How High can I raise my engine

[capt911]

Hello All,

I have a 1972 MX 16 with an 80's 135HP Merc 2.0 Black Max on the back.

It was running to low in the water and have raised it 2 1/2 inches so far and have about another 1/2 inch or one more hole I can raise it without having to drill now ones or buy a jack plate.

Running a straight edge off the bottom of the Vee the water line is around the 3rd water intake hole down. I have epoxied the top 3 holes so far and installed a water pressure gauge. I was wondering if someone knows how high can I run the engine and how many holes have to stay open to get enough water pressure to cool the engine?

I have about 10-12 psi now at full throttle and asking if anyone can advise me from experience how much higher I can go without having a low water intake on my lower unit?

I have a 23P laser II on it now and are having zero blow out issues and low RPM's as well so know I have lots of room to raise it some more.

Thanks all

[W2F a V-King]

Great boat
I had one of those myself years ago with an old 7 pedal 225. Think my MX was a 1974. Not sure, it was 20+ years ago.

Time for a low water pickup and a nose cone for you. Your asking all the right questions.. Your likely at your limit now, or close to it as far as stock LU and plugging holes in the water inlet holes...I wouldn't want any less pressure at WOT...jmo

Surface the prop, and get a jack plate = Have more fun !!

Later down the road find a 200 power head with the exhaust plate and tuner, and do a swap. Although, the 2.0 Liter mercs can be made to really fly.

Dang...now I am missing my ol boat.

But to answer your question...I ran my 225 with the prop shaft maybe an inch below the surface, 26 or 28 inline merc chopper if memory serves me.

James

[phillnjack]

Before you do anything about low water pick ups and nose cones, set up a camera at the back, take the boat out and see where t
he cav plate is compared to the water. your probably not hardly above it yet.
I did this to my boat and found I was nowhere near as high as I thought I was.
I made a jack plate with 4.5 inch setback and took the engine up 5 1/2 inches higher than the normal highest setting.
I still got tons of water and did not need any low water pick up or blocking off the holes.

look how high I can run my engine compared to the bottom of the hull and still get the same water pressure even in a tight turn..
the bottom pic is the highest and that gave same water pressure as when it was buried deep down.

I ran a pipe from the tell tale up to the steering so I could keep an eye on it and also kept close eye on the temp gauge.
I was shocked at how high the water climbs up the gearcase, I too thought it would definitely run dry.
obviously different boats and motors will be different, but a little video showing what goes on when on the plane and full throttle is well worth knowing.
a water pressure gauge is a brilliant idea, ( next on my list)
I use a cheap water proof borescope linked to my phone, just a cheap $20 one off ebay, gives a decent enough video, 720 image.
I dont have a go pro so I used that.







.

[W2F a V-King]

That's pretty amazing!
The nose on that OMC lower unit must divert a lot of water up to your inlet holes.

Nice!
Agreed... Water pressure gauge is needed!

James

[Jimboat]

I was wondering if someone knows how high can I run the engine and how many holes have to stay open to get enough water pressure to cool the engine?

capt911 - there's only one safe way to know how high you can raise the engine. Install a water pressure gage and watch closely as you're raising the engine. If you don't have a low water pickup now, watching your water pressure will tell you if you need one.

[capt911]

Before you do anything about low water pick ups and nose cones, set up a camera at the back, take the boat out and see where t
he cav plate is compared to the water. your probably not hardly above it yet.
I did this to my boat and found I was nowhere near as high as I thought I was.
I made a jack plate with 4.5 inch setback and took the engine up 5 1/2 inches higher than the normal highest setting.
I still got tons of water and did not need any low water pick up or blocking off the holes.

look how high I can run my engine compared to the bottom of the hull and still get the same water pressure even in a tight turn..
the bottom pic is the highest and that gave same water pressure as when it was buried deep down.

I ran a pipe from the tell tale up to the steering so I could keep an eye on it and also kept close eye on the temp gauge.
I was shocked at how high the water climbs up the gearcase, I too thought it would definitely run dry.
obviously different boats and motors will be different, but a little video showing what goes on when on the plane and full throttle is well worth knowing.
a water pressure gauge is a brilliant idea, ( next on my list)
I use a cheap water proof borescope linked to my phone, just a cheap $20 one off ebay, gives a decent enough video, 720 image.
I dont have a go pro so I used that.







.

Wow great to know will get my Go Pro and give me an excuse to play with it so far only had on handlebars of my bike I see a great new use for it, Thanks. I have never had a temperature gauge, what kind do you use? I will do research as I put a new tach, speedo, and water pressure gauge in but see where knowing temperature would be invaluable

Thanks

[capt911]

capt911 - there's only one safe way to know how high you can raise the engine. Install a water pressure gage and watch closely as you're raising the engine. If you don't have a low water pickup now, watching your water pressure will tell you if you need one.

