tohatsu m30a3 not making power

[bspyres]

Tohatsu M30A3 346B s/n 78452 Hi all i have recently bought a M30a3 two stroke on one of those little 8ft addictor boats. it has not been ran in 12 years. the engine is very clean. i put a little marvel oil in the cylinders. new plugs, cleaned the carb (which was suprisingly absolutely spotless) .new 92 gas a little rich about 40-1. the engine runs good on the hose i took it out to the lake and it just doesnt seem to have any power. i am told 30 horse should be a kick in the pants and will pull a skier but this thing barely gets on plane w one person. it eventually gets up to an ok speed but is very dissapointing overall. i did a compression check cold and got 130psi on upper cyl and 132 on lower. i did a leak down check and at 60psi each cylinder only leaked about 1 - 2 psi. re checked the carb. replaced the plugs again top plug is lighter than lower plug. the reeds buzz a little when turning over by hand w carb off like they are doing their job, timing marks seem to line up 2atdc closed 25 btdc open. the prop has a little nick i cant imagine it being that picky but im thinking about taking it to the prop shop.. nobody around here will work on tohatsu's so im on my own unless i wann drag it a couple hours down the freeway. any ideas would be greatly appreciated.. the boat is about 200lbs and im 250.

 

[pvanv]

what is your WOT RPM? You may be pitched wrong...

 

[Sea Rider]

Being an oldie, you could have a spun prop, Rubber on hub could be on its way to become kaput, Prop slips, loses top prop thrust at wot. Make a prop test to check.

Happy Boating

 

[bspyres]

sorry for delayed response guys. I cracked the unavailable plastic carb inlet fitting when i cleaned the carb. i made a new one but that 1/2 thousandth i was off on my cut for the press fit part was a bit too much. Not exactly sure what a proptest consists of but i tried to turn the prop by hand while holding the flywheel. the rubber dampening actually feels very good, flexes but does not slip. i am trying to figure out a tach setup for the WOT RPM check maybe get it out on the lake tomorrow morning (saturday).

 

[Sea Rider]

Prop test is only good when engine its at load and wot, that's on water. Remove prop, turn it over, mark 2 points or a straight line border to border as in pic. Put prop back, go for a wot spin lightly loade, take advantage to check achieved max rpm, remove prop again, and check marks.



If they have moved from where originally drawn, yo have a spun prop in which case need to buy a new prop.

Happy Boating

 

[bspyres]

Ok brand new batch of US 89 fuel 50:1, spotless carb, Gapped both plugs to .039" (new plugs were .020" before) Marked prop to cotter pin. could not find an inductive tach anywhere. so i hooked an old OMC tach i had across the Charging stator. (the reading seemed the same if 2 or 4 was selected on the tach it idles about 1000 and i got 5400 WOT w just me and only about 28mph per the gps (30 downstream 25 upstream) but i got lazy and took it out to the river now i need a new prop for sure =) found a few rocks out there thanks to this drought were having. The prop index mark did not move at all so no slipping. the WOT rpm seems about right unless the tach just wasnt reading right. i can rev it up on the hose and get 5500 without over doing it but it seems about right for revs. i wonder if my expectations are just too high for this little boat. i had hoped i would atleast be able to take a friend in it. of course were both pretty big, but 30HP??? i can order an inductive tach and i guess try again.. anyone suggest a decent one for my toolbox (not a stick on)..

Thanks
Barry

 

[pvanv]

What is your jack height? If you are too low in the water, the boat will be sluggish and will require trimming down to keep the bow from rising. Is the antiventilation plate even with the bottom of the boat? If it is too low, raise it up until it's there, go for a test run, and check the water flow past the motor. The surface of the water should go between the antiventilation plate and the splash plate.

 

[Sea Rider]

Go for a Hardline Hour/Tach meter, easy & friendly to install. you can remove it after testing. Perform same wot test on a straight water course and check max rpm, if with no back or over transom water splashes you're ok. That engine rews up to 5500, if you still achieve low readings with new tach, could optimize combo going for a lower pitch prop to bring revs up a bit towards max side. Usually 150-200 revs +,- for every 1 pitch difference.

Happy Boating

 

[bspyres]

OK got the poor mangled prop taken care of, got a hardline tach installed and Finally made it out to the lake, it wasnt glass smooth water by any means neutral idle was about 1075 and in gear 890 rpm. WOT was about 4700 as high as i saw and still got 27mph on GPS. i talked to the original owner he is about 80lbs smaller than me and he said it did about 50. the boat has the original prop, motor, and setup. i cant drive and look at jack height but paint is wearing just below anticavitation plate. i do see two splashes of water up and back at a 45 degree angle on both sides of the motor up to about a foot and a half above the transom. and there is some spray off both sides of boat going forward and out at a 45. how do i know if i am not getting 5800 WOT rpm because im over propped, or the engine is under performing??

maybe i can see if original owner can take it out for a comparison run.
Thanks for helping on this
Barry

 

[Sea Rider]

Barry, some issues ;

-Prop test was ok, no spun hub, right?
-Are you runninmg a 8 footer with a 30 HP ?

If wot test was done with you alone and achived just 4700 you're lugging the engine. That engine revs 4800-5500. Does carb's butterfly fully opens when at full grip ? If you are experiencing excesive transom over or back splashes, no wonder engine is not revving more. Tohatsu engines are very picky regarding transom height seated.

