Tohatsu 15hp Efi Gurgling??

Mattallica · 17 March 2020, 17:27

Got some video of my outboard yesterday with the gurgling noise. Is this normal ? I have raised the outboard 20mm so the cavitation plate is now only 10mm below the hull. I was running on the second hole nearest the transom. There is a gurgling noise that is bugging me it sound like its sucking air in?? The water is pumping fine and doesnt ever get interrupted. Is this cavitation or ventilation?? If you listen carefully you can hear it.

https://youtu.be/lNDYS5e79wM

beamishken · 17 March 2020, 22:42

Quote:

Originally Posted by Mattallica

Got some video of my outboard yesterday with the gurgling noise. Is this normal ? I have raised the outboard 20mm so the cavitation plate is now only 10mm below the hull. I was running on the second hole nearest the transom. There is a gurgling noise that is bugging me it sound like its sucking air in?? The water is pumping fine and doesnt ever get interrupted. Is this cavitation or ventilation?? If you listen carefully you can hear it.

https://youtu.be/lNDYS5e79wM

Cant make out any untoward noise but I'd say your still too deep as a minimum engine should be level with the hull & usually slightly above gives the best performance results

mikehhogg · 18 March 2020, 00:44

is it gurgling only when underway.

Mattallica · 18 March 2020, 06:08

Yeah no gurgling when in neutral or throttled down in forward or reverse.

jeffstevens763@g · 18 March 2020, 08:49

are you at WOT

Mattallica · 18 March 2020, 09:26

Quote:

Originally Posted by jeffstevens763@g

are you at WOT

Wide open I dont get any gurgling.

jeffstevens763@g · 18 March 2020, 09:52

Quote:

Originally Posted by Mattallica

Wide open I dont get any gurgling.

i can make out what you mean its normal at low speeds the exhaust gases hitting the wash from the boat and the engine leg once your at a good planning speed you wont notice it

Mattallica · 18 March 2020, 09:53

Quote:

Originally Posted by jeffstevens763@g

i can make out what you mean its normal at low speeds the exhaust gases hitting the wash from the boat and the engine leg once your at a good planning speed you wont notice it

That's good to hear thanks very new to all this and didnt want to be doing any harm to the engine.

jeffstevens763@g · 18 March 2020, 10:02

Quote:

Originally Posted by Mattallica

That's good to hear thanks very new to all this and didnt want to be doing any harm to the engine.

just watched your vid nice little setup i know the area well durdle door in the summer will be a nice trip for you enjoy

Fenlander · 18 March 2020, 11:00

I agree with Jeff... listening/looking at the video it seems about normal. If you move a camera about from different angles over the transom it will pick up noise variations that aren't always heard from your normal seated position. Engine sounds smooth though.

Like Beamishken I wondered if you are still a bit deep with the outboard.

chipko · 18 March 2020, 11:40

We get the exact same gurgling from our Mariner 20efi. Odd and annoying isn’t it. To be honest I’d initially come to the conclusion it was more the fault of the hull, but other Tohatsu/Merc/Mariner (same motors) are also experiencing this on different boats, it may well be a quirk of these motors.

Whilst our T38 is prone to random sporadic ventilation issues, we get this gurgling all the time with no apparent loss of power or speed (22-23 knots one up on a good day). So not too concerned.

With all due respect and, in my opinion, I really don't think this gurgling is generated by exhaust gases.

I also don't think you'll get any noticeable performance gain by raising the motor higher. You've already got the av plate within 10mm of the keel which is usually pretty good on a sib. Yes, the av plate is below water surface whilst planing, but there is no excessive splashing, and on sibs it's usual to run slightly deeper than ideal to limit ventilation in the turns. On ribs we have the luxury of trimming down for grip in the turns. More of a compromise on a sib.

Perhaps worth experimenting if you can trim out a hole or two to eek out a bit more straight line speed. Try trimming out one hole at time until it ventilates, then go back down one hole. This should the give you the optimum setting, at least in a straight line. If then getting excessive ventilation in the turns you might have to trim back in one more hole. It's all a compromise and we tend to accept a bit of ventilation in tight turns to get good straight line performance.

