P18 peformance

stevie wonder · 21-03-2005, 11:06 AM

Hi guys!!
I have a stonking Phantom 18 with a race tuned 2.0 litre v6 mariner 150 hp. I am currently running a Laser II 24" prop and its topping out at 72 mph, our friends have a phantom 20 with a Yamaha 225 [3.1 litre HPDI v6!] and they cant keep up above 20 mph. Does anyone have any advice on how I could improve the performance further, different prop? jack plate? I have considered a Optimax 225 but they weigh nearly 80 kgs more than the present engine and i fear this may upset the balance. How good are the 2.5efi engines? and whats the most HP I could get out of one?

Captain Chaos · 21-03-2005, 11:17 AM

feck it, @ 70mph, why change it?

stevie wonder · 21-03-2005, 11:31 AM

It feels so stable , and Im sure I could top 90mph with a big single o/b, ive seen some of the later Johnson GT 300's [4.0 litre versions] and their nice, but they weigh the same as the boat!!!

The boat used to be raced and the hull has been extencively reinforced, it used to run two of these v6 mariners and they could get well into the 100's with it. However at moment it is nice and subtle, and more than able of upsetting people round the south coast!!

So you reckon not to bother with anymore mods then?

Matt · 21-03-2005, 11:45 AM

Just out of interest, what's the gearbox ratio, (1.87:1 or 2:1) and how many rev's is the engine running flat out?

stevie wonder · 21-03-2005, 11:47 AM

1.87:1 and anything up to 6200rpm

Matt · 21-03-2005, 11:52 AM

How did you arrive at the 72mph figure?

stevie wonder · 21-03-2005, 11:55 AM

GPS

Matt · 21-03-2005, 11:57 AM

On the sea?

stevie wonder · 21-03-2005, 12:03 PM

No, the sea is normally too rough for such a light boat at that speed, the most Ive had on the sea is 64mph, i dont have trim tabs yet and it bounces around a little too much for my likening. Windermere is the place to go for speed...well, until the end of the month...goverment ba*tar*s!!!

Hydrostream · 21-03-2005, 12:04 PM

Do you know what has been done to the engine?

stevie wonder · 21-03-2005, 12:18 PM

The oil injection system has been stripped out, its been fitted with three much bigger carbs, and the inlet and outlet ports have been extncively worked on, and different gearbox [box of a 200 hp hence the 1.87:1 ratio]. The engine output is in the region of 200-220hp now.

The engine has the same transom bracket as the 275hp and 300hp mercs, which means it has the single power trim/tilt ram which gives you alot more trim out than the normal twin ram trim set up, this might explain why we can get a bit more top end???

We've used it for skiing and with a 20" laser II we were pulling up 6 mono skiers with ease and topping out @ 62 mph @ 6200 rpm. 0 - 60 times must have been around 4 seconds at the most with the 20" prop...a proper monster!!! Im thinking of getting a second hand jack plate and a chopper prop [25"-27"] and see what that does for the performance.

Hydrostream · 21-03-2005, 12:41 PM

Get a jackplate and a water pressure guage. Fit them and start raising the engine. You will probably need more prop as the revs start to climb. Most people dont like to spin stock pistons past 7k
but thats your choice!
If your water pressure starts to drop while you are raising the engine you can plug the top set of holes or 2 on the gearbox it will stop it drawing air.

stevie wonder · 21-03-2005, 12:58 PM

Will try that!!
Already have a water psi gauge and can maintain 20-25 psi at full throttle, any ideas on where i could source a manual jack plate? A hydraulic lifter would be nice but cant be arsed to spend mega bucks on one!!

Whats the spec on your weapon? it looks a bit tasty!!!

Hydrostream · 21-03-2005, 01:51 PM

Try posting in the buy & sell section of this site, there was a 5.5" cmc for sale a while back, might still be!

Alternatively, ebay in the USA is a good place for them, it's where I get most of my parts, shipping is not too much and even cheaper if you go by surface but it will take 6 weeks.

My boat is a 18' Hydrostream V-king, with a modified 2.4 but have now got a 2.5 200 stock engine for it also. I've had it in the 70's but didn't want to push it as the transom was cracked and the floor soft. It's now under total restoration, new floor, stringers, core, transom and knees. I hope to break a ton in it this summer if all goes to plan.

Hydrostream · 21-03-2005, 01:52 PM

and these guys are good for parts in the US.

http://rickracers.com/index.php?cPat...07a7a3a587189f

Alan

stevie wonder · 21-03-2005, 02:00 PM

Cheers bud,
Best of look for the restoration and clocking the magic ton!!!

sinkunit0 · 22-03-2005, 12:50 PM

do you have low water pick ups on your gearbox?

stevie wonder · 22-03-2005, 01:17 PM

No, only the stndard set up... If raising engine proves to be beneficial I might invest in that kind of set up! Whats the low down on your 200?

Matt · 22-03-2005, 01:23 PM

Stevie, What do you want out of the boat?
It's running pretty quick, but judging by the prop you have and engine height on the transom, I would imagine it's still very usuable, easy to cruise and ski, and probably handles OK in the chop.
Are you prepared to sacrifice these for speed?

stevie wonder · 22-03-2005, 01:38 PM

At present I use the 20" laser II for skiing...occasionaly, and the 24" for cruising and high speed stuff. The attitude of the boat is exceptional on flat water at speeds of 70mph + and feel that theirs still plenty more avaliable. If I get a chopper prop [25"/27"?] and jack plate for the engine i could easily transform it from one to the other quickly and without too much expence.