Diminished power with Marine Products 340

[Airkuld]

Hoping for some direction. We have a 2007 RZ2 with Marine Products 340hp, 123 hours, new to us this spring. Took it out for its shakedown cruise 3 weeks ago on Lake Courd'elaine, put 2.5 hours on it and were very pleased with power. However, yesterday on our home lake in Montana, I noticed a lack of punch on the low end. At the top end I couldn't get more than 4500 rpms out of it. At CDA I was running at 4900 rpm and still had a little more throttle left. I did not add any fuel between the CDA trip and yesterday. Nothing else had changed - same # of people, ballast, gear, etc.

Sending an e-mail to the dealer next but thought somebody out there would know just as much.

Thanks for the help!

[chpthril]

Fuel quality and or water in the fuel would be the 1st thing that jumps to mind. 2nd, what is the elevation of the home lake?

[boatwakes]

Elevation for sure, you may need to reprop as a result.

[Timmy!]

I'm going with elevation as well. Looks like Lake Coeur d'Alene is at 2,125'. What's your home lake's elevation? You do not need to reprop with the 340hp engine if you are under 6,000', it still has plenty of power. The 4,500 rpm seems a little low to me though which also indicates that you may have something else going on. I can get 4,900 out of my RZ2 with the Acme 537 at 5,400'.

[Airkuld]

Ennis Lake is at 4600' and with a fuel-injected engine I didn't think I should see any drop in output - that is supposed to be one of the advantages over carbueration, right? Is there a water/fuel separator? Can you point me in the direction of the fuel filter?


Thanks again for any input!

[Timmy!]

Oh yeah, you are definitely going to lose power! Fuel injection just adjusts the air/fuel/timing to make sure you aren't doing any harm to the engine. Unfortunately, it can't replace oxygen and less oxygen in the air means less power. Most of your power loss is probably due to the elevation. It's possible that you have something other than the Acme 537 prop so let's start there. Look at the prop and find out what you have on the boat.

Here's a HP loss calculator: http://www.wallaceracing.com/braking-hp.php

For the fuel filter, do a search and there is a good thread on how to replace the cartridge.

[bigskymudflaps]

I keep my 2007 rz2 just up the hill from you -- hebgen. I have the same motor and started with the 1235. No complaints yet. I ran it last summer with some smaller Enzo sacs for surfing. Flawless. I opened up the throttle once, got about 41mph out of it. Maybe 42. Can't remember the rpm. It was up there, around 5k. I did notice a difference in speed depending on the taps plate. It can be trimmed out a bit.

This year I'm running more ballast. Just installed a fully automated system that maxes out the rear lockers. We will see if i'm wanting another prop. Hope you fix the issues, i'd try a new prop. Always nice to have an extra one around.