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I am looking for improvements in my top end speed. I have a…

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I am looking for improvements in my top end speed. I have a fairly heavy bow rider. Its a 1992 Baja Islander 208 with a 350 mag. I have rebuilt the engine. It has 8.5 to 1 compression and a mild cam. I have a 600 cfm marine Holley with vacuum secondaries. I have a 21 pitch Mirage stainless prop. It tops out at 61 mph. This rebuilt engine redlines at 5700 rpm's. I was wondering if I should replace the rocker arms with roller rockers. Also, I am open to any suggestions to improve top end speed.

Mechanic's Assistant: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else important you think the Marine Mechanic should know?

Yes, the engine was dynoed and showed to have 384 horsepower and around 370 torque. The boat has an Alpha Drive Gen 2. I would love to see another 5 mph.

Submitted: 8 months ago.Category: Boat
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Answered in 3 days by:
11/21/2017
Marine Mechanic: MarineService8, Marine Mechanic replied 7 months ago
MarineService8
MarineService8, Marine Mechanic
Category: Boat
Satisfied Customers: 34
Experience: Certified Mercury Outboard and Mercury Mercruiser Mechanic experience with Johnson, Evinrude, OMC, Yamaha, and Honda
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What RPM was the engine turning wide open with the 21p prop?

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Customer reply replied 7 months ago
It was running 5700 rpm which 5800 is my redline.
Marine Mechanic: MarineService8, Marine Mechanic replied 7 months ago

Your going to want to go to a 23 pitch

Tempest Plus part # 825864A47

or

Revolution 4 part # 857030A46

Would be better suited props for your application

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Customer reply replied 7 months ago
I tried a Tempest Plus in a 21 pitch but it slowed down. So, you think a 23 pitch will make the difference?
Marine Mechanic: MarineService8, Marine Mechanic replied 7 months ago

Yes a 23 pitch will drop your top end rpm and make the boat come out of the hole a little shower just a little but will improve top speed switching to a 4 blade like the revolution 4 will help to not lose as much holeshot

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