3.0 Merc Issues.

« **on:** August 04, 2009, 08:59:16 AM »

Trying to help out a buddy with a Mercruiser 3.0 I/O

He has issues getting it "over the hump" It gets out of the water ok but only gets up to about 32 MPH or so and only 2900 RPM max. I know it should do better than that on the RPM, at least around 4500 or so. Not sure about the MPH book says 42 MPH?

Has a 14.5X19 prop on it right now. Any help is appreciated.

My guess is fuel delivery?

??

« **Reply #1 on:** August 04, 2009, 10:17:08 PM »

Could be a lot of things, Not that familiar with outdrives, GT would be the pro there, and be able to tell you if its way too much prop or not for a 3.0.

Otherwise, on the engine, could be fuel issues, I'd be more beleiving an ignition issue, such as not advancing (If mech/vacuum advance and not electronic), spark scatter (bad points, incorrectly installed points), timing, etc. Then look into the fuel system. Secondaries not opening, clogged filters, bad pump.

Good luck with it Jimmy!

Ray

« **Reply #2 on:** August 05, 2009, 08:26:42 PM »

alamojimmy, the 3.0 Merc is a 130HP piece that actually for a four popper does pretty damn good...

The 19" pitch prop is a bit too tall, try a 17" pitch and run it to about 4600, they will do it all day long and twice on Sunday.

I would check the ignition and carburetor out pretty closely, the Rochester two barrels are prone to water damage in the bottom of the bowl if it has been stored for a while, unfortunately the main jets are in the very bottom of the bowl.

Good luck...BTW, if he wants to "try" a 17" inch prop, I may have one to test with...Lemmeknow.

GT

« **Reply #3 on:** August 06, 2009, 07:07:32 AM »

Last night discovered a timing issue with an advanceing problem. There is a switch that advances timing as you accelerate that you have to disable to set the "Basic Timing." Some douche bag set the timing on it while it was still advancing for the acceleration factor. Anway, it looks like he got it figured out. Testing tomorrow and I will let you know for sure.

Thanks for the Advice Ray and GT. And especially the offer to "try" a prop if needed. That is just plain awesome of you.

Thanks,

Jimmy

« **Reply #4 on:** August 10, 2009, 06:13:28 AM »

The timing fixed it. Boat jumps out of the water and hits 42.6 on the GPS in chop. I expect it will be better on glass and get what it is supposed to.

GT, He has two props that he doesn't want to use that he would like to work out a deal with you on if you are interested. He wants a spare 14.5X19. If you have one and you are interested in his two props, let me know and I will get more info on the two that he doesn't want.

alamojimmy

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