Watched your vids, nice one. Enjoy your new rig.

jeffstevens763@g · 18 March 2020, 12:26

With all due respect and, in my opinion, I really don't think this gurgling is generated by exhaust gases.

ever blown through a straw into a glass of water x that 100 times or more

beamishken · 18 March 2020, 13:08

Quote:

Originally Posted by chipko

We get the exact same gurgling from our Mariner 20efi. Odd and annoying isn’t it. To be honest I’d initially come to the conclusion it was more the fault of the hull, but other Tohatsu/Merc/Mariner (same motors) are also experiencing this on different boats, it may well be a quirk of these motors.

Whilst our T38 is prone to random sporadic ventilation issues, we get this gurgling all the time with no apparent loss of power or speed (22-23 knots one up on a good day). So not too concerned.

With all due respect and, in my opinion, I really don't think this gurgling is generated by exhaust gases.

I also don't think you'll get any noticeable performance gain by raising the motor higher. You've already got the av plate within 10mm of the keel which is usually pretty good on a sib. Yes, the av plate is below water surface whilst planing, but there is no excessive splashing, and on sibs it's usual to run slightly deeper than ideal to limit ventilation in the turns. On ribs we have the luxury of trimming down for grip in the turns. More of a compromise on a sib.

Perhaps worth experimenting if you can trim out a hole or two to eek out a bit more straight line speed. Try trimming out one hole at time until it ventilates, then go back down one hole. This should the give you the optimum setting, at least in a straight line. If then getting excessive ventilation in the turns you might have to trim back in one more hole. It's all a compromise and we tend to accept a bit of ventilation in tight turns to get good straight line performance.

Watched your vids, nice one. Enjoy your new rig.

Prety much the same advice goes for lifting the engine, usually trail and error. However if you can make the gains by lifting the engine then that is preferable to trimming out as it avoids the nose in the air attitude when climbing onto the plane.

chipko · 18 March 2020, 13:46

Hear what you're saying, but again with respect, I have exactly the same motor and getting the exact same gurgling. It is much more pronounced and distinctive than on the video sound when heard first hand. On all the many similar size motors we've run over the years, all with through prop exhausts, non have exhibited anything approaching this sound. The big giveaway, as far as I'm concerned, is this sound is linear with speed through water whereas an exhaust gurgle will vary with engine load/revs.

I'm also a big advocate of raising motor as far as you can for max efficiency.

Locozodiac · 18 March 2020, 16:36

Those Tohatsu motors loves running while the water flow at speed skims right under the upper splash platem as seen in this didactic video...

https://www.youtube.com/watch?v=oBeZ...ature=youtu.be

Raise or lower the motor accordingly on transom till that running position is fully achieved.

Happy Boating

Locozodiac · 19 March 2020, 16:23

If my eyes are not playing tricks on me, that motor sits way up on transom. This is the best lower leg height for Tohatsu motors installations. Motor will achieve best prop grip with high output thrust, soon after can go for for a prop maximization to a lower pitch one from factory delivered and will fly that combo out of UK...

For visual clarification post another motor video shot sideways while running at full throttle. The boat must be running on flat calm water cond if possible, with deck load well distributed and motor trimmed to 90 deg as in pics.

Sorry mates but max motor efficiency and water performance will only be dialed at that precise lower leg height which it's stated nowhere, was dialed under intensive water trials while playing with different lower leg heights.....

Happy Boating

Mattallica · 19 March 2020, 16:27

Thanks for your advice I'll try and get some more pics and vids next time I'm out. I currently have it raised so that the cavitation plate is 10mm below the hull.

jeffstevens763@g · 19 March 2020, 16:43

Quote:

Originally Posted by Mattallica

Thanks for your advice I'll try and get some more pics and vids next time I'm out. I currently have it raised so that the cavitation plate is 10mm below the hull.

my new excel is the same ive got mine raised 40mm and is still 10mm low but that doesn't bother me it'll be hardly noticeable IMO, the transom angle seems to be very steep on the excel more so than my old mercury.

Mattallica · 19 March 2020, 16:46

Quote:

Originally Posted by jeffstevens763@g

my new excel is the same ive got mine raised 40mm and is still 10mm low but that doesn't bother me it'll be hardly noticeable IMO, the transom angle seems to be very steep on the excel more so than my old mercury.

How did you manage to raise it that high without the outboard clamps being off the transom plate ? I think I might be able to squeeze another 5 or 10mm more max.

jeffstevens763@g · 19 March 2020, 18:16

Have a look at my thread excel 435 fit out the clamps are just on the plate