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Frequently Asked Questions

Dear us engine I have a 350 marine ngine with 260 horse power and I see you state your 350 with 300 horse power uses less fuel while producing more power. The question I have is what kind of changes or modifactions do I need to do to install your 300 horse 350

300 horse 350/ 5.7 marine engine is the exact same engine castings you have now the only difference is by years. If yours is a 1996 260 horse order a 1996 with 300 horse. At US Marine engine we beef up the inside of the 260 horse 350/5.7 engine to make more horse power using much stronger higher compression pistons plus a bigger cameshaft profile also known as lift and deration and larger stainless valves. You can also use 87 octain fuel. Incease your interested we can make your 260 horse in to 350 horse 350/5.7 still all your parts bolt right on an fit in to your original engine mountings.

Question: I have a 305/5.0 in my boat now what kind of modifactions do I need to do to install a 350/5.7 I need to know will my intake manifold work, valve covers, oil pan, timing cover, exhaust manifolds and ignition work.

Yes to all your questions every part on your 305/5.0 will bolt rigt on to our 350/5.7 engines. This also includes your flywheel, harmonic balancer, power sterring, fuel system and alternator trust us to get you the right engine. I would sagest 300 horse power 350 our are the most fuel effecint.

Question: I want to up grade to more horse power will my outdrive handle more horse power.

If your original engine was a 260 horse 350 your outdrive will handle up to 350 horse power even more depends on your outdrive call us but to be safe 350 horse power no problem.

If you have a 454/7.4 your outdrive will handle up to 450 horse power and higher depends on outdrive just call but 450 is okay.

Question: I have a 1999 350/5.7 mercruiser I see you have 383 strokers 350 and 400 horse power. Can I install one of your 350 horse 383 stroker where my factory 350/5.7 was.

Yes you can install a 383 stroker in place where you have your original factory 350/5.7 without making any modifacations. We have many different 383 strokers and one of the problems is in 1986 350 changed its rear main seal to an outside one piece seal but the 383 takes a 400 crankshaft and there has never been a 400 one piece seal crankshaft from the factory. Our 383 has brand new design crankshaft that works with one piece seals this way you original flywheel will bolt right on. In the past to put a stroker in a late model 350 aplacation required replacing the flywheel, oil pan.

Question: I have a 350 with 260 horse you say in your website the 300 horse uses less fuel but has more horse power how can this be.

Your originall factory marine engine has low horse power and torque because its has low compression and has a small profile camshaft. We change the comprseeion ratio from 8.5 to 1 to 9.5 to 1 and a large camshaft profile the two together incress horse power and torque with less effert or lees throdle needed. I know this for a fact I have tested this myself and all the new engines made now of days from every manufacture build their engine with 9.5 to 1 or higher. Me I like my engines 10 to 1 ratio just use 92 octane on 10 to 1.

Question: I have a 1994 454 with 330 horse power and its a slug in the water and I cant keep fuel in it is there a way to improve on both.

Absolutely we have a 454 with 420 horse power that will use much less fuel and at the same time get you on plane much quicker. Example if your boat travels 20 knots and the rpms are 3,000 you probley have your throdle lever set over half way. With our 454 425 horse same speed same rpms but the throdle lever posistion will be under half way. My 1994 454 350 horse SEA RAY from the factory used so much fuel we did not boat much and to make thing worse I was told from the dealer I bought it from the boat would do over 55 MPH well I could never get it past 50 MPH In 1995 I took the engine out and put in high compression dome pistons to make my 454 425 horse power. Now I can go 65 MPH maybe more but my wife start yelling. Also instaed of using half a tank of fuel I now use quarter tank. You to will have similer results including your wife say slow down or let me out. My personal story call me I tell you all about it.



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