'm gonna get my snowmobiling buddy to bring over his radar gun and sit in his boat while i cruise past him, like we do with the sleds on the lake. <br />It's pretty awesome seeing 8 or 10 sleds lined up , facing each other, lighting up the radar run in winter time at nite time, and watching a 700 lb snowmobile come thru them at 100+. I would like to get a true reading of the boat , it would help pulling skiiers and wakeboards. If i am only running 18 when i think i am running 26 or so,, that would be way off for running the slalom course! Also, my signature has my boat model, engine,, etc.. so it isn't hard to figure out what boat I have, if you pay attention. ;-p<br />Is it ever going to stop raining????????<br />

 

[JB]

Re: top speed for 135 v-6 merc

Hey, Mike.<br /><br />My formula works. Your math may not. <br /><br />Tell us the weight of your boat and the prop hp of your engine. I will show you why you are getting 38mph.

 

[MIKE F]

Re: top speed for 135 v-6 merc

Okay JB,<br />I'm up to 33.4MPH. <br />Boat,motor 2,710#<br />Gas 30Gal? 180#<br />2 people(big) 440#<br />115HP

 

[sag2]

Re: top speed for 135 v-6 merc

I have the same boat. 1988 seville bow rider. I used to get 52 by the spedo when new with the stock Mercury 19" prop. I had so much cavitation so I had the dealer cut the transom down two inches. That took about 5 mph off the top, but the cavitation was gone. I currently run a 17' four blade Comp Prop and get 45 tops with the GPS. I had some electrical problems a few years ago and disconnected the tach to see if that was the problem. Problem fixed but never purchased a new tach.

 

[Spidybot]

Re: top speed for 135 v-6 merc

Sag2<br /><br />My motor is standard mounted an inch or two above the keel line and the transom is nothed (like on some racing hulls). Using the standard 19" alu prop I had severe cavitaion while accellerating, trimming, turning or carrying just three people. A heavy skier could hold back the boat at WOT!<br /><br />Switched to a 23" HighFive and dropped some in hole shot (yep, could have chosen a 21") but got all the grip I could wish for and a much better top end. Comfort and cruising mpg is great too.<br /><br />I'd take a prop replacement any day before cutting my transom.

 

[MGuckin]

Re: top speed for 135 v-6 merc

I was going to stay out of this but......<br />Theoretical MPH

 

[JB]

Re: top speed for 135 v-6 merc

Hi Mike.<br /><br />I must have guessed wrong about your boats bottom shape. <br /><br />If the stern is a very shallow vee, use 200 as the hull factor. If it is flat, use 220. Your boat must be somewhere between.<br /><br />Good luck.

 

[Dhadley]

Re: top speed for 135 v-6 merc

The numbers are amazingly close if you figure the right bottom factor. I ran the numbers on a couple of my old race boats(because we know the true weights and speed). I had to use the flat bottom factor for the Allison (pad botton) and it came to 80.269. The boat always ran (on radar) 81 to 82 in a quarter mile.<br /><br />Saga2 -- I gotta agree with UU, I'd rather spend money on a decent prop than cut anything. The good news is that when you decide you want your speed back and get the right prop it's alot easier to raise an outboard than to lower it.<br /><br />Good luck!

 

[MIKE F]

Re: top speed for 135 v-6 merc

JB,<br />My boat has a 17Deg dead rise = shallow V = 200.<br />That brings me up to 37.1 ish.I'm running a stock aluminum prop, at about 4900WOT. I imagine, I could get, a few more MPH, with a stainless prop, and get WOT closer to 5,250 max rating of engine.

 

[Hooty]

Re: top speed for 135 v-6 merc

JB,<br />What factor would you guesstimate for a Molinari tunnell?<br /><br />c/6<br /><br />Hooty

 

[JB]

Re: top speed for 135 v-6 merc

Hi, Hooty.<br /><br />Sorry, I am unfamiliar with the Molinari tunnel. DHadley might have an idea.

 

[Hooty]

Re: top speed for 135 v-6 merc

How about it Dhadley. Any idea what factor to use in JB's boat speed formula for a Molinari tunnell hull?<br /><br />c/6<br /><br />Hooty