Thread: Planning to build a Marine 383 Stroker

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Originally Posted by 76GMC1500

Well, the OMC Cobra is also a combination over hub/through hub exhaust. It's the same drive as the current generation of Volvo SX drives.

I've got a Volvo 280T outdrive. It's got over prop exhaust. All I know about this is that it's hard to find 4-blade stainless props for it. Do the 4-blades hold the water too well at low speed without the ventillation from the over hub?

The Prestolites are bad? I have a Prestolite. What kind of problems should I be looking for? I've got a Prestolite starter, too. It's much better built than the Delco starters but doesn't have the solenoid operated Bendix gear. This isn't a problem on my boat, but hard to start boats tend to kick the Bendix out of the flywheel just as the motor is about to start. Then it dies on you again.

Nauti, how long is the boat and what is the weight? To give you an example, my boat is 21 ft long and ~3500-4000 lbs with fuel, gear, and people. I'm running a 15x19 prop and have a 1.8ish gear ratio in the drive. I wouldn't run more prop, the boat should run more than 4200. The points are suspicious, especially single points if you have them like I do.

prestolite dist are not that good for hi rpm did i say any thing about there starters ? or any thing else they make ??i am looking at something at the stand point of hi rpm i did work at a of the biggest boat yards and tune up many boats a year prestolite dist were not what i think were that good ? light point set up not as good as the mallory with the post and base to hold the points as one unit and the mallory did make heavy points.with the prestolite that is the way it is . i said they do work for low rpm but a msd or a thunder bolt is not any good? the thunder i used in two cars on the street work fine to 6500 .i would not of put the prestolite in a car for hi rpm use or boat

The 15" pitch prop is way too small. I am running a very simular boat 25 bayliner about 7k pounds with a tired 307 with only 200 hp, and a 17" pitch prop. top speed with the bottom clean is 32 mph. I am building a 383 for the boat and plan on running a 23 pitch. By my calculation I should be running 48 mph with the new motor and prop. Im sure your wondering where I will get a 23 pitch prop?? ya can buy a 21 and have it modded at any good prop shop.
There is definatly something limiting your rpm, but that really doesnt matter since you shoudnt be running in that range anyways. I've got half your hp with my 307, and a bigger prop, and am running a simular speed, that should convince you to get a bigger prop.
Lance

Originally Posted by inspectorlance

The 15" pitch prop is way too small. I am running a very simular boat 25 bayliner about 7k pounds with a tired 307 with only 200 hp, and a 17" pitch prop. top speed with the bottom clean is 32 mph. I am building a 383 for the boat and plan on running a 23 pitch. By my calculation I should be running 48 mph with the new motor and prop. Im sure your wondering where I will get a 23 pitch prop?? ya can buy a 21 and have it modded at any good prop shop.
There is definatly something limiting your rpm, but that really doesnt matter since you shoudnt be running in that range anyways. I've got half your hp with my 307, and a bigger prop, and am running a simular speed, that should convince you to get a bigger prop.
Lance

yes you are right .the 383 should get it up on plane so a bigger prop will not hurt we reprop a 22 sea-ray454 and did get so much more top end that the speed-o pickup stop working and started to chime walk bad .we pass a 39 stinger and not much of anything was in the water but the prop. when we went by them. that is what they told me