5.7L with 1.62 gears, looking for advice

[Dcmphee]

Looking for some help on what prop I should be looking at for overal good performance. My boat is a Rinker 232, 4200 pounds dry, with a non vortec 5.7 2 barrel carb, alpha 1 Gen 2 with 1.62 gears. I have ran the boat one season now, and I think I am leaving some performance on the table. I am running a 19p 4 blade solas, max RPM is around 4100 WOT, at typically 38mph ish. I spoke with a person with the same boat and prop who changed his carb to a 4 barrel and can hit upper 40?s no problem. I do plan on doing a carb swap to a 1409 this winter. Question is I know 1.62 gears are typically not in 5.7 mercs. Are the gears going to hold me back that much once I do a 4 barrel? Should I be trying a different pitch based on my gears? Motor has healthy compression across all 8 cylinders too. Thanks for your time!

 

[alldodge]

Howdy

Looks like the folks that could look up your drive ratio never showed up. They probably never saw the post. Fun Times muc Did you count the turns to determine ratio?
http://forums.iboats.com/forum/engi...s/10502017-help-with-some-merc-serial-numbers

I have the same boat and the 5.7 is barely enough to run it. If you do have a 1.62 then that is a good thing, a 1.5 would only load the motor more. You slip numbers for a 1.62 ratio is 17% and if it had 1.5 ratio it would be 23%

If you motor is healthy, then going to a 4 bbl can help a little, but that's some coin for a little bit of gain IMO. The 4 blade 19 is like a 3 blade 21, and your not reaching the upper limit of max rpm of 4400-4800 rpm. More blades on a prop have a plus and minus and each setup varies. The plus is in most cases you get more stern lift and reduce slip, but the minus is it takes more power to turn. Being at 4100 you need to reduce pitch to get your rpms up.

I would look to 3 blade 19

My 232 will run right at 60 mph with a 3 blade 21P and a 454 Bravo 1

 

[Dcmphee]

Awesome! Thanks for the reply! I actually ended up popping the top off my drive and counting the teeth on the gears to be sure since the drive is off now anyway. I was worried that the gear ratio might the reason for my lack of top end.

Compression on my motor was all between low 150?s to 160?s so I think it should turn the prop good once i get a good setup. The boat cruises good about 32 mph but never been happy with the top end, and I sometimes have to shuffle people around if I have 6 on board to get it to plane.

 

[alldodge]

There was a guy at the dock with the same model (1996) and a bravo 3 drive and it did OK but even he said he wished it had more power. The 232 is a little heavy and needs torque to get it up. Mine is a cuddy so a tad bit heavier at 4800

 

[jimmbo]

How did you determine the ratio in the lower unit?
The gear ratio is not going to limit your top end. You have a heavy boat. A higher numerical gear ratio allows you to turn a higher pitched prop than you could if you had 1.5:1 gears. The end result is similar to a lower pitch spinning faster, but props tend to be more efficient as pitch goes up. There is some power to be tapped by going with a 4bbl carb. I took the 500 cfm Holley 2bbl off my Volvo 5.7 and put on a 650 Holley Spreadbore. My engine already had a real nice 4bbl intake. Net gain was a 10% increase in RPM. The tiny primaries helped maintain holeshot with the increase in pitch needed to return to the WOT rpm range. Your biggest bang for the buck would be to replace the heads, intake, and cam with the Vortec versions.

 

[Bondo]

Ayuh,... Get the 4bbl installed, 'n tuned, then try some Wot runs,....

If it'll pull 4800 rpms at that point, it oughta be Good to go,....

The 1.65 gears are a good thing on such a heavy hull,...

If it won't pull 4800 trimmed, 'n runnin', a smaller prop might be in order,....

 

[QBhoy]

Not positive, but it?s perhaps unlikely you have a 1.62 and a 1.47 instead. Especially with your numbers...not to add that it?s unusual that a 1.62 would be paired to that engine...unless it used to have a 4.3 ?

 

[QBhoy]

Could one of the boffins confirm with a seria number ?

