Under Pressure!

[SANTAFE]

I took my newly rigged boat to the lake Saturday for the second time. The first time I went everything worked as it should. The only change I made between lake trips was to install some tight heads. The second trip the boat would not trim under power. That is with a trim timer and 24 volt trim. If you run the timer when the boat is not under load, it works perfectly. 12 inch drag mid, short ram, with Mercruiser trim pump. I should have tried to trim it on the steering wheel under load, but I didn't. 12 volt on wheel, and 24 volt on trim timer. I know it could be any number of things, but I am not sure where to start. Anybody ever dealt with this before? Any suggestions would be highly appreciated.

BTW you can not hear the trim running with the boat running under heavy load.

[1BadAction]

Out of curiosity, how fast is the trim unloaded? I have the same setup diverter valve split along with an up/down in the mid and haven't bought hoses yet (10 of them, with bulkhead fittings!) I'm dying to see how it all works.

[SANTAFE]

It's about twice as fast off the computer as it is on the wheel. I guess that stands to reason.
I have not really dialed in the digital delay yet, but have it set at 3 tenths of a second delay and 1 second trim.
If I can get it where it will trim under load I may have to do some tweaking.

[flabum1017]

Dumb question.... but do you have the up circuit from the pump going to the bottom of the cylinder? The up cicuit on those pumps have more pressure than the down circuit. The mercruiser pumps have a pressure relief for if you hit something and if you got the hoses backwards (down circuit on the bottom of the cylinder), it won't trim under load.

[SANTAFE]

I will check today. Good tip Thanks.

[90 5.0]

Dumb question.... but do you have the up circuit from the pump going to the bottom of the cylinder? The up cicuit on those pumps have more pressure than the down circuit. The mercruiser pumps have a pressure relief for if you hit something and if you got the hoses backwards (down circuit on the bottom of the cylinder), it won't trim under load.

mine were installed backwards and i always thought the trim was just slow since it was my first 15” mid.

I ran it that way for years on 12v, Installed a trim computer and 24v and the pump blew up about a month later.

This is when I realized they were backwards installing the new pump.

[bigbluechevy454]

Do you have a Tarver or gieger tech clamp?

[WillySteve]

You can pop the reservoir to make sure, the UP side has a thermal relief valve next to it that the DOWN side doesn't have!
I've seen Mercruiser pumps that the outboard fittings would fit fine...."IF you reversed the lines"

[racervboat]

On my 15ft pacecraft it would trim fine but when you hit the throttle motor would fall down all the way the lines were backwards switched them around problem solved?