UPGRADE MERCURY 150efi to 200hp

[Pelagic 660]

Guys, I have a 2004 2st 150efi Mercury and am wanting to increase power, The motor looks identical to the 175 and 200 hp 2.5lt models. I have been told that it is a simple case of having the computer re-mapped. Does anyone have experience with this and does anybody know if it is as simple as re-mapping?

Trevor.

[Blackened]

G'day

I don't think it would be that easy, Same principal with the 9.9 and 15 mercs, everything looks great and measures up, but when you get the complete parts list, it's actually the size of porting that makes most of the difference.

Probably is similar in the bigger donk like yours, Have a chat with a reputable experianced merc mechanic and get a hold of a parts list for both engines. Compare from there.

Ask yourself this, is your engine set up correctly for height and prop? As you all ready know, these are two big factors in performance

Dave

[chop duster]

Haven't heard of the conversion, although, blackend's comparison is true, although we are looking at modern EFI engines here.
Put it this way, the difference between a 200 verado and the 275 is the computer.

[Pelagic 660]

Thanks for the comments guys, I have spoken with an outboard mechanic today and his thoughts are that the computer will need to be changed which will be at considerable cost (prob not worth it). I have been playing around with motor height and propping as aresult of getting some great advice by a fellow Ausfisher, thanks Scott!;). I have managed to improve the low to midrange performance greatly but the boat seems to be hitting a wall at the top end and I was hoping for a relatively easy way to push past this point. Gone from a 17p mirage plus to a 19p mirage plus. Max rpm has gone from 6100 to 5500 and top speed has remained 35-36kn. Cruise is the winner as I have gone from 24kn at 4000 to 24kn at 3800. Still got a bit of playing around to get the revs up to 5750(max as stated), but it is a good learning excercise.

Trevor

[HH565L]

I'm no prop expert but with such a large drop in your RPMs I would guess that your outboard is labouring a little with the 19" prop.

As a guide, take a look at the serial number plate on your outboard (usually on the transom bracket somewhere) and it should also provide max RPM at WOT. Then try different prop sizes & pitches with the aim of achieving that stated on the plate. The 6100RPM you were getting with the 17" prop sounds high. Eg, Max RPM for my 200EFI Merc is listed at 5800 so 5750 sounds about right.

Another thing you might want to consider if you haven't already done so, is to adjust motor height. I have my cav plate approx 1.5 to 2" above the bottom of the hull and have found that I get the best overall performance at that height. That will vary from boat to boat so some experimentation is needed.

I am also running a 19" prop on mine and have recorded 87km/hr on the GPS at 5300RPM. It will spin to around 5800 but I've been too busy hanging on and haven't taken note of speed at those revs.

Also keep in mind 'hull speed' which is a design parameter of the hull. Once you reach that, it doesn't matter what you with your prop or how much additional hp you throw at it, any increases in speed will be minimal.

Regards,
Spiro

[OPTI]

the exhaust tuner are different between the 150 and 200,the 150 has a long tuner for better low end the 200 has a short tuner for top end,id swap the tuners and disconnect the air temp sensor,which will allow it to run 10% richer,you could send your ecu to rapair in the us and get it remaped or trade it for a 200 ecu.the tuner will fix you top end problem.8-)

[chop duster]

Pelagic,
what are you after? an economical cruise speed or flat out top end? yer you have stepped up the prop pitch 2 inches to achieve a faster cruise at a given rpm, this doesn't necessarily mean your fuel economy at this speed is going to be any better. As HH565L has touched on, the engine is most likely under more load, intern upping fuel consumption, there is a sweet spot taking load and rpm into account, although can be hard to determine unless a fuel flow meter is fitted.
If it were me, I would take the next step of investing in a fuel flow meter, otherwise its all a guessing game regarding fuel economy.
If all out top speed is your caper, wack a laser 11, or a tempest plus, or maybe ven try the enertia, seems to work wonders on some single outboard boats.

[Pelagic 660]

Thanks for the posts guys,
Basically I am playing around with the variables to get the best out of what I have, fuel is a consideration(fuel flow meter will follow soon). Top speed not so important as there are not many situations I open it right up, that said I would like the boat to perform the best that it can and the 150 does give me good down low but drops of near the topend. I got to fitting the 19 from doing some trials and recording revs vers speed and ended up with a % off slip. This was worked out for me and a 19p was reccomended. I also sent this data off to a couple of prop shops and all 3 responses were the same, or very close to it. The 19p has reduced my slip at cruise. The next step for me is to tip the prop and I will post my results. That tuner might be the shot too, however I got to balance whether it is worth the outlay or do I bite the bullet and by a new 200hp 4st or di2st?
I have raised the motor and it certainly made a huge diff to getting on the plane and holding it. It is amazing the diff a couple of centimetres will make.
Maybe I have too much time on my hands!

Trevor

[Seahorse]

u definately need to be closer to the water.

greg

[Pelagic 660]

u definately need to be closer to the water.

greg

Probably would give me something else to do