CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

[shane hawkins]

Motor only reaches 4000 rpm @ wot. Timing is correct and runs smooth just seems to lag @ high rpms. 92 alpha 1 gen 2 3.0 198.R There is currently a quick silver 21p on it which ((THE PROP WIZARD RECOMMENDS)).. I have a michigan vortex 15x17 that a buddy gave me but i have to buy a hub kit to make it work.

Q: Should i go down that far to 17p and what are the ins and outs of the exchangeable hub kits? And what hub kit works with 992003 15x7 for mercruiser?

Ps. Boat seems to take forever to plane as well. We will be using the boat mainly to cruise tube and occasionally wakeboard

 

[Bondo]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Ayuh,... Obviously, the 21" is too much prop, the 17" is probably too little,...
A 19" is probably about Right...

 

[steelespike]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

While what Bondo says is right on We need more info to determine where the fault is.
Please read the stickies at the top of the page and get us as much info as possible.
Without further info with rpm "and" speed its hard to tell whats up.

 

[shane hawkins]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Everything i can tell you is that @ wot the boat does about 35 and 4000 rpm. Its a 17' glassstream ski boat. Me and my wife are the only ones typical on the boat! This boat has a quick silver stainless prop with 21 pitch. Its a alpha 1 gen 2 and gear ratio says 198r on the drive. Manufacturer says between 4400 and 4800. I have read that being closer to the top of rpms is where i should be? Also read that a single pitch change would differ about 200 rpms? I did check base timing and it was 1deg btdc.. The boat comes outta the water strong allthough it does seem to take a while to plane, but im new to boats so im learning. When the boat is trimmed correctly it seems to lag. I just dont want to spend a bunch of money on a prop if its not correct.. Again we are going to use it to ski and tube and just cruise. The boat does seem smooth @ 3000 rpms doing about 25mph.. Thanks for all inputs

 

[steelespike]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Typically a setup like that will run about 40 at 4600-4800 rpm. with a about a 21" prop,hole shot may be a little sluggish and probably not great for skiing.
Be sure the throttle plates in the carb are opening all the way.
Timing is set right and advances as it should.A compression check wouldn't hurt.
A 17" prop may turn out to be what you need for skiing and such regardless of what else you may find wrong. If the motor is running right you will need to watch the rpm.An investment in a hub for the 17 may make sense.

 

[Silvertip]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Using the 17P will likely cause an over rev. With the 21P the engine is laboring something awful so the 17P may put it "over the hump" so to speak at which point the engine can power past 4800. Try it if you wish, but I think a 19 would be about right.

 

[FFDave]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Shane,
i believe you have a glasstream 182 caravelle..right?
I thought i saw that on a previous post from you. If you do, then you have the same boat i do, and same motor. I use a 17p prop and it does it all. Im sure my speedo is off, but im right around 42mph at 4800 rpms. I was out today with 3 of my buddys,were all 180lbs to 210lbs. So i had enough weight in the boat, and using that 17p prop, still was pullin a 200lb guy out on a wakeboard with EASE. I did not feel any lag or trouble doing so.
Point im making - try a 17p or a 19p, since we have the same boat ( i believe ) you should be correct on rpms and performance with either one of those. I am going to move to a 4 blade soon though for when i have 6 people on the boat and to make it a little smoother. ( from what i hear )

Dave

 

[Shad's Searay]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

I'm sure the 19 pitch is the way to go, I got the same motor with the alpha 1,I was lookin for a change , but, after some homework on the water I can get my 17' to 42mph at 4500 rpms wot with 3 adults and 3 kids in the boat with a 13.5" 19 pitch. Just me and the wife, I can get up and move to 45/46ish mph at 4800 rpm's on a calm day .And it'll get out of the hole and pull a skier just fine. Just putting that out there.

 

[shane hawkins]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

Shane,
i believe you have a glasstream 182 caravelle..right?
I thought i saw that on a previous post from you. If you do, then you have the same boat i do, and same motor. I use a 17p prop and it does it all. Im sure my speedo is off, but im right around 42mph at 4800 rpms. I was out today with 3 of my buddys,were all 180lbs to 210lbs. So i had enough weight in the boat, and using that 17p prop, still was pullin a 200lb guy out on a wakeboard with EASE. I did not feel any lag or trouble doing so.
Point im making - try a 17p or a 19p, since we have the same boat ( i believe ) you should be correct on rpms and performance with either one of those. I am going to move to a 4 blade soon though for when i have 6 people on the boat and to make it a little smoother. ( from what i hear )

Dave

Thanks ffdave, good to see someone else with 182 caravelle. I will take ur advice and go with the 17p. The prop i have is a 15x17 is that what urs is or do you have 14x17?

 

[FFDave]

Re: CORRECTING WOT RPM ON 3.0 ALPHA ((Please help))

go with the 17p or the 19p, either one. I feel like 19p may even be a better bet for you.

Dave