After my running around I can say without a doubt a merc prop won't fit on a tohatsu. So there must be some differences between the two.
new tohatsu outboard is this normal
- Thread starter katana750
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Thanks Katana, that is good to know. A lot of the dealers tell me the 3 brands come out of the same plant - obviously that is only part of the story. They basically say that Tohatsu manufactures all the under 30 HP motors for Tohatsu, Nissan and Mercury. However, sounds like they each have there own modified bits as well - very frustrating.
My motor is 20 years old and looking at the Tohatsu and Nissan parts books both brands, of that size and vintage, seem to have the same parts.
I tried the boat without the dingy and motor and hit over seven knots at just over half throttle my polaris is only eight feet and it had my 9.9 yamaha 2 stroke on it....I think with the short length and the weight at back it really digs in. In slows the yamaha down a full knot. So I think there isn't any power loss.
The mechanic talked to nissian or tohatsu dealer I'm not sure if there is a difference any way. He said the problem is with my boat. It vibrates at a harmonic frequency that matches the motor.....to telll you the truth he may be right. Every time I look at the motor it is very smooth but if I'm not looking at it I'd swear its vibrating right off the transom. It vibrated my magma grill right apart. To the mechanics credit he agrees something is going on understands my problem I left it with him he has an identical one he is working on that he can compare with in a tank. As I said he doesn't have a ton of experience with nissian but he is an autherized service guy and he general wants to find out if something is truly wrong. I put my old yamaha back on ....its the last day of the trip.....I must say I have a new appreciation it. The whole family is happy its back on. I really hope he finds some thing different in sound vibration levels between the two motors.....its going to be really hard to argue harmonics with nissian. I think if both motors sound the same and act the same its my boat.
If that's the case ill try another brand I guess and take a hit on the nissian. The first place I went to was a yamaha merc dealer at the other end of the lake when i couldnt reach the nissian guy. He didn't really think there was anything wrong with the motor. To his credit I was so frusted I would of bought a motor right then and there. He told me to hang on get the motor looked at if nothing came of it he wanted me to test one of his on my boat to make sure the price difference was worth it before he sold me something....its 2700 for the nissian against it looks like 4000 something for the yamaha. I'm just so far away from any dealership it makes it tough. Its not like I live in the sticks but sometimes it feels like it. If I want to buy a quad./ motorcycle/ snow mobile....I've got selection galore.....outboards I'm out of luck.
I mentioned the frequency thing before but generally that's going to happen at a given RPM. That is to say it will get excited at a specific frequency but would go away once you go above or below that. When you hit that frequency things will go through the excitement but as you ramp up, it should fade. Even then, I never heard of a good motor prop combo shaking the boat and making that kind of noise you describe.
It's like tuning my bass. As I get close, you can hear the frequency of the "wha-wha" increase or decrease as you stray from tune as com paired to another string playing the same note. At work, we use a shaker table to generate various frequencies, our stuff really dances at 30hz but at 50 it is like a rock. Everything has a natural frequency.
Maybe try removing the mount? It's too bad he won't mount that other one he's working on to see what happens if it's the same model.
It's like tuning my bass. As I get close, you can hear the frequency of the "wha-wha" increase or decrease as you stray from tune as com paired to another string playing the same note. At work, we use a shaker table to generate various frequencies, our stuff really dances at 30hz but at 50 it is like a rock. Everything has a natural frequency.
Maybe try removing the mount? It's too bad he won't mount that other one he's working on to see what happens if it's the same model.
My receipt shows it to be a Solas 4-blade high thrust prop, part number # 5013-087-05. Before I bought it I searched the interwebs and found a chart which listed the right part for my motor. I think I paid around $80, which was significantly cheaper than OEM. So far I'm very happy with the prop.
In my humble opinion one of the details that I didn't see addressed was going from a 2 stoke to a 4 stroke without changing the mount. Older 2 stoke mounts are normally narrower than 4 stroke mounts. They may still handle the weight but not the torque of the 4 stroke. The wider mounting foot print of the 4 stroke mount might be whats needed to absorb the torque and without it you get the vibration.
Also, can you try a comparison of the old and new OBs on the dingy? That might indicate whether it is boat related.
Also, can you try a comparison of the old and new OBs on the dingy? That might indicate whether it is boat related.
