tohatsu 40c I think it should have more power

[jwilkey84]

I have a tohatsu 40c that I rebuilt the carb on last summer. It runs great as far as the carbeurator goes, but I wonder if it should have more power. I also have an evinrude 25 and it doesn't seem like the 40c has much more power than the 25. There is a possibility that the previous owner let the engine overheat, would that cause it to lose some of it's power? If so what should I do? I also read in a different resoponse that the engine should have the same "feel" shifting from neutral to forward and to reverse. Usually my engine shifts fine into forward but it almost always grinds going into reverse. It also helps if the engine is at a very low idle when shifting to reverse. Any ideas on getting more power out of my 40c? Also I can get the motor to wind up more rpm's in neutral than I can when it is in gear. Is that normal because there is no resistance from the water when the prop isn't turning?

 

[TOHATSU GURU]

Re: tohatsu 40c I think it should have more power

The 40 should smoke that 25. If it overheated you need to get it into a dealer to have it checked out. If the engine is having trouble going into reverse it probably has a clutch or reverse gear problem. There are many things you can do to get more out of the 40 C. Do a search on "Sport C boat racing). It's normal to have more RPM in neutral.

 

[John_S]

Re: tohatsu 40c I think it should have more power

What size boat and what diameter and pitch for prop? I get just over 30mph on a 14' modified V alum starcraft, with 2 people. I am running the old style Hustler alum prop - 10 7/8" x 11" pitch. I tried a 12" pitch and got a little more topend, but it was more sluggish out of the hole, especially with 3 people.<br /><br />BTW, we use to have a 1977 Johnson 35hp on this boat. The 40C outperforms it in hole shot, topend, and reliability.

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

My boat is a 14' aluminum vbottom. I have no idea about the prop. Which prop would be the best for me? Is there a possibility that I might need a new piston??

 

[John_S]

Re: tohatsu 40c I think it should have more power

Is there a possibility that I might need a new piston?? <br />

Do a compression check. Otherwise it would need to be tore down and inspected. Why do you believe it was overheated? Paint discolered on the powerhead?<br /><br /><br />

I have no idea about the prop.

If it is the stock prop, it has a number on it which will ID it.

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

What would be a good compression to have? I dont know what is good and what is bad, but I do have access to a compression checker

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

I think it might have been overheated because the previous owner told me when the water pump went out they were on the water. He said they just kept driving the boat anyway, stopping along the way until they got to shore. The problem is, I dont know if they stopped and shut off the engine or if they just let it get so hot that it shut off by itself. The motor runs great, I just think it should have a lot more power than my 25hp. could my carb be adjusted incorrectly?

 

[John_S]

Re: tohatsu 40c I think it should have more power

I will check my manual, this evening, and post back on the spec. BTW, highly recommended to get one. Even the Clymer's multi-hp model book is OK. You will need for tune-up how-to, anyway.

 

[John_S]

Re: tohatsu 40c I think it should have more power

Book says 107psi, no tolerance listed, but both cylinders need to be within 10% of each other.

 

[ziemann]

Re: tohatsu 40c I think it should have more power

thedammit-<br /><br />I suspect this is a simple problem. You say it runs fine (other that the gear grinding). Your performance issue is most likely a prop issue.<br /><br />The 40C has always been a very strong engine. Usually, people complain that they can't tell difference between the 40 and the 50. There is something amiss.<br /><br />You need to make sure it is propped to reach peak RPM. The problem you are describing to me sounds like it could be something basic like poor propping. Just because you bought it from someone else doesn't mean that it is propped right. <br /><br />Buy a service manual from Elvin. It is well worth it's weight in gold.

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

The gear grinding really isnt a big issue. If I just shift to reverse hard and fast it will go in 90% of the time. So maybe the prop is the issue. I mean it idles fine, runs great, has quick response........I just think it should go faster. I have downloaded a manual for the 40c from the Tohatsu webpage. Is that a sufficient guide? I think it is about 50 pages or so.

 

[TOHATSU GURU]

Re: tohatsu 40c I think it should have more power

Your lower unit is already damaged. Continuing to use it will only make it worse. Take the lower unit apart and see what is wrong.

