# 1989 4hp tohatsu issue



## oxbeast1210 (Jun 21, 2010)

I received a small boat in a trade with a 40 hp tohatsu 1989 model
the motor idles fine and runs to about half throttle but anything past half throttle doesn't increase speed the boat is going. It almost sounds like is gargling or wanting to cut out past half throttle.
I'm going to get fresh fuel and run some sea foam through it but i'm thinking it needs a carb rebuild idle and up to about half throttle it runs fine 
bogs at anything past half..

any ideas?
thank you


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## chicon monster (Mar 7, 2012)

Is the water pump working good.
My gamefisher did the same theing when the impeller disenegrated.


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## oxbeast1210 (Jun 21, 2010)

Yes the water pump is working fine strong stream coming out 
thanks


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## outbrdwrench (Apr 8, 2009)

compression check first, if good,cleaning the carbs is a good idea, and will probably fix it. dont forget about the gearcase oil, especially if you are unsure of its last service


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## oxbeast1210 (Jun 21, 2010)

thank you ill be sure to get a full service before really running just wanted to sort out the current issue . Ill be sure to get the gear oil done thanks
compression is 145 in both cylinders.
does it make sense to idle and run about half throttle ok but act funny after half throttle.?

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## outbrdwrench (Apr 8, 2009)

yes if the main jets are partialy clogged. how long has it sat for.


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## oxbeast1210 (Jun 21, 2010)

last owner said it sat about 3 months
he had it for about a year and only used it twice.

how fast should a 40 hp push an average 14ft boat? fiberglass

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## outbrdwrench (Apr 8, 2009)

probably about 40mph.


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## KingCrab (Apr 29, 2012)

outbrdwrench said:


> yes if the main jets are partialy clogged. how long has it sat for.


 yep, Sounds like a fuel issue to me.


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## oxbeast1210 (Jun 21, 2010)

thanks ill post an update once I go through it all
thank you

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## oxbeast1210 (Jun 21, 2010)

m40c is the model

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## oxbeast1210 (Jun 21, 2010)

ok so today I removed the carb and was surprized to see that everything looked clean and new.. the only spot I found gunk on was on the spot showen in the picture.
the hole ind the middle was completly clear but the area around it had alot of gunk on it I cleaned it up and blew compresed air through
it and it I can now feel it come out a jet at the front of the carb not sure what else I should do?

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## oxbeast1210 (Jun 21, 2010)

picture


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## oxbeast1210 (Jun 21, 2010)

Does anyone know what the orifice on the left is? brass with the little hole?
after cleaning the part that I colored blue earlier and blowing compressed air into i can now feel air coming out of that hole where before I couldn't feel anything .
:notworthy::notworthy:


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## drifterfisher (Oct 9, 2009)

Looks like a fuel jet,do ya have a torch tip cleaner? if so clean it with the closest size you can fit in there,and blow out with carb cleaner and compressed air. Let us know..


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## oxbeast1210 (Jun 21, 2010)

ok so after cleaning the carbs out I took it out today it ran a bit better but I'm still not gettiny full power.
I took the fuel pump apart and this is what it looks like....
also I checked the fuel water separater and it is really rusty I'm going to replace that too.
any other ideas??...

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## outbrdwrench (Apr 8, 2009)

after you replace that & ensure your tank/filter/hoses are good, make sure your throttle plate is opening completely.


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## oxbeast1210 (Jun 21, 2010)

yes sir I checked for that today it does open properly. I'm going to go ahead and replace the fuel lines and bulb aswell just to be safe. that should narrow it down more . I'm wondering if it could be an electrical problem but it idles and runs up to half throttle fine. 
thank you

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## outbrdwrench (Apr 8, 2009)

Not if its just a little down on power. You will probably fix it , that fuel pump diaphram is a little more than Toast.


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## oxbeast1210 (Jun 21, 2010)

Thank you for all your help I will update when the pump is in!


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## oxbeast1210 (Jun 21, 2010)

had the pump ordered just waiting for it now.

here is a quick clip u can tell its not getting full power

https://www.youtube.com/watch?v=QvsnThf3-W0&feature=youtube_gdata_player

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## oxbeast1210 (Jun 21, 2010)

that was full throttle looks faster in the video but it couldn't even get the boat to plane ..