Thanks very much for that info SP. That adds up exactly to what I have been told in the past, so now I can go ahead and buy one without fear of blowing my money. Much appreciated.
Thanks Katana, that is good to know. A lot of the dealers tell me the 3 brands come out of the same plant - obviously that is only part of the story. They basically say that Tohatsu manufactures all the under 30 HP motors for Tohatsu, Nissan and Mercury. However, sounds like they each have there own modified bits as well - very frustrating.
Ya that was the impression i had as well. If I cant get this problem figured out Im going to look more closely at the differences because I only have two choices Yamaha or merc. Im going to stay away from the online route even if it means more money and a three hour drive.
To be fair I haven't talk to the people I bought the motor from but Im not expecting much but maybe ill be surprised. Ill try contacting Nissan as well maybe they will help me out. It would be nice if they didnt blow me off but really what do I say? the motor seems really noisy and vibrates my boat uncomfortably but the mechanic says there isnt a problem? Best case scenario would be for the mechanic to find something wrong. The motor runs great and doesn't visibly shake to the eye but man was everybody happy when the old motor went back on. For four days I tried to convince myself maybe its not that bad but after ten minutes at various throttle positions it was the same old thing.....what the heck is going on. If this is what four strokes are like there would be posts all over the internet ....I hate my four stroke I have to switch back....This is definitely not the case.
Ya that was the impression i had as well. If I cant get this problem figured out Im going to look more closely at the differences because I only have two choices Yamaha or merc. Im going to stay away from the online route even if it means more money and a three hour drive.
To be fair I haven't talk to the people I bought the motor from but Im not expecting much but maybe ill be surprised. Ill try contacting Nissan as well maybe they will help me out. It would be nice if they didnt blow me off but really what do I say? the motor seems really noisy and vibrates my boat uncomfortably but the mechanic says there isnt a problem? Best case scenario would be for the mechanic to find something wrong. The motor runs great and doesn't visibly shake to the eye but man was everybody happy when the old motor went back on. For four days I tried to convince myself maybe its not that bad but after ten minutes at various throttle positions it was the same old thing.....what the heck is going on. If this is what four strokes are like there would be posts all over the internet ....I hate my four stroke I have to switch back....This is definitely not the case.
I agree that would be the best way to determine what is happening but the outboard he has doesn't have a tiller and the remote steering has been cut off. On the plus side at least he has something he can compare side to side even if it just in the tank. If he says there isnt a problem I'm going to be out of luck. He did say he would try to co ordinate so I could be there.
The harmonic thing does seem like a long shot and yes it doesnt really change with increased throttle so I agree that doesnt make sense but who knows. It would make the most sense to me that there is an issue with the exhaust system, but I have no clue how that works on a outboard and the motor is very quiet at ldle and low rpms. I have zero complaints there but I'll be doomed to travel at 3.5 knots all the time.
Im sorry but I dont quite understand what you mean by removing the mount? I'll try anything though
Im game for anything but the motor is mounted directly to the transom on this boat. I could add plywood to either side but thats about it and it would have to be pretty thin it is already pretty thick There might be just enough room for .5 inch on each side but it would be tight. Just from following other posts I dont think other guys are modifying their transoms to accommodate the four stroke. There have been mods done but it seems it was more to increase the turning radius of the outboard
Sorry, I thought the OP said he had a motor mount. I was mistaken. I invisioned one of those brackets I see on other boats.
Not yet but I am seriously considering of putting one on. Maybe I could isolate the motor a bit more. Dont really want to.... the motor is kind of heavy and now im adding more leverage.
I guess ill have to wait for what verdict the mechanic comes back with and them go from there.
its brand new so I didnt want to fiddle with it too much but it did seem to push the boat and function just fine. It idled perfectly. It pushed the boat up to 7 knots pretty easy without the dingy. My best guess would be it was. It is about three hours away now with the mechanic. Im back at home. No point bringing it back with me....nothing would get solved from here. On a bright note I decided to leave the boat at the lake so I can go out for another trip next weekend.
I think as are all interested in seeing what the problem is and of course we want to see it resolved. It may be useful information at some point for someone else.
