*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Random Quote: GOD does not deduct from a man's alotted time, those hours spent fishing.
I have a pair of 135 Optimax's on my 23 Donzi. I have noticed that when running both engines at 3500 rpm and punch the port throttle I get an immediate increase in rpm, engine noise and response. The starboard engine does pick up speed and some engine noise but the kick is just not the same. Both are trimmed the same. Mechanic says all is fine, but I just don't think so. Both enignes will max out rpms. Any ideas I can try?
I have a pair of those same engines on my 24 Grady. One is standard rotation and the other is counter rotating. When I push my throttles to get on plane, they both respond equally. The Tach syncronizer shows a slight difference but both tachs are reading the same RPM's. They run and sound good at 4000 rpm and 30 knots. My only issues with these engines is a hard cold starting situation. I am waiting for a Merc Rep to come and look at my engines. Other than that initial cold start these have been awesome engines and I am very pleased!
Get a mechanic to search the computer for trouble codes using the DDT meter. Some of these Opti's had issues with the throttle position sensors. These engines use two non adjustable TPS sensors. If one qits you engine speed will be limited to 3000 RPM's and if both the inner and outer quit your engine will be reduced to idle speed only. One nice feature of the DDT is that it allows a cylinder balance test. That is it is capable of shorting out one cylinder at a time to isolate problems. as each cylinder is shorted there should be a stumble and drop in rpm's. If there is no change then you have found a problem on that particular cylinder. (Plug, wire, coil, injector, etc...)
Thanks for all the suggestions. The engines are one standard and the other counter rotation, gear cases are the same numerical ratio. I did notice when putting the boat back on the lift that the port trim tab was half way down and would not come up. This would raise the port aft and lower the starboard bow. This could have causes the port engine to cavitate more and speed up more. I just finished fixing the wiring and wouldn't you know that the tide is out and it will be tomorrw before I try it out again. Will let you know how she runs. BTW, no codes from the DDT.
There is two ways to test the TPS, first is a heat test using a hair dryer to see if the ohmeter values change as the TPS heats up, second is the pressure test by squeezing the unit with your fingers. This is assuming that the DDT gets no error codes. Also if the TPS fails the ECM resorts to the butterfly in the intake for readings and reduces the RPM's by approx 10 percent. Also the MAP sensor in the intake is subject to some light oil fouling which can mimic a bad TPS yet give no fault indication.
Your situation sounds as though one motor may cavitate slightly and therefore increase RPM's quicker. Just an idea. I have much experience with Optis, since I got sick of letting the dealer misdiagnose the problems. Since then it has been months of reliable use and happiness.
The boat handles better, but the starboard engine still does not come up to speed as quickly as the port engine. Cavitation theory I had is not the problem. Going over to another mechanic this afternoon to see if they can determine the problem.