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## Breeze (Mar 23, 2012)

oxbeast1210 said:


> that was full throttle looks faster in the video but it couldn't even get the boat to plane ..
> 
> Sent from samsung Galaxy note using Forum Runner


Usually what will clog up first in a carb is the pilot jet, which is used for idling up to bout 1/4 throttle. It has a much smaller hole in it so its normally the first thing to clog. You definately had some rust and crap in there, probably from water in the gas. That small brass orifice you showed on the end of the carb is the air jet.. it lets air pressurize the low speed circuit when the throttle plate is closed. That is not really going to affect your high speed performance.... That pump diaphragm definately looks bad though. If it bogs down, feels like it is just running out of power, thats normally a lean issue, not enough fuel and too much air.. that could be the carb or it could be the fuel pump not pushing enough pressure to keep up.... I got alot of carb experience so if you want to bring the carb by the shop I can look at it and make sure everything is clean as it should be..

As far as electrical goes... I have had two motorcycles, kawasaki's to be exact, that would not rev past half throttle... ended up being the ECM, or brain box. The ecm controls the timing and if it is not advancing the timing when the motor speeds up, the motor will not run properly at high speed. However, most of the time that will cause a popping and backfire issue, not a fall on its face kind of issue..

I would lean more towards that fuel pump then anything else.. or it could even be an intake leak leaning out the motor..


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## oxbeast1210 (Jun 21, 2010)

sweet thanks for all that info ill try the pump and see what happens if that isn the issue ill get with and maybe we can figure it out.
the rust and grime came from the fuel water seperator... gunna replace that too.

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## outbrdwrench (Apr 8, 2009)

while you are waiting for the pump, it wouldnt hurt to take that carb apart,since you know it now and soak it in superclean for about 4hrs. ENSURE everything is clean!! also inspect/replace all the hoses. that motor will take you fishing for years to come! BTW that was neat to have the footage, it would be nice to have that as part of the workorders at work.


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## oxbeast1210 (Jun 21, 2010)

Ok little update today I replaced all the fuel lines the fuel water separator and installed the new pump. Sounded great in the yard so took it out for a water test ran better then before but still have issues past half throttle . Goes good to half throttle then it just doesn't go more if anything it slows down . What do you recommend I Check next . What would cause a cylinder to drop at higher throttle but be fine at lower and idle speeds?
I may need to get some professional help soon...


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## drifterfisher (Oct 9, 2009)

Plugs? maybe a coil not up to par? Maybe the prop?


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## oxbeast1210 (Jun 21, 2010)

I was thinking ghe same things the plugs look brand new but ill replace them tomorrow how can I test the prop?

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## Breeze (Mar 23, 2012)

I was going to suggest plugs as well, I have had brand new out of the box plugs be no good... however I still think its a fuel issue.. Have you checked your float level? If its too low then there wont be enough fuel in the bowl to keep it running higher speeds... Have you tried running it with the choke on to see if its any better or worse? Also, with it running, you can spray carb cleaner around where the carb mounts to the engine... if the rpm's change then you have an air leak... an air leak could also cause the problem you are having......


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## Breeze (Mar 23, 2012)

Have you pulled the plugs? If so, what did they look like?


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## oxbeast1210 (Jun 21, 2010)

thanks for the tips breeze ill post some pics of the plugs. I did try applying the choke while at full throttle I got it about a quarter of the way out and it kill the motor and makes it hard to start for a while. I think it floods it....
I will try your suggestions today if I get a chance .
thanks Breeze

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## oxbeast1210 (Jun 21, 2010)

top plug

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## oxbeast1210 (Jun 21, 2010)

bottom plug

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## oxbeast1210 (Jun 21, 2010)

while mesing around with everything I pulled the plug cap off the wire. the wire was so corodded that when I grabbed it to try to clean some corrosion off the broke ...does anyone know where I can get this part locally in milton/ pace? 

its the piece on the right it was about an inch longer..

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## oxbeast1210 (Jun 21, 2010)

Took it out for more troubleshooting yesterday. still the same issue . We got the boat to run normal and plane out one time it was glorious haha . no but really it gave me some hope . The one time it planed we were slowly pulling the choke and one time it was just right we wouldn't repeat it again. If messing with the choke got it to work that means its more then likely still a fuel issue correct?

Today I took the carb apart and soaked it in cleaner then i blew compressed air through every corner . I put it all back together and will be testing it out again in about an hour.
O yeah the old fuel filter was leaking fuel it wouldn't seal so I went ahead and got a new one.


