kennyd

iTrader: (1)

So I have a older cig had trs drives , replaced them with shorty konrads . Also replaced the engines with 800 hp , now I'm working out the bugs and called bblades they sent me 30 p props. The props have great out of the hole power and still turn 5100 on the top end at only a 73mph top end !!! ( not happy with that mph) so this weekend I noticed no speed gain while trimming the drives and a very slight amount of bow lift ( not really any ) . So my question is it because of the short drives ??? Any ideas on why ? Do I need to add spacers to put the drives deeper in the water to gain bow lift and more speed ?

FIXX

iTrader: (2)

i would try a bigger diameter prop first and if you gain speed and bow lift then the lowers are to high..

billy boats

I'm dealing with a similar issue with my 35 sonic. I raised my drives and not gettin the speed I expected. Had BbLades lab 30 bravos for me with a lot if bow lift . They didn't help at all. I used a 1" spacer and it helped the prop slip but didn't help the bow lift . I think the problem is in the bottom of the boat. These older boats have bottoms that came out of the mold a bit wavy and then add all the years of sitting on trailers and boat lifts made them worse. At 60 mph my boat rides good, at 70 it runs a bit flat, at 80 mph the bow is low, at 85 plus it's a scarey ride with the bow plowing and bow steering . After 70mph the boat doesn't react to trim at all. It just raises rpm do to prop slip from over trimming . I tried turning the props in . I picked up 3-4 mph but then the boat felt loose and still bow steering . That makes a scarey ride at 90mph.

kennyd

iTrader: (1)

I do understand the boat hull is a problem not being a step boat , BUT with the trs drives it would gain 7-10 mph by trimming the boat .

mptrimshop

Get your bottom blue printed.

BenPerfected

Can get on plane without a major struggle? When you say the drives are raised, how far are the prop shafts below the bottom? What props have you tried? What Cig hull do you have? Also see if the last 6' of of the bottom is flat.
Brett should be able to sort this out if you give him all the info. The weight of the boat and the real in the boat HP are important.....800 HP is a bunch of power. What are the engine specs and what exhaust?

kennyd

iTrader: (1)

Gets on plane easily . 2250 rpm to get on plane , no blow out . Hull is a 85 Flatdeck 38 ft . Hp is dyno at 817 . 500 ci 871 blown 360 heads comp roller .It was dynoed with headers , in the boat are Gil with dry exhaust . 30 pitch brovos are the only ones I have tried .

kennyd

iTrader: (1)

Prop below hull . Is that at trimmed ? Or full down ?

BenPerfected

See how far the center of the prop shaft is below is below the bottom of boat. A piece of wood (6' +/-) will work to determine the flatness of the bottom and allow you to measure the prop shaft height reative to the bottom. What props are you working with and what is your target RPM range?

kennyd

iTrader: (1)

Would like the rpm to be 5100 to 5500 . I will get height Monday night . And is that at trim height or full in ?