What prop and gear ratio

[MCL]

Hi

Im trying to figure out what prop to get for my glaston 199 sierra.Its 20ft cuddy cabin,im not sure about the weight.Im quessing 2500-2700pounds with engine.

Im repowering with a new 4.3 vortec with edelbrock performer intake,thunderbolt IV,edelbrock 1409 4bbl 600cfm carb,FW-cooling,v-belt,hge alum manifolds and risers.The builder estimates it will make about 235-245hp.

I spoke with a owner of the same boat with a 175hp 4.3 lx&1.81 gear ratio and he had tried various alum&ss props of different manufactures and said that the quicksilver 21 mirage(not mirage plus) was the best prop for the boat.It would go 47mph with the revs in the optimal range with 4 people on the boat.

My problem is my current alpha one gen 1 drive is with the 1.98 gear or something very close to 2:1 ratio.I know that the engine originally came with a 130hp mercruiser.I also have a lot more hp&torgue than his setup.Can I get a mirage with enough pitch for my engine and gear ratio?

I was also thinking about selling this drive and get a new sei drive(cant beat the price) with correct gear ratio,that way I can get the right gear ratio.Whats the difference in spinning a high pitch prop slow or a low pitch prop fast?I know that the 4.3 come from the factory with a 1.81 gear ratio but would it be a upgrade to use a even lower gear ratio?

I have a 19 pitch mirage plus right now,I was thinking about keeping it as spare.It would still be low if I had the 1.81 gear ratio.

 

[Kainon]

Re: What prop and gear ratio

yea.. the correct ratio for the V6 is the 1.84/1.81. I used a 1.98 on an inline 6 1.65R and used a 23p to compensate, it did change the speed/power curve a bit, I liked it but am now back to the original 1.65R with a 19p which I haven't tried yet

You can also go a 4 blade route, and I've personally used and loved the Piranha Propellers and the hubs have a lifetime warranty and decent pitch selection and If you dont like the pitch of the blades, can return the blades and they'll send a different pitch out without charging for the blades.

My nephew has a VP 305ci 270hp in a GLastron 20' uses a Piranha 4blade 24p gets 50mph and great hole shot, and can get a 15' !!! Rooster Tail. Can't do that with his stock 23p Aluminum.

I'd try the 1.98r drive you have and drop at least a good 21p on there, if not a 22p 4 Blade.

There are Prop shops and Marina's that will let you try before you buy.

The 1.84 with the same prop will give a little more top speed, but take a little longer to get there and be a little slower out of the hole, but will be a little more economical @ cruise.

 

[MCL]

Re: What prop and gear ratio

Sorry,I forgot to tell im from Finland.I hunt my props from ebay once I know what to get.I got my reconditioned mirage plus prop for 140usd.Multiply that with 4 and thats what it costs here.

I think it could turn a 25p mirage plus with the current gear ratio.But since I wont be boating this year I think Im going to get a new sei 1.81 drive and get a 23p mirage plus as main prop.That way I have a new reliable drive and can use the 19p for play and tubing.I hoping to smoke some older small block v8 with this combo.

Dunno if im going to keep the old drive as backup or sell it.Shame do,just rebuilt it today with a new shift shaft seal and oem mercruiser waterpump.

 

[Kainon]

Re: What prop and gear ratio

Well, if you know someone that can rebuild the drive, you can change the gears, you may only need to buy 1 gear ( i dont have manual in front of me ).. like I know the 1.65 uses 24T/24T, 24 on the input, 24 on the output, the gears are in the upper section.