Engine trim synchronisation problems.

[madoth]

Hello everyone,

we are operating a new 6.4m RIB lifeboat which is powered by two Suzuki DF90A engines. The engine trim (tilt) mechanism can be switched to 'dual trim', so either trim button on the throttles tilts both engines. Unfortunately the two trim motors are powered by two separate battery buses, hence there is no synchronization. (different voltage drops across motors leads to different trim speeds) At the moment the trim needs constant manual adjusting, which is a pain in the backside if operating over a wide speed range, which we often do.
Seeing that most larger lifeboats and RIBs are powered by two engines, I was just wondering if anyone has found a solution to this. (e.g. voltage bridge...)

Suzuki told us this behaviour was normal, which I don't agree with on a boat that cost as the best part of 100k £.

Many thanks,

Matt

 

[rafiki_]

Matt, a warm welcome to the forum. I am sorry that I can't help with your problem, but I thought I'd bump it back up to the top in case so that others will see it.

 

[Red]

Your first problem is that you have chosen Suzuki to power your rescue craft. Secondly although Suzuki produce engine controls - for a rescue craft the controls need to be much higher spec than the normal Suzuki outboard controls. I would recommend replacing the Suzuki controls with another product. Top of the range or your budget would be Kobelt and you may find that Suzuki offer a higher/commercial rated product but give Hypromarine in Lymington a call as they only recommend good stuff...

 

[MapisM]

the two trim motors are powered by two separate battery buses, hence there is no synchronization. (different voltage drops across motors leads to different trim speeds)

Hi and welcome to the madhouse.
I have more experience with outdrives, rather than outboards.
But also with outdrive powered boats requiring frequent trim adjustments (also of flaps btw), the typical setup is with 3 switches: 1 for each engine, plus a third one which moves both at the same time (simply by mean of a twin contacts switch, hence with no "real" synchronization, but more than good enough).
It sounds weird that the voltage difference can be so relevant to affect significantly the trim speed, I would check that first.

 

[madoth]

rafiki:
Many thanks!
Red:
I see your point, will look into it! Thanks
MapisM:
The voltage issue is an educated guess. Both trim motors are brand new, so I doubt that there are any internal differences significant enough to cause this problem, The battery buses supply different parts of the navigation & radio equipment, hence they see different loads. It's exactly what you say, a twin contact switch....