 

[alldodge]

The 232 is a heavy boat, mine has a 1.5 (7.4) so having a 1.65 with a 5.7 I think would be about right

 

[Dcmphee]

I Counted the drive and driven gears at the top of the out drive, 24 teeth each. From what I found online that pointed me to say I have 1.62 gears?

 

[alldodge]

I Counted the drive and driven gears at the top of the out drive, 24 teeth each. From what I found online that pointed me to say I have 1.62 gears?

Your boat isn't that old so 24 each should not be in the picture

 

[Dcmphee]

My boat has an alpha 1 Gen 2, not a bravo series, does that make a difference?

 

[alldodge]

My boat has an alpha 1 Gen 2, not a bravo series, does that make a difference?

Yep, that makes a difference, it is either 2.0 or 1.62
Need to rotate and count or count the lower gears

 

[Scott Danforth]

usually Alpha's have the gear ratio on the decal on the side of the drive.

high-altitude 5.7 boats get the 1.62 as well as the larger boats that should get a port-chop motor

 

[QBhoy]

Reason I mention is that a friend has a maxum 2300/2400 with 2 barrel carb 250hp 5.7. Thinking it would be about the same weight.
He has an alpha 1 with 1.47 I?m sure. Runs a 19? vengeance or high 5. It reaches about 4700 rpm and about 44/45 mph.
I?d just imagine that if it was a 1.62 and running a 19?, surely the RPMs would be higher than we are seeing above stated ?
Just my logic anyway.

 

[alldodge]

If your friend does have a 1.47 then the boat would be a dog coming out of the hole, the ratio is to high. Using number listed he has 23% slip at WOT

 

[Dcmphee]

Also i think my 5.7 is only rated at 210hp with the 2 barrel on it for my year. It?s a 97 with the serial number starting with OK. Front what I have seen the 4 barrels were rated 250hp for my year. Surprised it would be that much but my motor just makes more noise after about 3800rpm, I think it just needs to gulp some more air to hopefully get some more useable rpm. 250hp with a 2 barrel has to be a vortec?

 

[QBhoy]

If your friend does have a 1.47 then the boat would be a dog coming out of the hole, the ratio is to high. Using number listed he has 23% slip at WOT

It is pretty slow out the hole, but he doesn?t do water sports and rarely even has it on the plane.
He changed to the high 5 for better acceleration.
I?ve also sat next to him on the plane doing same speed and we had almost identical RPMs. Mine is a 1.47 for sure and had a 19? on at the time.
Could be wrong, but don?t think so.

 

[alldodge]

I’ve also sat next to him on the plane doing same speed and we had almost identical RPMs.

If everything is setup correctly this would be a perfect situation.

The 1.47 ratio should turn a lower pitch prop faster then a 1.62 turning one with a higher pitch. I don't remember what you ratio was so unable to check slip numbers. The high 5 has good acceleration but in a heavier boat usually looses top end due to lift and reduced diameter.

We could go further into this if OP is acceptable, but other wise I think it would be best to start another thread because this does not directly impact his question

 

[porscheguy]

Also i think my 5.7 is only rated at 210hp with the 2 barrel on it for my year. It’s a 97 with the serial number starting with OK. Front what I have seen the 4 barrels were rated 250hp for my year. Surprised it would be that much but my motor just makes more noise after about 3800rpm, I think it just needs to gulp some more air to hopefully get some more useable rpm. 250hp with a 2 barrel has to be a vortec?

Mercruiser started using vortec heads almost immediately after gm made the switch on their trucks which was in ?96. It?s possible your engine could have been leftover inventory from ?95 but I doubt it since your boat was a high production model. It?s pretty easy to determine if you?ve got vortec heads. Just look at the bolt pattern on the intake manifold. Vortec engines have two bolts at each corner of the manifold to secure it. None near the middle. It?s important to be certain because yours was made during a transitional period. It seems strange because I thought all 5.7s had 4 barrel carbs. The 5.0 was usually rated around 200-210, and the 4.3 vortec was rated 190 or 225. It also seems odd that your boat would have even been available with that little power as either an option or as standard. Then again, in theory mine had engine choices ranging from the 3.0-5.0. I?ve yet to see on with other than the 4.3.