STV with 200hp 2.4ltr increase MPH?

[STV_ERIK]

Looking for some assistance in my next steps. Year 2 with boat and motor. I have put bob's shallow water pick up, 28 cleaver, carbon fibre reeds, drilled out exhaust, installed tunner (bob's), velocity stacks, port-matched, re set up timing. The boat is a 18ft STV "v" nose i believe its first generation. It has a power lift with 6" set back. I can only make the boat turn 60-63mph, by all accounts the boat should run approx, 85-87mph on a good day. Motor RPM is 5600-5800.
My next steps are to lift the motor on the boat it may not be high enough? I have not filled in the hole for the oil drain plug, I was told it will rob 7-10 mph, true or false? Jetting. The motor has 84's and 82's ? Too fat? 80 deg temp? Any suggestions? Just tweeking!

[outasite]

I don't know nuttin bout an stv but those numbers sound really weak if your running the right height seems like that engine should be turning 63-6500 with that prop and 80+ mph.are you sure that the timing is right?

[tony97gt]

I have an 18' Talon that had a 200 Merc carb'd and it ran 80mph with a crappy 28p chopper prop. Something ain't right with your setup. Are you running the jackplate high enough and are you trimmed up? Not trying to insult your intelligence or experience, just that those numbers are pretty low IMO.

[Guillaume]

Something is really wrong... my 100% stock 200 hp 2.4 ran 60 mph with a turbo 21p prop in a 1200 lbs hull @ 6200 rpm.
Speed is limited by the prop I have 'cause it accelerates really really fast to 60 mph then tops out :p

With a lighter boat like yours, more prop and a modified engine you should be WAY faster than that.
Sounds like you're down on power.

What do the plugs look like? Good compression on all 6?

Is the prop running on the surface??

5800 rpm, 1.87 gears, 63 mph and 28p = 23% slip....

[Fish]

start with your engine height, i am guessing the prop is burried in the water. if you have a bobs low water pickup, you should be able to look straight along the hull from the front to the back, you should be able to just barely see the holes on the front of the bullet along the bottom of the hull. i am not as familiar with the v nose stv's, but the cleaver is a stern lifting prop, how much of your boat are you getting out of the water when you are running? Do you have a kill switch and life jacket with leg straps like a life line or SRP?

[STV_ERIK]

I believe height is the first step. Thanks to all for pointers, Power is good, compression is good, if the motor is jacked all the way up, with a strait edge and the motor trim parallel to the bottom of the boat the strait edge is not quite at the center line of the prop shaft, it is about 1/4 to 1/2 inch above the point on the nose. Will jetting make much diff at this point for RPM? What timing should I run, just set up for Stock Mercury specs? Thanks all!

[STV_ERIK]

Hey "Fish" The boat hasn't started to lift lots still in the water. I have a Kill switch but no leg strap? Why do you ask? What is SRP? What about the hole for the oil fill? does it drag enough to reduce speed?

[STV_ERIK]

Tony97gt, I appreciate the feed back no insult, this is a new toy, i have been racing snowmobiles and this is a new challenge. I agree they are low, lots of set up left, I bought the boat as a project that needed much TLC, Everything is matched properly now, motor,lower end, prop, some bolt ons etc, need to make it go now.

[vector mike]

You said you re set your timing. What did you set it to? What is your compression? Is it a stock compression motor? 82's and 84's should be fine for a basicly stock 200. The mods you have done shouldn't change the jetting that much. The stacks are the only thing that could possibly let in more air to need more fuel. I run 88's in mine. Otherwise it sounds like your propshaft is too low.

[STV_ERIK]

I looked last night, with motor up, it appears to be 1.5 to 2 inches low will that bring rpm down that much? . Motor is stock compression if i remember it was around 135 on all timing was set to merc specs, 461 deg or something like that without the book in front of me.

[STV_Keith]

First off, it sounds like your engine is WAY low. With a 6" jackplate, I run my propshaft centerline at 1-1/4" above the bottom. Start there, then try props next. Being the V bottom version, I doubt your boat generates as much bow lift as the later "inverted V" STV's like mine. I would suggest a chopper or maybe a high-rake Mazco RE. This would normally be a 26p or less RE-3, but there was a Mazco RE-3 27 for sale on here by one guy that was one of my old props. I found that it was originally built for a bass boat guy and is a high-rake 27p. You may find it in the propellers for sale section.

[STV_ERIK]

Thanks for the advice, the boat has plenty of bow lift but the motor is way to low compared to what you r talking, will it draw down rpm 600-800?

[STV_Keith]

Thanks for the advice, the boat has plenty of bow lift but the motor is way to low compared to what you r talking, will it draw down rpm 600-800?

Easy!

[Fish]

Thanks for the advice, the boat has plenty of bow lift but the motor is way to low compared to what you r talking, will it draw down rpm 600-800?

definitely.

here is a pic of my stv running, the bottom half of the bullet and only part of the prop is in the water when it is set up right. STV keith is thinking the same thing i was when i asked the question about how much of the boat was in the water and gave you some really good prop suggestions. Once you get your height right, then it is time to start dialing in your prop choice.

this is an example of a jacket with leg straps, it is a lifeline:
http://www.lifelinejackets.com/comp_jackets.cfm

these are srp:
http://www.securityrace.com/lifejackets/srplifejackets.html

the reason for the leg straps is it prevents the jacket from coming up over your head or pinning your arms if you get tossed at the speeds we run. the lifeline and srp, in addition to being designed to stay together at speeds over 100mph, also will float you face up no matter what if you are unconscious or cannot swim. stay in this sport long enough you will see people hurt, you will see people who end up even worse.


i have not seen your oil fill, but i am guessing there is not enough drag to worry about right now. i beleive your biggest issues are height first, prop second, weight distribution third. most importantly, get some seat time and get to know your boat, wear a jacket and use your kill switch.
257821

[STV_Keith]

Depending on your gearcase, you may have an oil drain plug in front of the skeg. If this plug sticks down a bit, it may be double washers or something. With everything else sealed up, you can pull the lower plug and oil shouldn't come out very much or very fast. Take a pic and make sure there is only one sealing washer on the plug. Might even want to buy a new one as the pic might destrol the old one getting it out.