Mercury 115 CT 2.1l trim relief valve

[QBhoy]

Hi all

i might have asked this before, but this fairly new to me engine is an amazing thing, being one of the new mercs...but only thing bothering me with it is that it doesn’t quite trim up as high as I’d like a full throttle. It will go to a fair level of trim, then open the relief valve (I think) and nudge down to its threshold.
it will trim up further with no load and as mentioned it will trim up to a fairly high level under load...but most other engines I’ve had outboard or inboard will lift up as far as I like and further under load without issue.
do these newer motors have a relief valve that’s set deliberately sensible ?
boat has been out the water all winter now and I’ve had a look at the manual release vent screw. I got a few mm of a turn tightened on it but pretty sure that’s not enough to be the issue.
anyone have similar findings ? Maybe it’s just how they are these days.

 

[racerone]

Transom wedges are needed perhaps.-----See your trusted workshop / dealer.

 

[QBhoy]

Transom wedges are needed perhaps.-----See your trusted workshop / dealer.

Not sure that’s the issue racerone. It sits well enough and will trim enough for most folk but just never know any other I’ve had to actually lift a relief valve if too much trim. Any other will lift clear if the water and air out the prop. This won’t allow that.

 

[racerone]

Replace power trim / tilt or take it apart and see what is wrong.-----A relief valve kit may be available.----Your serial # is ?

 

[QBhoy]

Replace power trim / tilt or take it apart and see what is wrong.-----A relief valve kit may be available.----Your serial # is ?

Not sure if the serial number at this very moment. I’ll check.
the engine is almost brand new, all be it from 2016. It sat for a couple of years unused after run in. Then I got it last year.
so you think it’s not probably normal perhaps for it to do this ? Not that I really need to trim much more. But I naturally think it should go a little further and as mentioned never known any other of my engines to give in under load. I know that there has been some sort of limit put on it at the very upper limit of the tilt for fill up trailer mode. To stop it hitting the boat. I know this because it won’t tilt far enough to allow the manual tilt trailer lock bar to get into position.

 

[QBhoy]

Replace power trim / tilt or take it apart and see what is wrong.-----A relief valve kit may be available.----Your serial # is ?

Serial number is
2b219032

 

[racerone]

The pressure in the hydraulic system would be the same 20% trimmed up or 80% trimmed up??

 

[QBhoy]

The pressure in the hydraulic system would be the same 20% trimmed up or 80% trimmed up??

You think so ? At full rpm and also trying to lift the hull you’d imagine there would be more load on the hydraulic system than there would be any other time ?

 

[Faztbullet]

It will go to a fair level of trim, then open the relief valve (I think) and nudge down to its threshold. ​

it will trim up further with no load and as mentioned it will trim up to a fairly high level under load.do these newer motors have a relief valve that’s set deliberately sensible ? ​

That's the way a single ram trim unit operates

 

[QBhoy]

Thanks Faztbullet. Suppose that’s exactly what I’m wondering. If it’s normal. Any other outboard boats I’ve had have been faster and lighter things. They will lift as far as I like usually, from memory.

 

[Faztbullet]

Merc/OMC 3 ram units only lift as far as the short trim rods and then when under light load the tilt ram will work.

 

[Texasmark]

Recalling, Merc. advertised in their sales brochures tilt-trim limits of -4* to +20*. Of that, trim pressures (caused by increasing engine thrust) activated the over pressure pop-off when the boat speed reached a certain level with the engine attitude exceeding something like +7 of that +20....the +20 number was to get lower units out of the water when boats were moored/stored in the water at marinas.

I can compare 2 boats of mine with 90 and 115 engines and different transom angles and the differences due to the one with the increased trim angle availability due to a near vertical transom, was that I could make one blow out at WOT with the trim button, and the other one couldn't.....was no fault of the engine, just built up enough pressure to activate the over pressure bypass where the transom tilt angle was too great.

I've been playing around whereby I would deliberately trim out at an angle exceeding the trim-tilt conversion point, hammer down on the throttle and cause the engine to tuck in from a tilt position, down to the upper limit of the trim range.......never mind where the bow of the boat was when I was doing that. Grin.

I agree with Racerone, you need to install wedges on the bottom of the trim bracket to take out some of the transom angle. Not much time involved, you could make them out of wood for the test, only need a few degrees, a couple of longer bolts for the bottom of the transom bracket.....maybe half a day to make and install the parts and run out for the test. Then......if you haven't found your solution worry about tearing into things and fixing something that ain't necessarily "broke".

 

[QBhoy]

Recalling, Merc. advertised in their sales brochures tilt-trim limits of -4* to +20*. Of that, trim pressures (caused by increasing engine thrust) activated the over pressure pop-off when the boat speed reached a certain level with the engine attitude exceeding something like +7 of that +20....the +20 number was to get lower units out of the water when boats were moored/stored in the water at marinas.

I can compare 2 boats of mine with 90 and 115 engines and different transom angles and the differences due to the one with the increased trim angle availability due to a near vertical transom, was that I could make one blow out at WOT with the trim button, and the other one couldn't.....was no fault of the engine, just built up enough pressure to activate the over pressure bypass where the transom tilt angle was too great.

I've been playing around whereby I would deliberately trim out at an angle exceeding the trim-tilt conversion point, hammer down on the throttle and cause the engine to tuck in from a tilt position, down to the upper limit of the trim range.......never mind where the bow of the boat was when I was doing that. Grin.

I agree with Racerone, you need to install wedges on the bottom of the trim bracket to take out some of the transom angle. Not much time involved, you could make them out of wood for the test, only need a few degrees, a couple of longer bolts for the bottom of the transom bracket.....maybe half a day to make and install the parts and run out for the test. Then......if you haven't found your solution worry about tearing into things and fixing something that ain't necessarily "broke".

Ok. Thanks to both of you for the info. You may well both be right.
I’m actually at the boat just now. The engine height is very conservative on the transom. It’s set up in the top hole (as low as engine height it will go). I remember thinking the cav plate was about level with the line of the hull (a little low perhaps) but literally as soon as I bought the boat, it went in the water. Been put all winter and time to sort out niggles like this. Certainly the transom has an inward angle and you both may be spot on with needing wedges.
Perhaps lifting the engine might reduce the issue too.

thanks again guys.

 

[QBhoy]

Think you’re right guys. Very inward angled transom. A wedge would help for sure.