Looking to purchase 360 with Volvo Penta 8.1 GXI

[Dropout]

Looking to purchase 360 with twin Volvo 8.1 GXI. Went for sea trial all looked good reached maxed RPM, all gauges checked, good oil pressure etc. 300 hours

I noticed when at the slip with both motors idled they were pretty shakey, like they were rocking not steady. Make sense?

All maintenance items up to date and fresh tune up.

Is this normal for these motors?

[Holy Smokes]

That should not be happening. I'd definitely mention that to the shop to investigate when they complete the mechanical inspection.

My mechanical inspection included: compression test (may as well replace the plugs), drive inspection (may as well do a full drive service), then operate & test all systems (genset, water system, sanitary system, AC/Heat, etc.)

[AsLan7]

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

I totally agree with HS. Those baby’s s should purr. ECU scan will help diagnose.

Any pics?

Again welcome aboard mate!

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[Big Block Power]

I can tell you mine is not smooth. Very rough and you think that it will actually stall.
Normal. 1st one is a bit off idle on purpose. My 8.1gi was Perfectly smooth. Totally diff cam in the gxi.
I might have the injectors cleaned this coming off season too see if it changes next year but I don't think it will. It's just a beast. As soon as you give it throttle she comes to life and no hesitation. You can feel the little surge at times if your paying attention. I even had the ecu retuned to try and change it and to raise the rpm 25 rpms. Still the same.

https://youtu.be/40-3gYZbXCI
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https://youtu.be/QGOH_7LhAxI
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https://youtu.be/2w7esnCv5dY
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[AsLan7]

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May be two different perspectives going on here. Your engine in that third video is smooth with no physical shaking noticed. She’s purring like a tiger.

If by shakey you mean a more aggressive sound, the gxi will definitely sound meaner over the GI at idle.
....especially with cc open.

Again there should be no physical shaking evident from the engine or outdrive.

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[Bdad4]

BBP your GXI sounds awesome! Agree with A7 it looks smooth as silk from the cockpit side but sounds rowdy and lumpy on the exhaust side...as it should be. That said I have a similar concern as OP with our new to me Merc 8.1 375...it drops so low on idle occasionally that it reminds me of my old carb'd hot rods with a vacume issue. Plan on plugs clean injectors etc and a scan this offseason to see if we can get on top of potential issues and achieve perfect tune. Now lets talk about those suspect front tires on that minivanish vehicle in Vid 2...better upgrade those before the next hardcore offramp bombing sends you in the ditch!

[Big Block Power]

BBP your GXI sounds awesome! Agree with A7 it looks smooth as silk from the cockpit side but sounds rowdy and lumpy on the exhaust side...as it should be. That said I have a similar concern as OP with our new to me Merc 8.1 375...it drops so low on idle occasionally that it reminds me of my old carb'd hot rods with a vacume issue. Plan on plugs clean injectors etc and a scan this offseason to see if we can get on top of potential issues and achieve perfect tune. Now lets talk about those suspect front tires on that minivanish vehicle in Vid 2...better upgrade those before the next hardcore offramp bombing sends you in the ditch!

Thanks. For the tire warning
It got new skin's before this last winter. All good. Lol daughters beater.

[Dropout]

I can tell you mine is not smooth. Very rough and you think that it will actually stall.
Normal. 1st one is a bit off idle on purpose. My 8.1gi was Perfectly smooth. Totally diff cam in the gxi.
I might have the injectors cleaned this coming off season too see if it changes next year but I don't think it will. It's just a beast. As soon as you give it throttle she comes to life and no hesitation. You can feel the little surge at times if your paying attention. I even had the ecu retuned to try and change it and to raise the rpm 25 rpms. Still the same.

https://youtu.be/40-3gYZbXCI
.

.
https://youtu.be/QGOH_7LhAxI
.

.
https://youtu.be/2w7esnCv5dY
.

.

I had the mechanic do a visual before getting in too deep, he knows the boat and said that's how the 8.1 GXI idles and did mention the large cam.

[WIriverrat]

I have a 360 with these engines. They do not shake at idle any more than other boat engines I have owned. I would check your motor mounts and make sure they are solid.