Converting 1989 MerCruiser 4.3 to 5.7 Magnum. Using Alpha 1 Drive.

Ferdie · Friday at 8:23 PM

The new motor has exhaust risers that are set back but still don't quite reach the elbow. They fall short by about 2".
Can I use a longer heat resistant silicone hose to couple the exhaust or do I have to change the elbows. The rise is adequate

Scott06 · Friday at 8:34 PM

Ferdie said:
The new motor has exhaust risers that are set back but still don't quite reach the elbow. They fall short by about 2".
Can I use a longer heat resistant silicone hose to couple the exhaust or do I have to change the elbows. The rise is adequate

The 4.3 and v8 use different exhaust elbows in terms of angle. also if you have a riser they use longer elbows. Yes you can use exhaust hose or silicone hose to make up the difference

Ferdie · Saturday at 8:19 PM

Thanks very much for the quick reply. All the angles are good, I'll update
my couplers.

Scott Danforth · 2026-10-11T05:11:33-0600

I use 4-layer hot-side turbo hoses. The hoses are good for 500f where the rubber coupling are good for 250f

Bondo · 2026-10-11T08:27:12-0600

Ferdie said:
The new motor has exhaust risers that are set back but still don't quite reach the elbow. They fall short by about 2".
Can I use a longer heat resistant silicone hose to couple the exhaust or do I have to change the elbows. The rise is adequate

Ayuh,..... Welcome Aboard,...... The gear ratio of the original drive is all wrong, you'll need to go with a 1.50:1 to make it work,....

Converting 1989 MerCruiser 4.3 to 5.7 Magnum. Using Alpha 1 Drive.

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Scott06

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Scott Danforth

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