Hi all
My boss just got a great condition 1999 Top Gun 38 with BDS super charger, I believe they are 596cc blocks with 3A drives, engine pic and others here http://www.dropbox.com/home/boat?pre...6_1_XLARGE.jpg

It came with 4 blade cleaver props that where 33's we had trouble at low speed with the engines stalling as soon as put in gear. the boat was used on an event that had to be used at slow speed so our mechanic swapped the props to 5 blade 31's Herings to help the stalling a little. we still have to trim up close to out of the water and give it a bit of throttle to get it going. So my question is is this normal to stall at idle with no throttle? Our mechanic played with the carbies and cleaned them said they where ok. The boat was a freshwater boat originally and we are in salt water.

We are seeing a top speed of 70mph at around 6000rpm with the 31 Herings. I would have thought it would be quicker than than that. Comments.

Crowfoot.

Link to photos doesn't work.

if those motors are putting out at least 650hp you should be seeing 75mph and up from there.

Weird both motors dies when you put them into gear. I'd say its a carb issue when load is put on the motor as it's dropped into drive but not on BOTH motors. Pitch of the prop still too big and causing too much load still?

Also, doesn't make much sense you have to trim the drives out like that, not to mention it's not good for the drives to put load on them trimmed out that far.

596 cc x 2 =1196 cc divided by 17 = 70.11 hp.....there's the problem..........whats the drive gear ratio ?

I'm not an expert but after I got mine off the dyno, I went to put them in gear at the ramp and they kept dying. I looked at the plugs and they were WHITE. obviously too lean at idle. I adjusted the idle screws at all 4 corners and that instantly cured it.

thanks for replies

Im guessing you're not in the States ??

1,200 rpm @ idle is pretty high......I think at a true 2000hp with a 1.5 gear and around a 30p prop you should be touching 80

I would guess way higher than that. Tiger with 6's and 1000's will be in the high 90's if not touching 100 propped right.

You cannot upload pics unless your willing to pay for a membership. You can link to pics by using a 3rd party site

yeah that's right in Australia the boat came from Canada across from Detroit from Tres. what gave it away

links don't work until 10 posts aparently.

yeah I would have thought 90 would be a closer figure.
thanks for info on idle.

can I ask what size fuel tanks a 99 topgun would have.

it drank over 200 gallons when it was filled but we have no idea what was in it previously as gauges and sender's might need replacing. that 70mph was done on full tanks with 3 passengers. it's has full cabin and we running 98ron gas.