150 mercury top speed

First question is are you reaching the engines designed RPM powerband? My V21 had an OMC 200 Ocean Pro with 4500-5500 rpm WOT powerband. If I recall I ran a 3x15x19 and hit 5300 RPM WOT, alone, with full fuel, Bimini deployed, and safety gear. That equates to 52 MPH, until I bottom painted the hull and then top speed dropped to 48 MPH. LOTS of things affect top speed. I do think my extra 50 HP is good for a few more MPH than you, but I do think yours is a wee bit slow. I would guess your setup, if optimized, would yield low 40's. Someone here will surely correct me if this is off base though. I don't have any direct experience with smaller motors on the "V".
 
Mine was a little slower, around 38 mph. I bought mine from a friend who owned a prop shop. At the time, we were doing a lot of diving, so he had it propped for more torque than speed. Loaded with 60 gallons of fuel,4 divers, 8 tanks and all the other stuff it takes to breath under water, it was pretty heavy. I could run it past the 5600 limit when light, but when loaded, it was perfect.

light load with the 4 stroke, 41-44 mph. fuel wise, it likes cruising bout 30-32.
 
No bottom paint. 15 x17 inch prop. No growth on bottom. I keep her on a trailer.
So 36 mph is not good? The rpm’s are in range. Under 6000 more like 5700 rpms
 
I would think 36 is on the low side of normal, so you might try a 15x19 prop if you can find one to borrow for "Testing". That should drop RPM's 200 or so and maybe get you 3-5 MPH extra. Also, think about putting the old girl of a diet. Toss everything that isn't really needed and see if that helps. Boats tend to gain weight with age, an extra do-dad here, a couple of what-knots there, do you really need that big screen TV while out at sea? I have read that they can and do absorb moisture over time and gain a little weight there too. I don't know just how much this could be affecting your situation but does your boat live outdoors like mine did?
 
It is only me and my son on her. We do carry a lot of fishing gear. But the weight is not the issue. The rpm’s are within range and with the prop I feel she runs perfect. But the top end I think should be 40 m p h. At 36 and I can’t break 40. And I hear you guys are going almost 50 I’m concerned. Not that I want to go 50 but I should if I wanted to and can not
Skycoppor. You have a V20 and what’s your top speed if you know. And what is your engine ?
 
Scroll up and have a look at my first post and that has all of my info on my boat. Next, are you the original owner? Get the serial number off the engine, if there is a number on the block get that too. Next find a Merc site where you can verify you have a 150. It would not be the first time someone swapped a 150 cowl onto a 135-115 engine. EX. My brand new Suzuki 250 V6 will straight up exchange a 300 cowl as they are identical in every way. My old OMC 200 Ocean Pro would accept a 225 cowl and no one would know. The only difference was the carbs. I hope I am wrong.
 
Assume you are trimming the motor up at speed to get the nose out of the water and increase speed? Also what were conditions, flat calm, some wind\chop etc?
 
That was running just like in my avatar, on the last 1/3 of the hull with the engine trimmed out till it cavitated, then back in till it stopped cavitating. No trim tabs on the boat. Top speed was in a protected canal, flat calm, no wind.
 
flat calm BUT. You brought up a good point. We trim the engine down and don’t touch it all day. So I hav3 to try trimming up the engine next time. My son drives my boat so I will have to tell him to trim up or I will drive my boat. And trim up so maybe that could b3 it.
 
steplift20 said:
flat calm BUT. You brought up a good point. We trim the engine down and don’t touch it all day. So I hav3 to try trimming up the engine next time. My son drives my boat so I will have to tell him to trim up or I will drive my boat. And trim up so maybe that could b3 it.
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That could be what is keeping you out of the 40's. Let us know and good luck!
 
Skycopper said:
That was running just like in my avatar, on the last 1/3 of the hull with the engine trimmed out till it cavitated, then back in till it stopped cavitating. No trim tabs on the boat. Top speed was in a protected canal, flat calm, no wind.
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LMAO almost mentioned "Like in Sky Copper's Avatar pic" :ROFLMAO:
 
I too am running a V20 without trim tabs. Haven't felt that for what I do they would be worth the cost. That doesn't stop me from thinking sometimes how nice they would be to have.

For years I rarely touched the engine trim once under weigh. That was with the Yamaha 200 HPDI. With the Suzuki I adjust trim more frequently, for efficiency, and for conditions. You can definitely get more speed and efficiency by trimming up. Be aware of how trimming up changes the dynamics of the steering. The old Pipe Dream can get to feeling kinda squirrely at high speed with the engine trimmed up.
 
Agree, at top speed I was always very gentle to the steering inputs. I always felt stable and in control, but I also felt like I could easily ruin that feeling too.

I never had trim tabs, and only wanted them when cruising the canals and all three women would gather on one side to chat and not realize the boat was listing 30 degrees to port. Very annoying.
 
I've never had them either. The only trim tabs I had was to tell people to move to one side or another. Sorry, but unfortunately somebody has to sit on the wet side of the boat!
 
I will let you guys know what the top speed is when I go out next time. I hope this weekend but if not this weekend. Next week end for sure. You know what’s funny. I hav3 a bout for over 30 years maybe going on 40 years and I know quit a bit about boating especially my V20. But I never even thought about trimming up the engine the most obvious thing. To do.
We will see
 
steplift20 said:
I will let you guys know what the top speed is when I go out next time. I hope this weekend but if not this weekend. Next week end for sure. You know what’s funny. I hav3 a bout for over 30 years maybe going on 40 years and I know quit a bit about boating especially my V20. But I never even thought about trimming up the engine the most obvious thing. To do.
We will see
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I've got the faith!
 
Update. I was out today but the bay was a little rough so we didn’t go W.O.T. But I did trim the engine up a bit and can tell there i# less of the boat in the water so in theory. She should go faster. The thing that bothers me is that. I NEVER EVEN THOUGHT OF THAT shame on me. Today my so caught a striped bass had to be 40 pounds. And he caught a keeper fluke. Me on the other hand caught one throw back fluke.
 
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