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Hi Everyone,

I'm new to this forum and boat ownership. I have a 1999 20 foot Ventura that was recently repowered with a rebuilt 2006 225 HP Optimax. I've been working through a number of issues, but I have a questions that hopefully the community here can help me with.

The motor had a Mirage plus 19P that kept me at 4800 rpm and 40 mph at WOT. I switched to a Mirage plus 17P which got me to to 5200 rpm and 44 mph. Does this seem reasonable? I'm questioning whether my throttle linkage is adjusted properly, which might be keeping me from WOT. I estimate the boats loaded weight @ ~4000 lbs.

Thanks in advance!

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You are close.

WOT rpm's for the Optimax 225 is 5750.

When I run the information through the prop calculator I see 17" of pitch. Mirage 17's are installed on many Opti's so that is a good Make, model of prop.

What is the engine height of the boat? How many empty hole(s) are there above the top engine bracket bolt?

I think you should be at "2 holes up" with the bolts being in the 3rd hole counting down from the top.

If you raise the engine, for every hole, you will gain ~200 rpm's

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Thanks for the reply, Phil. It's comforting to know I'm in the right ballpark compared to real world experience. I ran through a calculator and 17P was at the lower end of the recommendation.

The engine is an XL, 25" and it's mounted with 1 hole up, 1 hole down. I don't want to move it just yet as I am still working through other issues that may be keeping me from reaching max RPM.

I'm on a trail of unraveling all the problems this motor came with. I go into Guardian mode a few times every trip, but the reason has not been clear. Most recently and just one time out all Guardian mode occurrences, I got a "Block Coolant Pressure" fault on VesselView mobile. Investigating the pressure sensor and replacing the water pump is next on my todo list.

So far, I've replaced or verified:
1. Alternator (new)
2. Batteries (Optima Bluetop) and battery cables (1/0 AWG)
3. TPS (verified 0.5-4.7V)
4. Keyswitch wiring harness (new, old one had an intermittent open circuit on ign wire)
5. Oil tank float switch (verified by unplugging and measuring)

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I concur, the prop conversation should be paused till the engine issues are resolved.

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That should be easy to check.
Move the console throttle lever to full and see if the throttle arm is FULL ON under the engine cover.

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Glad to hear this is an easy check. I'm not yet fully familiar with what "FULL ON" should look like, but I'll refer to the service manual and maybe some of my own intuition.

I'll be sure to report back on my progress, which may take a few weeks. Thanks all for your advice and support.

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I managed to get to the boat yard to take a look with DIACOM diagnostic software.

1. Shift switch seems to work fine, but it could be intermittent. Part still hasn't arrived yet.

2. With the throttle control fully forward, there's still ~1/8" of play going toward WOT on the throttle body lever. It seems I need to adjust this.

3. I have zero block pressure at idle and 1100 RPM. I didn't feel comfortable running higher since I'm on land running on ear muffs. There is water coming out of the pressure sensor hose when I disconnect it. The cable connection looks secure. I have a replacement sensor on order.

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Screenshot @ 1100 RPM

Shift switch seems operational. There's zero block pressure. There's a 42% power limit? Maybe this is caused by the zero block pressure?

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Fault codes here don't seem applicable

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I got a new block pressure sensor and new water pump installed. Now I get 0.8-1.2 PSI reading at idle on ear muffs. Next week, I’ll try to get it on the water for a real test.

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I finally got a sea trial in with a new block pressure sensor and water pump. Got up to 10 psi at 3100 rpm. Too rough to go any faster, but it runs well now without going into guardian mode. Thanks for everyone’s help.