358 with a 300-400 rpm difference between engines
 

The Starboard engine lags the Port engine by 300-400 rpm's. I have ran bravo 1's and lab finished bravo 1's with the same results. Engine has been checked by a dealer for computer code faults and compression check. The engines are new HP 525's with 30 hours on them. Can anyone tell me what type of engine rpm differences they are getting and what differences are acceptable. I thought Mercury was to match twin motors.

Re: 358 with a 300-400 rpm difference between engines
 

power steering

Re: 358 with a 300-400 rpm difference between engines
 

It should have PS pumps on both motors; one just set to recirculate. This is easy to check, just make sure you have same accessories on both motors.

Are you sure your throttles cables are set properly? Take off your air cleaners, with the engines off, and move your throttles together, and then compare the throttle body butterflies' postions, especially at 'full throttle'. You may have to adjust your cables for one that is not openning all the way.

Re: 358 with a 300-400 rpm difference between engines
 

Have you synchronized them by ear? You should be able to open your exhaust when on plane, and listen to the HUMMMMMM between both engines. When they hummm together, now what does the tach's read?

If still 3-400 rpms low on gauge, then you may have a sending/gauge problem.

Re: 358 with a 300-400 rpm difference between engines
 

I have checked the throttle butterflys and they are together. Ialso have checked the engines by sound and the starboard engine is down on rpm's compared to the port. the only way that I have been able to sink themis to move the starboard engine throttle ahead of the port at crusing speed and to trim the starboard much more than the port at wot. Any other info to solve this would be appreciated.

Re: 358 with a 300-400 rpm difference between engines
 

prop pitch. Have your props checked to make sure they are what they say they are.
You might want to have your gears checked to make sure they are the same

Re: 358 with a 300-400 rpm difference between engines
 

Bill-
I believe you've got the answer. I had a pair of 26's that were 200 rpm's off, took them off and put on 28's and problem solved.

Re: 358 with a 300-400 rpm difference between engines
 

I nebber thought of that Adam.

Try switching your props, and running the boat in Reverse (which will now be forward) to see if the problem switches side to side. Be careful though, it will affect handling and docking is a bear with reversed props.

Re: 358 with a 300-400 rpm difference between engines
 

If you have the engines synched by ear properly and still see a difference, I would be checking the tachs. When the resonance goes away, the rpm's are very close.

Re: 358 with a 300-400 rpm difference between engines
 

I have changed the props to Hydromotive P5-X's and the RPM's are within 150. The engines do not have 2 power stering pumps. Only the Starboard engine has a pump and the Port has an idler. The stern drives are ITS. Could this be why there is only one pump. The 31SS that I previously had had a pump on each engine. I would also recommend to anyone that has a 358 to try the Hydromotive 5 blade props. The handling of the boat improves like the difference in day and night and the efficency of the prop goes to 92-93% as compaired to 85% with the Bravo 1 4 blades.

Re: 358 with a 300-400 rpm difference between engines
 

Viper, I have a 2000 358 with 502's and am considering repowering with 525's when I have to do some work on them.What kind of speeds are you getting and what kind of handling changes did you experience with new props.

Re: 358 with a 300-400 rpm difference between engines
 

Diablo, the biggest change in handling with the Hydromotive P5-X is additional stern lift given by these props that results in having to run almost no tab at slower speeds to keep the bow down and to stop porposing. Also, acceleration is dramatically improve out of the hole and any speed that you want to hammer the throttles. The speeds I have run with the boat on flat fresh water are:

79.9 Bravo 1 Stock 30P 5000-5100 RPM
79.1 Hydromotive P-5X 28P 4800-4900 RPM
76.2 Bravo 1 Lab Finished 5100-5200 RPM

I think I can improve the speeds a little more with 27P Hydromotive props as I was only turning 4800-4900 rpm's with the 28's. I have a set of 27's on the way and I plan to try them out this weekend. I think I can exceed the top end 0f the Bravo 1's. What horsepower are your 502's and what current props are you running and what type of speeds are you getting?

Re: 358 with a 300-400 rpm difference between engines
 

Diablo- Did you previously own a 37 OL called "Fra-Diablo"?

Re: 358 with a 300-400 rpm difference between engines
 

Sorry I haven't got back to you guys sooner but I was out of town and just got back to the office.To answer the first question the 358 sonic is the first offshore boat I owned,although I've had plenty of other smaller boats.I keep my boat down in Florida around Bonita Springs although i live the Chicago area.My 502's are 415 hp currently with cmi headers and reprogramed ecu with 26p bravo's and the best i've ever got out of the boat in florida on a cool day was 69.3 at 5050 rpm.Hope to do something different with the engines in the next year after my warranty expires.