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

I dont mean to sound so dumb, but what could be wrong in the lower unit? I am totally in awe now. I have an engine that runs fine I just thought should have a little more power, and now it has all kinds of possible problems. I will do the compression check and see how that turns out. I like all of your help elvin, but it's like I went to the doctor because I thought I had a cold, and I left with pneumonia. Thanks for the help, but I seriously hope that you are wrong, I have never had the lower unit apart. I've rebuilt the carb and took off the lower part of the motor to check the impellor once, but do you think I can handle the lower unit?

 

[TOHATSU GURU]

Re: tohatsu 40c I think it should have more power

The three gears and the clutch are designed to fit together smoothly. If there is a problem where the engine does not go into gear 10% of the time....Then something has gone wrong. It could be that one or more of the gear teeth have sheared, that the engagement blocks on the gears and clutch are damaged or that the shift linkage is way off. But if you don't repair it it will only get worse and more expensive. Think of it like this:<br /><br />Lets say you pee ten times a day. If one out of every ten times you pee blood....Would you ignore it or would you go to a doctor?

 

[John_S]

Re: tohatsu 40c I think it should have more power

thedammit,<br /><br />1) Buy a service manual.<br />2) Check/adjust shift linkage. (this is probably in the operations manual you downloaded)<br />3) Set idle, check/time engine.<br />4) Now see if it still grinds. No -great! Yes- review manual and see if you want to do this repair or send to outboard mech.<br /><br />No matter what, buy a service manual!

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

Let me clear up a previous statement of mine. When I said it goes in 90% of the time, I meant it goes in 90% of the time with no grinding. It always goes into gear, it just grinds if you dont do it in a quick firm motion. And when it does grind it is for like a 1/2 second. Do you still think it needs to be taken apart? Perhaps the linkage needs adjusted? But I am definitely getting a manual. The manual I downloaded isnt very helpful. Hopefully the real manual will be more help.

 

[TOHATSU GURU]

Re: tohatsu 40c I think it should have more power

That's a little different. The gearshift selector is designed for you to snap the engine in and out of gear. If you ease it in and out of gear the facings on the clutch and gears are grinding on each other before they fit into place. You may not have a problem at all. Z-Man MT makes a valid point about the correct prop being important. If you have a prop pitch that is a little low you can go to one a little higher and pickup more top end speed.

 

[jwilkey84]

Re: tohatsu 40c I think it should have more power

I feel a lot better!! Sorry for the confusion.I did buy a manual from internet outboards, how long should it take to get to me in Iowa? I will have to check out the prop, I assume it is stamped somewhere? Any recommendations, Elvin, on a prop size for the 40C on a 14 ft aluminum 2-3 man fishing boat? I do have some of those planer boards on and it seems to have plenty power out of the whole and plais fairly quickly.

 

[TOHATSU GURU]

Re: tohatsu 40c I think it should have more power

Usually three to five days. The prop will have a letter code or a number stamped onto a blade on the body. Prop selection is educated guess work. Knowing what you have now is going to be the key for better selection. If you can lose some takeoff power, then go up one pitch size.

 

[ziemann]

Re: tohatsu 40c I think it should have more power

thedammit-<br /><br />Elvin is by far the authority here on Nissan/ Tohatsu. Essentially what he is saying is that this is an outboard that by design is very solid with virtually no quirks. If your outboard isn't smooth, then there is probably room for improvement. If the quirks you are experiencing are not a big deal, then use it and enjoy it. But, from the sounds of it, it could use some fine tuning. 40's should be very smooth on the shift. A firm smooth motion when you shift (at idle) should cause it to shift with no grinding. A slow or partial shift will cause what you are describing. <br /><br />Now to the prop. I don't know where you live in Iowa, but research to see if there is a prop shop close by. Often times, they will assist you in seeing if you have the right prop for your boat. I ran into a problem with propping by using my Nissan 50 TLDI at 4500 to 5000 ft. in the mountains. I found a prop shop and the owner was nice enough to give me several props to try trial and error to tune it to get the max RPM. I found the one that worked the best and bought it and returned the other two. Like Elvin implies, props are often trial and error to get the perfoect one for your boat, weight, hull type, horse power, etc. Usually, we can get you close, but it takes some fine tuning from there. For me, getting my Nissan TLDI propped perfect at peak RPM gave me a few mph on top and pushes my very heavy Smokercraft 16.5' at a healthy 33 mph. <br /><br />If you are not real familiar with outboard mechanics, then sometimes the advice to seek a good dealer is worth heeding. But, if you choose to work on this outboard, you will not find an easier modern outboard to work on. <br /><br />You ask good questions, and by the way, welcome aboard.