Water spraying over engine and aft on Marlin Rib

Cool Hand Luke · 19 August 2008, 22:53

I hope somebody can help.

I have a 6.1m Marlin Rib with a Mercury 150hp 2 stroke outboard. I have had the boat about three years and I think the boat was built in 2001. The engine is definately a 2001 model. I had the engine serviced recently and since then the engine seems to force a large amount of seawater over the aft of the boat as soon as the boat gets on the plane. Its not coming from the cooling water outlet but seems to be being forced up by the prop. I have tried adjusting the trim but its makes no differerence. Its a bit alarming to see the water being forced over part of the engine and against the rear of the boat. The boat still goes well and does 35 knots reasonably easily. The prop was not changed and I cannot see that the service changed anything substantial on the boat.

Anyone any ideas?

Limey Linda · 19 August 2008, 22:58

Quote:

Originally Posted by Cool Hand Luke

I hope somebody can help.

I have a 6.1m Marlin Rib with a Mercury 150hp 2 stroke outboard. I have had the boat about three years and I think the boat was built in 2001. The engine is definately a 2001 model. I had the engine serviced recently and since then the engine seems to force a large amount of seawater over the aft of the boat as soon as the boat gets on the plane. Its not coming from the cooling water outlet but seems to be being forced up by the prop. I have tried adjusting the trim but its makes no differerence. Its a bit alarming to see the water being forced over part of the engine and against the rear of the boat. The boat still goes well and does 35 knots reasonably easily. The prop was not changed and I cannot see that the service changed anything substantial on the boat.

Anyone any ideas?

Maybe, the engine is tilted in (down) way to far. Maybe, the service person failed to refit the tilt lock cross pin.

Cool Hand Luke · 19 August 2008, 23:29

Excuse my ignorance but which bit is that?

Nos4r2 · 19 August 2008, 23:46

the pin that limits how far down the engine can trim.

Cool Hand Luke · 20 August 2008, 00:05

The problem still sppears when I trim the engine quite high. Where does the pin fit in the outboard?

Locozodiac · 20 August 2008, 00:44

Quote:

Originally Posted by Cool Hand Luke

I hope somebody can help.

I have a 6.1m Marlin Rib with a Mercury 150hp 2 stroke outboard. I have had the boat about three years and I think the boat was built in 2001. The engine is definately a 2001 model. I had the engine serviced recently and since then the engine seems to force a large amount of seawater over the aft of the boat as soon as the boat gets on the plane. Its not coming from the cooling water outlet but seems to be being forced up by the prop. I have tried adjusting the trim but its makes no differerence. Its a bit alarming to see the water being forced over part of the engine and against the rear of the boat. The boat still goes well and does 35 knots reasonably easily. The prop was not changed and I cannot see that the service changed anything substantial on the boat.

Anyone any ideas?

Each engine manufacturer recommends a max and min height between boat's bottom to the anticavitation plate, if too low will spray water upwards and sometimes into the boat. Look for the recommenden 150 HP mim/max engine height and see it's inside the manufacturer's recommended height. Ribs behaves different to sibs in this splash issue, so a tech inquire to the boat's manufacturer will be advisable, ask the height parameters with respect to the ribs deep v keel bottom to the anticav plate in case other adjustments are found ok.

Happy Ribbing

Limey Linda · 20 August 2008, 04:16

Loco makes a good point . If you have your engine set too low this could happen. HOWEVER, THE PROBLEM WAS NOT THERE BEORE THE SERVICE.
Check the tilt cross pin first.

PS. you obviously do not have or have read the service or factory manual. Do it, it will save you a bunch of money and you will not have to ask "which bit is that"

JABS · 20 August 2008, 07:31

Is there a feed to a 'water pressure' speedo hose that has come off??

Bigmuz7 · 20 August 2008, 07:42

Sounds like an external sonar unit, such as for depth or a dish finder has been knocked out of position by something/someone and giving you an unusual spray pattern when under way .. anything like that screwed on to the transom on the outside ?

*edit*
I have one that does exactly this at the best of times, and I had to make a deflector to cure the problem, as water got trapped in the mounting when under way and threw a jet up the starboard side of the engine soaking it constantly

Cool Hand Luke · 20 August 2008, 08:58

I did think the boat had the appearance of sitting very low in the water so I'll need to find a manual to check out this pin that should be there. I do see in the auxilliary engine a pin that goes across that stops the engine going down too far that does not seem to be in the main engine and maybe the engine is lowering too much in the water by way of tilt and then triming too low.

Interestingly one of the things that the service guy did was refit the speed paddle wheel (which had come loose and not been attached for a long time) onto the bottom of the transom. I thought that this might be part of the problem so I took the boat out on Sunday and took the paddle wheel off. I have yet to try the boat again.

Maybe its a combination of both of the problems....

Anyone know where I would find a manual online?

yorfuoj · 27 August 2008, 11:22

The pin has nothing to do with your problem, as you said that it occurs even with high trim.

Your engine was probably removed from the transom by the repair man, end re-fitted in another vertical position, too low.

This kind of problem is very frequent, as all the engine installation manual insist to install the motor with the anti-cavitation (ventilation) plate set 2cm below the hull bottom.

This is good to get a very efficient trim action, but very bad for speed and water spray because the water bangs into the leg above the plate and is sprayed vertically - and possibly enters into the motor hood.

Solution : ask to have your engine raised in order to get this plate 2 to 3cm above the hull bottom line

Cool Hand Luke · 02 September 2008, 15:17

Thanks everyone for all the suggestions.

I have taken off the paddle wheel and am going to launch on thurs to see if thats cured the problem. If it hasn't I will take it out and lower the engine on its bracket.

The engineer is admamant he didn't lower the engine but we will see!

I will keep you posted and again thanks for the help.....

Cool Hand Luke · 08 September 2008, 23:46

We removed the speedo log paddle wheel from just under the transom on the boat and hey presto the problem has gone away. This had been loose previously and this is obviously why. We have a plotter for speed anyway.

No water spray and boat going great. 37 knots at one point with boat full of fuel with five adults on board.

Thanks for everyones help...

Off to Skye for the weekend!