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## Breeze (Mar 23, 2012)

oxbeast1210 said:


> Took it out for more troubleshooting yesterday. still the same issue . We got the boat to run normal and plane out one time it was glorious haha . no but really it gave me some hope . The one time it planed we were slowly pulling the choke and one time it was just right we wouldn't repeat it again. If messing with the choke got it to work that means its more then likely still a fuel issue correct?
> 
> Today I took the carb apart and soaked it in cleaner then i blew compressed air through every corner . I put it all back together and will be testing it out again in about an hour.
> O yeah the old fuel filter was leaking fuel it wouldn't seal so I went ahead and got a new one.


Yea, if messing with the choke got it to run better, then its more than likely a fuel issue.. giving it choke richens it up, so normally if you give it a little choke and it runs better, then its a lean issue..


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## oxbeast1210 (Jun 21, 2010)

I don't wanna count my chickens before they hatch but I think I may have figured out the problem. Today as i was looking through the parts diagram i noticed that my motor was missing a part . I didn't think much of it at the time. Fast forward 5 or 6 hours and im in the water still having the same issue. I remembered that the part i was missing was 
345-02415-0 COVER, AIR SILENCER . So I decide to use my hand as a cover for the air silencer . Every time I did it it ran like it is supposed to! I didn't think a little part like that could cause the problem but it looks like it was. The air silencer still gets air from the top on the back and is designed to have the front covered . I'm going to order it and see what happens. I tried the choke and it kinda helped but not like putting my had over it...

what do you guys think ??


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## drifterfisher (Oct 9, 2009)

That will make it run different,it acts like a valve almost,something to do with the amount of suction and the pulse of the incoming air flow.


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## oxbeast1210 (Jun 21, 2010)

Great I hope thats what the issue is. well at least I know my fuel system is completely clean and new!


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## Breeze (Mar 23, 2012)

oxbeast1210 said:


> I don't wanna count my chickens before they hatch but I think I may have figured out the problem. Today as i was looking through the parts diagram i noticed that my motor was missing a part . I didn't think much of it at the time. Fast forward 5 or 6 hours and im in the water still having the same issue. I remembered that the part i was missing was
> 345-02415-0 COVER, AIR SILENCER . So I decide to use my hand as a cover for the air silencer . Every time I did it it ran like it is supposed to! I didn't think a little part like that could cause the problem but it looks like it was. The air silencer still gets air from the top on the back and is designed to have the front covered . I'm going to order it and see what happens. I tried the choke and it kinda helped but not like putting my had over it...
> 
> what do you guys think ??


Yes, that will make it do what its doing. I was going to ask about that but just took for granted it was there... sorry for that.. If its not there, the engine brings in too much air.. causing a lean issue.. which a lean issue is what I was suspecting from the start. I have had customers call me who did their own carb work and say their bike will not rev up, just falls flat off idle.. first thing I ask is if they got the air cleaner on there... makes a HUGE difference... You were sucking too much air and not getting enough fuel to compensate for it... Bet ya lunch that once you put it on there, the motor runs perfect... 

Big motors can run pretty decent without the air cleaner, but the smaller engines are very picky about those things.. Get it put on then enjoy the ride...


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## oxbeast1210 (Jun 21, 2010)

I hope that's the case breeze i really think it is. It was a good learning experience I know I have a brand new fuel system and clean carbs . Plus I learned a lot about my motor!
Soon as i get it running just right and have my trolling motor mounted . Ill take you with me to hit some grass flats !


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## oxbeast1210 (Jun 21, 2010)

sorry its sideways but that hole in front of the air silencer is supposed to be covered up witj a part that is missing on mine but its on the way!

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## Breeze (Mar 23, 2012)

Wish I had seen that picture before..... guarantee you thats the problem.. thats a massive hole letting in a massive amount of air....... Like I said in my previous post, I bet ya lunch thats your problem.... dont worry, McDonalds is fine with me... I am cheap.. LOL

Just for sh!ts and giggles, use duct tape and tape over that hole, then take the boat for a test run.. Then swing my McDonalds and bring me my lunch.... 

You can use duct tape to cover it and see if that cures the problem.. thats a quick easy temp fix for troubleshooting...


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## oxbeast1210 (Jun 21, 2010)

haha ill bring you a redfish or some trout instead . if I get a chance to test before the part is in ill truthe tape but more then likely the part will be in before I can go again.

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## oxbeast1210 (Jun 21, 2010)

finally got the part today have been cleaning it and getting it ready for trolling motor while i was waiting . hope to try it out later today or tomorrow to see if my problem is resolved .
I have high hopes that it will be .

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## oxbeast1210 (Jun 21, 2010)

she cleaned up well had some bad discoloring from the waterline down and he inside was very moldy. 
I need to save some money so babbster can bring back the shine

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