Wrong Outdrive!

[washashore]

Hello all, new to this forum. Thanks in advance for any help.

Bought a 2005 Cobalt 282 with the single screw 8.1Gi with EFI. Boat got delivered and dropped in the water before I could inspect it. Ran great for the season. No hiccups, I do think I may have hit what I now believe may have been the rev limiter as at WOT the boat shut after backing off and a quick beeping was going off. Started it up and was fine.

She performed well and I really did not notice a need for more power out of the hole or top end, although we just cruise around with the kids.

THE ISSUE: After a season of growth and laziness, I just cleaned the whole thing with On & Off to get it ready for bottom paint. When I did I noticed that the drive looked a bit more beat up than the boat. Then upon further inspection I found the tag on the Duoprop outdrive. It was hard to read due to corrosion but I could clearly make out the 1.95 gear ratio. After a bunch of research I found that the 8.1 ONLY came mated with the 1.78 gear ratio. I then pulled the prop chart from Cobalt and it seems that it has the correct props for the 1.78 gears, it has the F6's in SS.

THOUGHTS? So my question is if I keep running these what am I losing, gaining, or harming? It seems running the higher ratio will simply turn the prop slower?

Is the fix to simply install a new lower unit?

[AsLan7]

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Hey WA. Welcome to the Cobaltchat forum. So glad you found us!

If you’re satisfied with the hole shot performance and top end then why change the outdrive? Touching the rev limiter while testing an empty boat with a quarter tank is fine as you won’t hit it with a standard load. Where do you boat?

Please post pics.

Again welcome aboard mate!

[washashore]

I was actually fully loaded. Top'ed off with fuel and water and had 4 adults and a few kids in it. Was dead calm so we figured we would like to see how she did.

My concern is more of a situation of premature failure with too much torque using the higher gear ratio. Also, since I am new to the boat, I do not know what it should look like at 4500rpm as far as speed. I have plenty of top end now for cruising around Nantucket Sound but if I could get more with the right equipment, that makes sense as well.

[Big Block Power]

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Hey WA. Welcome to the Cobaltchat forum. So glad you found us!

If you’re satisfied with the hole shot performance and top end then why change the outdrive? Touching the rev limiter while testing an empty boat with a quarter tank is fine as you won’t hit it with a standard load. Where do you boat?

Please post pics.

Again welcome aboard mate!

Agree here. Is it just hitting the Rev limiter? Max rpm is 4600 rpm. You want to get to that or as close as you can. So congrats. Now your gear ratio is the same as mine. It's also the same as the 8.1gi I had also. The only diff was the gi had f7 props on it I believe. Maybe even f8 but I think it was the f7.
So if you want to bring the rpm Down just go up a pitch. But you will loose some of your hole shot which is what I wasnt happy with on my Gi engine. If you are full throttle and just hitting it I would leave it alone. Load the boat up in the heat of summer and full gas I bet you lose a few rpms and are ok. If your 3/4 throttle and hitting it then go up a pitch.

Here is a great set of f7s to buy and try. If they don't work sell them. Heck they are already cheap. I might even buy them and make a 100 bucks!
viewtopic.php?f=49&t=5020

[straubtms]

Looks like I got some help from BB selling these props to you - sounds like I did offer them too cheap!! HA! Hope they do the trick.

[Big Block Power]

Looks like I got some help from BB selling these props to you - sounds like I did offer them too cheap!! HA! Hope they do the trick.

Glad I could help. Right place right time. That honestly was a good price.
These should work out perfectly for him.

[washashore]

Thanks all. I just did the calcs and it seems that prop'ing up to the F7 will get me more in line with the factory specs. Just under them actually. If I went higher, I would have been dogging the engine it seems. Many thanks.

[Big Block Power]

Thanks all. I just did the calcs and it seems that prop'ing up to the F7 will get me more in line with the factory specs. Just under them actually. If I went higher, I would have been dogging the engine it seems. Many thanks.

I think you may lose 400 rpms with them. 2 to 400 is normal.

[washashore]

Excellent, that is what I am aiming for.

[shrfdeputy]

Excellent, that is what I am aiming for.

Where did your boat come from originally? Sometimes they gear them differently for high elevation lakes.

[washashore]

Came from New Jersey at a salt water marina. The production year on the drive does not match the boat year, thus I am sure it was swapped.