If you want combo boating perfection, place a mate up front, trim engine to be perpendicular to water level (90 deg) go for a wot spin, preferably on flat waters, pull your head out and check water flow at which lower unit height is passing by. If passing over small water deflector plate will produce unwanted transom water splashes and consequently will slow you down.

This is the perfect height set up for any Tohatsu engine. Wake is flat at center, check

http://www.youtube.com/watch?v=oBeZj...ature=youtu.be

Happy Boating

 

[bspyres]

No Title

yes prop test is good, 2 hrs no slip.
yes boat is 8ft.

Ok made it out on the lake again. played with trim a bit. if the motor is trimmed up i can get about 5100 WOT but have a really hard time getting it up on plane if i can get up at all, and that is just by myself. i also have about 2hrs on the tiny tach and i have noticed i burned a full five gallons of gas. i was told i should go all day on a tank, i was very suprized to run out., plugs are not black. here is a little video of the motor running.

is there any kind of hydraulic or remote trim for this motor?

http://youtu.be/w8towb12pgU

it still just doesnt seem like it is performing, i was on a patio boat with a 50 horse 5 people and a ton of gear that seemed like it had some good getup and go. but this thing full throttle just bogs..

thanks for more help
Barry

 

[Sea Rider]

Some issues :

A 2 stroke 30 HP engine burns near13% gal per hour of its stated HP. Engine height is not 100% perfect for Tohatsu engines, but almost close at the Sweet Engine Height, how does the combo performs at close tight turns at speed on flat calm no windy waters, are you experiencing light prop cavitation/aereation ?

If boat planes parallel with engine stitting perpendicular to sea level, you´re ok, no need to add a costly hydraulic trim onto engine. Overall vid speed looks fantastic. You're bit under rev with 5100 rpm, will need to go at least 2 less prop pitch sizes to dial near 5500 wot rpm, will have slight more top end speed. Plugs must be gapped tight to 1.0 mm, shim must not fall or pass loose through tip.

A 50 HP engine is + 700 CC. a 30 just 430 CC, that's why the great performance difference. Your boat is rated for max ? HP ? Is the aceleration even throughout the whole throtttle range, describe bogging at full throttle, engine misses, slows down ?


Happy Boating

 

[bspyres]

Thanks for all the great help Sea Rider!!

I guess i hadnt expected quite so much fuel burn on this little guy, that engine IS working its butt off.
As far as jack height, it is as it came from factory. it jumps and cavitates a lil, and on tight tight turns it will completely cavitate..
i dont really know where parrallel is on this boat.

1.) if the trim pin is 3rd hole from transom i can get on plane fairly quick maybe 5-8 seconds w me and small passenger but the bow dips and we take on lots of water once going. top speed is crummy maybe 4000 WOT
2.) If trim is 4th hole I can barely get on plane maybe 30 seconds if i can get on plane at all but if i do the boat rides pretty good and goes pretty quick. maybe 4800 WOT
3.) If trim is in 5th hole I can only get on plane by myself maybe 15 seconds and the boat goes really fast but porpoises a bit (which makes it fun) and ive seen as much as 5200 WOT also when trying to plane in 5th hole full throttle the motor seems to pull reasonably hard but then after trying for 10 seconds or so it seems to loose a little pep its just sitting there lugging. i tried pumping the fuel bulb to make sure the carb is getting enough fuel with no difference. I completely understand the need for a finer pitched prop helping with holeshot and getting WOT up, i just dont know if prop change is to compensate for some kind of engine issue that i dont want to mask. as this is also factory prop.

Thanks again
Barry

 

[Sea Rider]

Barry some tech issuess :

-An 8 footer is too small for a 30 HP engine. Assume boat has a very nervous behaviour with that power at speed.

-When boat floats alone, floats parallel to water level, it's called its natural floating position, should maintain same hull/water parallel level as if floating alone while boat is on plane at speed, only need to distribute your weight evenly on deck to achieve this condition.

-Static picture shows engine sitting at correct (90 deg) trim, but bit high for a Tohatsu, which is a natural born picky engine, that's why experiencing excessive aireation on tight close turns and definitely same while riding choppy & windy waters.

-If maintaining same 90 deg trim and moving your weight forward, should do well on flat straight courses, but expect aireation issues at close turns.

-If you move trim out of ideal 90 deg, will have more tail drag along best prop thrust loss, AV plate, prop shaft must ride parallel to water level to achieve the least LU drag.

-To stay at 90 deg and have that combo flying with a 30 HP will need to chop transom down at least 1" for water flow to skim under small upper water deflector plate which is the sweet engine/transom height spot for any Tohatsu engine.

-Will gain nothing switching to a lower pitch prop to as to increase engine rpm to where it should be revving, as this poor performer combo has a engine/transom height related issue, not a rpm issue.

On initial set ups it's a engine/transom optimization followed if needed by a prop maximization for best overall combo performance. Buyig a used combo is no guarantee previous owner has efficiently matched this particular engine brand to this particular boat brand. In this particular case definitely not....

Happy Boating

 

[4950cycle]

Is this a shear pin prop motor ? If so my mid 80s Tahatsu 30 came from the dealer back then on the same boat yours did. Even with same wings on lower unit yours have. Impossible to find a prop for. I modified an late 50s Johnson /OMC prop to get around this prob.