150hp Optimax - Low RPM - Fuel or Spark?

[olemon]

I have a couple of problems with this motor Ser: 0T148359. Service Manual should arrive this week. I posted about an intermittent overheat alarm last Friday, off to get some parts today for that and this....

Also have worsening intermittent problem where cannot get over 3xxxrpm coming out of hole. Hit the throttle, nope, idle...try again, nope, idle, try again. Last time out, after I got on plane at reduced rpm, I stayed near the landing and after few minutes all cylinders were firing and had full power, 5400rpm WOT. Later, it dropped back to 4600 or so again, picked up.

I've had two shops look at it before, both for the overheat alarm and this. One shop replaced a plug. Anyway, I pulled the plugs and inspected wires. Two plugs were pretty dirty, especially #6, plug wires on #3 and #6 have rusted connectors on the plug ends, again, especially #6. I attached photo of plugs. I'm replacing wires and plugs.

On this engine, could #6 account for all of the reduced rpm, or would it take more than one cylinder dropping out to get that much reduction?

BTW I have tested all coils with multi-meter per diagnostics guide. They check out ok. The injectors check out too, but I'm thinking spark is the problem and not fuel, but I sure appreciate any help/comments. Thanks.

[olemon]

Got manual today and picked up a spark tester. I'll be ordering parts on-line though, local dealer only has 1 plug wire and 1 thermostat.

[olemon]

Spark test was good. Runs just fine at idle and up to 1000 rpm. Guess I'll start researching the fuel path. Do compressors fail very often? What about high pressure fuel pumps?

[EuropeanAM]

Rather than guessing... I would recommend that you continue to check ALL of the basics (or have them checked):

-Compression Test
-Spark Test (this will INCLUDE new spark plugs... you need them)
-FUEL QUALITY, DELIVERY, and AIR/FUEL PRESSURE TESTS + LEAKDOWN OF BOTH PRESSURES

As evidenced by your spark plugs, you have a RICH OPERATING CONDITION (and I highly suspect it's related to a loss of spark, OR excess fuel being delivered due to a problem in the system).

[olemon]

Ok, thanks. Too bad I can't bring it to you. Prolly have to try local shop, for the third time, if I can't find something obvious.

[EuropeanAM]

Those Air/Fuel Pressure tests (and readings taken 5 seconds, 10 seconds, and 15 seconds after engine shutdown) may be very benfitial.

[olemon]

Ok. I found the cause for high temp alarm. Now I can focus on this. While running/testing today, I could not reach more than 4600 rpm WOT, about 3000 out of the hole. Also, I am hearing a rattle, like clinking a light chain maybe, or shaking a jar of coins. Only happens at higher rpm. Sounds like it's coming from front of engine, but I was alone and can't be sure.

Could the reed block at the throttle body make such a noise? Could be anything I guess, but I'm inclined to start snooping. I know I still need new set of plugs, and I'll start there, but the engine is running rich and not at full power. Assuming it's not plugs, to be determined, what should I NOT do in terms of tearing down, inspecting and putting back together? Can I safely check the pressure and fuel regulators on the fuel rails? Can I tear down the air compressor?

Anybody else have similar problem? Thanks in advance.

[EuropeanAM]

This clinking sound you described does not sound good.

I would recommend that you STOP where you're at, and enlist the "hands-on expertise" of a Certified or Master Technician.

I do NOT recommend that you attempt to disassemble your air compressor, OR the fuel rails. Replacement parts are seldom available.

Were the air/fuel pressures checked, or was that step bypassed?

You also might simply remove the belt, and see if the air compressor pulley exibits any signs of lateral or up-and-down movement (or any rattle in the compressor when turned back and forth by hand).

[olemon]

Have not gone past spark test and visual inspection - prolly beyond my ability/tools to do much testing. I see a dealer/technician in my near future. I'll do as you suggest and see if tensioner/alternator/compressor pulleys have any play or slop in them. Thanks.

[olemon]

There is side to side play in the composite or plastic Cam, and the Roller (from parts diagram) spinning on its pin rattles. That's where the noise is coming from. It definitely is a rattle when running and not constant, comes and goes. I didn't describe the sound very well. Here are couple pics. Guess I'll have to bite the bullet and take it in.

[EuropeanAM]

SOME side-to-side movement in the cam is normal. Any noise here is normally not noticable with the cowling ON, however.

I'd recommend getting it in for inspection/testing.

[blackxpress]

As Don said that rattling noise means get it in the shop ASAP. Otherwise, to answer your earlier question one plug can cause the rpm loss you describe.

[pfishing]

Olemon - what was the conclusion of your problem?

[Wildcat Dude]

and you're really close to an EXCELLENT shop I used in Houma LA - take it there those guys are GOOD (well Excellent actually)
Evolution Marine
Address: 1413 Barrow St, Houma, LA 70360
Phone:(985) 851-7689

[SilverFox579]

Olemon - what was the conclusion of your problem?

Since his last reply to this topic 6-5-2012 I checked to see when he last logged on...

Last Activity
06-16-2012 06:26 PM

Based on the above, I highly doubt you'll get a response.

[Wildcat Dude]

Might not have the funds - that would hurt plans for sure.

[olemon]

My apologies for those unanswered posts. I haven't logged on here in a few years, but I still have this boat and it still has the same troubles. Hardly use it and looking to sell, trying to decide if it's worth the bucks to try and fix it. Since I last posted I took it to a local shop. The tech checked everything out, cleared the alarms and experienced the same problems during test runs, but could not find the culprit. He thought he remembered an issue with this model/year about a low voltage tripping the alarm. Ever hear of that?

The last run I made was several months ago. Ran for several miles to get to a location. Along the way there was a quarter mile or more of no wake zone. Dropped to idle or just above, Alarm. Shut down, start, idle, alarm...repeat. Once finally past the no-wake zone I got the alarms again while getting on step. But sometimes, even though the alarm is sounding, there is enough power to get out of the hole. When that happens the alarm will silence after a few seconds and we're off and running until the next time.

I called Evolution Marine about a month ago. I took this boat there once before, when I first started having these issues. Maybe I'll try again.

[EuropeanAM]

Have a "hunch" that your problem may be pretty low in the midsection.

I'd strongly suggest you go directly to this link, and obtain the items it suggests. I'm happy to review them for you (if needed):

WARNING HORN "BEEPED"

[olemon]

They haven't run diagnostics yet, computer was down yesterday, but the tech I talked with suspects that the alarm is an over-heat and could be the base plate, gasket, o-ring, under the impeller which techs rarely change out when installing a new one.

[JOE54]

^^^^ agree it could youd have low block psi for sure