Top Speed? 1991 Bayliner Capri 185 w/135 HP 3.0L Mercruiser 19 Pitch

S

ScooterMcTavish

Seaman
Joined
Mar 3, 2013
Messages
62
Hi Guys,

Finally had a chance to get out on a relatively calm lake yesterday, with 3/4 full gas tank and 550 lbs of people on my new to me Bayliner.

Running at WoT, I was able to get her up to 64.9 km/h which translates to almost exactly 40 MPH.

Question is, is this about as fast as I should expect/reasonably good performance for the boat/engine combo? Or would a change to prop help get a little more top end with a few less RPMs. Tach isn't working, but I'd guess somewhere in the mid 4's at WoT just based on noise.

In other considerations, the boat is mixed use, and its hole shot isn't bad for a piggy, underpowered fibreglass runabout. Getting a tube with 350-400 lbs of people up to plane takes a bit of work, but getting a waterskier up takes no effort. I seem to have a pretty good balance right now, but welcome others thoughts as to if I could see some improvement with prop changes, such as pitch, or 3 to 4 blade.

FWIW, the carb seems to be trimmed out about as good as we could get it.
 
Fastatv

Fastatv

Petty Officer 1st Class
Joined
Sep 28, 2013
Messages
258
ScooterMcTavish said:
Hi Guys,

Finally had a chance to get out on a relatively calm lake yesterday, with 3/4 full gas tank and 550 lbs of people on my new to me Bayliner.

Running at WoT, I was able to get her up to 64.9 km/h which translates to almost exactly 40 MPH.

Question is, is this about as fast as I should expect/reasonably good performance for the boat/engine combo? Or would a change to prop help get a little more top end with a few less RPMs. Tach isn't working, but I'd guess somewhere in the mid 4's at WoT just based on noise.

In other considerations, the boat is mixed use, and its hole shot isn't bad for a piggy, underpowered fibreglass runabout. Getting a tube with 350-400 lbs of people up to plane takes a bit of work, but getting a waterskier up takes no effort. I seem to have a pretty good balance right now, but welcome others thoughts as to if I could see some improvement with prop changes, such as pitch, or 3 to 4 blade.

FWIW, the carb seems to be trimmed out about as good as we could get it.
Click to expand...
That top speed sounds about right but in order to really help you with the prop, you must have a functional tach......its the only way one can verify WOT is where it should be...or shouldn't be. I don't understand the last sentence....did you mean to say "trim"?
 
S

ScooterMcTavish

Seaman
Joined
Mar 3, 2013
Messages
62
Thanks FastAV,

Sorry, guess I have trim on my mind. We adjusted the high screw to what appears to be their optimal output at WOT, and riched up the low screw a tiny bit when it threatened to stall at idle.

Guess I'll need to see why the tach isn't working. The previous owner called it "intermittent" - so far this seems to be defined as "not working". Of note, the speedo also isn't working and the fuel gauge is very jumpy. Wondering if there is a ground issue at the dash, as the other gauges (temp, oil pressure, voltage) all seem to be working fine.

Jus to ensure I'm understanding pitch as well, if I'm running 40MPH at WOT with a 19 pitch prop yet am also at 5000 RPMs that an increase in pitch would be in order? Although this would drop my RPMs and increase my top speed, it will also affect my hole shot negatively, correct?
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
If the 5000 rpm is accurate and you want to avoid over-revving without having to watch the throttle then the next pitch up should do the trick. Theoretical top speed would increase if all is well with the numbers and engine tune,etc. Now if you tow skiers a lot you might want to leave it like that (again assuming accurate numbers) and just watch the throttling.
 
A

aerobat

Master Chief Petty Officer
Joined
Jun 1, 2011
Messages
835
a friend has a rinker 186 and gets with the merc. 3.0 63 km/h gps running alone with little fuel. your results with several people and a 3/4 tank are great if real gps measured. hull and engine seem to be in good shape
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
I do think 40mph is good, and close to about all she will do Cap'n... ;)
 
A

airshot

Rear Admiral
Joined
Jul 22, 2008
Messages
4,318
Hate to rain on your parade but 40 seems quite a bit high. If that 5000 rpm is correct your engine will not last long. You need to be 4500/4600 top rpm and use a gps for accurate speed. For longest engine life your average top running rpm needs to be 3300/3400 rpm or plan on replacing engines regularly. The 3.0 is a great engine but worked very hard in larger boats, take it easy and they will last a long time, abuse them and regular replacement will be required. My aluminum hull weighs 2000 lbs with a 3.0 and a 19" pitch and she does 34 with a GPS, I would bet your glasser weighs more but probably a more slippery hull but 40 still sounds high. Have a couple fellow boaters with same boat and theirs does not reach 40 so...watch those RPM....you may get 40 at 5000 rpm but not for long.
 
thumpar

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
I ran the slip calculator on the numbers. At 12% slip you would be running around 5000 rpm. That is too high. How did you measure speed? If it was the dream-o-meter you need to GPS it. Get the tach working too.
 
S

ScooterMcTavish

Seaman
Joined
Mar 3, 2013
Messages
62
Hi Guys,

Speed was via GPS. Going to try and get the tach back up and running this weekend.

Of note, this 3.0 is the 135 HP variant - not sure if that makes a difference when doing the slip calculations.

Regardless, the only tach I have right now is my ears - engine doesn't sound like it's being over-revved. But my ears and a buck will get you a cup of coffee.

But yes, that is WOT - appreciate the recommended cruising range airshot.
 
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