Me too. Ill keep you up to date.... Im just in a holding pattern. The easiest thing to have done would have just to try another motor but that seems a bit tougher than it should be. I dont think my expections of what the motor should be like are too high. The merc dealer and nissian apparently said the four stroke would vibrate more than a two stoke which would be fine I can fix the rattles but when the noise level is so loud you have say what all the time.....it drives me nuts... and every where I look I see the words smooth and quiet. Sure if your previous motor was a british seagull maybe but I cant be the only guy that has gone from a 90's two stroke to a four stroke. Its such a huge gap in comfort level.....I dont think anybody would switch.
I should probably think more positively and maybe something is wrong but I think it will be tough to diagnose and tougher to prove. If I was a gambler I could buy another Tohatsu just to see. I would still have spent less money than if I bought a yamaha. I have seen them much cheaper online but then I havent learned my lesson. The merc/yamaha dealer was very good and I that is worth something for sure.
I should probably think more positively and maybe something is wrong but I think it will be tough to diagnose and tougher to prove. If I was a gambler I could buy another Tohatsu just to see. I would still have spent less money than if I bought a yamaha. I have seen them much cheaper online but then I havent learned my lesson. The merc/yamaha dealer was very good and I that is worth something for sure.
I definitely thought about it but I thought I better not mess around with anything. I have some mechanical knowledge with engines but Im not even close to an expert. The motor sounds just like a one cylinder air cooled motor or a really cheap air compressor. They both work but you want to hide them behind the truck and run a long cord so you dont have to listen to them.
Just a quick update for the people that were following this thread...I dont really have any news about the outboard yet. The mechanic has run it in a test tank but hasnt had a chance to fix the remote controls on the other Tohatsu so he can compare. He thought it was a bit loud but wasnt sure. I have talked to Nissan. I have to say they were very easy to talk to and said they have had vibrations complaints before but never anything about the noise. I said he would even listen to it over the phone for me but he said it was best if they worked with the mechanic. Unfortunately being three hours away I just have to be patient but his point does make sense
I was trying to figure out how to quantify my feeling that the motor was too loud. I started looking around the internet for db meters and realize they make free ones for smart phones....I would have never thought of that....anyway I downloaded one and gave it try. I'm not sure of its exact accuracy but it seems quite sensitive...In any case it gives me reference point. We went to the lake last weekend and tried it out. Sitting in the cock pit and in the cabin we were looking at 69/70 decibels. 60 is said to be normal speach. Wide open held up to the cowling on the 2 stroke Yamaha it was the low eighties. I was just wondering if anybody else has ever tried this with their motor.
At the marina we were looking at the other sailboats. A good portion of them have motor mounts. So that got me thinking maybe it would be a such bad idea to mount one on the boat. It would be fairly easy to isolate the motor and connection points with rubber mounts and I would have full range of motion with the motor. This would be a big bonus. I guess the down side would the motor would be harder to reach and the increase leverage on the transom but that could be beefed up a bit and I dont usually trailer the boat with the motor on anyway.
In the mean time I just wait.
I was trying to figure out how to quantify my feeling that the motor was too loud. I started looking around the internet for db meters and realize they make free ones for smart phones....I would have never thought of that....anyway I downloaded one and gave it try. I'm not sure of its exact accuracy but it seems quite sensitive...In any case it gives me reference point. We went to the lake last weekend and tried it out. Sitting in the cock pit and in the cabin we were looking at 69/70 decibels. 60 is said to be normal speach. Wide open held up to the cowling on the 2 stroke Yamaha it was the low eighties. I was just wondering if anybody else has ever tried this with their motor.
At the marina we were looking at the other sailboats. A good portion of them have motor mounts. So that got me thinking maybe it would be a such bad idea to mount one on the boat. It would be fairly easy to isolate the motor and connection points with rubber mounts and I would have full range of motion with the motor. This would be a big bonus. I guess the down side would the motor would be harder to reach and the increase leverage on the transom but that could be beefed up a bit and I dont usually trailer the boat with the motor on anyway.
In the mean time I just wait.
FYI, the one spot where I had a vibration issue was between the inner forward wall of the Laz and the back outer wall of the cabin area. Its an outer liner flat area right next to an inner liner flat area and mine would resonate with the outboard. I added a few additional fasterners (ss bolts, fender washers, nylon nut) between the two glass parts.. this made a signicant differnce
The best picture I can find is below - I put the extra fasteners just behind and also slightly above the red gas tank..
The best picture I can find is below - I put the extra fasteners just behind and also slightly above the red gas tank..