I installed a water pressure gauge already now looking into a temperature gauge as well. What sort of water pressure is normal in an old 2.0 135 Black Max anyone know? It bounces around but 10-12 PSI seems to be the norm when I am WOT it drops down around 8 when cruising I believe?

Thanks

[olboatman]

I installed a water pressure gauge already now looking into a temperature gauge as well. What sort of water pressure is normal in an old 2.0 135 Black Max anyone know? It bounces around but 10-12 PSI seems to be the norm when I am WOT it drops down around 8 when cruising I believe?

Thanks

You did not mention if these #s are with a new pump impeller. I have found that older pumps (over 2 yrs) showed crazy pressure readings on my 2.4 I had on my Grady. My normal pressure(new pump) was right at 15 lbs @5500 K. Gary

[Jimboat]

I installed a water pressure gauge already now looking into a temperature gauge as well. What sort of water pressure is normal in an old 2.0 135 Black Max anyone know? It bounces around but 10-12 PSI seems to be the norm when I am WOT it drops down around 8 when cruising I believe?

Sounds good! Best of all worlds is to have the temp gage with pressure gage. if you know you're pump is good, then your 10-12 lbs is probably fine. Key is to watch the pressure as you raise engine. if it starts to drop, then you're starting to lose cooling water.

[capt911]

Sounds good! Best of all worlds is to have the temp gage with pressure gage. if you know you're pump is good, then your 10-12 lbs is probably fine. Key is to watch the pressure as you raise engine. if it starts to drop, then you're starting to lose cooling water.

Can you or anyone recommend the best reliable temperature gauge for the money as I have never had one?

[Jimboat]

Can you or anyone recommend the best reliable temperature gauge for the money as I have never had one?

Most marine parts order shops have 'engine head temp gauge w/sender'. such as the Faria gauge here. (I used to buy from Bob's Machine, but don't see it now on their web site). Be sure that you get the sender (thermocouple) too.

[JohnR]

I ran this one for several seasons without issues.

http://www.wholesalemarine.com/amega...by-sierra.html

[W2F a V-King]

Here is one that comes with sender made for an outboard.

http://www.ebay.com/itm/OUTBOARD-CYL...5UItfh&vxp=mtr

James

[phillnjack]

I still dont have a pressure gauge but its on my list ha ha .
I think its another safety idea.
I would realy like to rig one up that would shut the engine down if pressure was to drop to a pre0determined amount.
My problem is I dont know what the actual pressure is supposed to be on my engine ??

what I done for a temporary measure was got some thick walled clear plastic fuel pipe and ran it up to where I steer from and taped it to the rail so I could
watch the water and see it fade off when on plane...
it didn't change at all when I raised the motor right up from normal, I was shocked at this.
I was sure it would be a total failure running the engine this high, others did tell me it would be ok, but I thought no chance and was expecting a dribble at
the very best and a hot engine. just shows how high the water rises from the bullet.

you can get hundreds of different temp gauges and senders.
I use a car one and screwed it straight into a drilled and tapped hole already on the engine cylinder head all the 56 omc heads have this ready for a gauge.

just make sure you get a nice clean part of the top of the cylinder head to take the sender reading from.
its dead easy to fit temp gauge, most use a z bend type thing on the v4, but with some senders you can get a large spacer that is threaded to take the sender.
you then simply either have it welded on the top of head ( way over kill ) or just use something like jb weld to stick it on.
Now once this is on, put some high temp grease on the sender threads and screw it in and for get about it.
at the gauge end it just needs a positive wire to one terminal and the other wire goes back to the sender as this will be the negative.
its exactly how car temp gauges work and is very good.
if you can, the best get a marine gauge as the outboards run cooler than cars, and the needle looks better when pointing dead up in the middle rather than at 11 o'clock on
the cheapo car gauge that I use.
also the marine clocks dont mist up like the auto ones do.

you DO NOT have to have a matched senderand clock. but sometimes its cheaper to buy them together.
you could get a gauge and sender for $20 easy. marine ones are obviously more expensive because the clocks are sealed better.


here is my gauge and ive found it perfect, real cheapo thing, but nothing local was available at the time and I saw this in acar shop on way home from boat shop.
since fitting it ive checked it with temp putty and other temp gauge and with temp meter.
on mine the middle of the clock is 80 degree c, the engine runs at around 60 to 63 so the needle sits at 11 o'clock ish
I am going to swap it out for a merc one I found in a box in my garage, never been fitted as I got this back in the 90's ha ha

[Ramonepb]

I have a 1978 Johnson 115, how do you put a water pressure gauge on this old motor?
I don't see a port.