Just because the engine came off a bigger boat does not mean it had the correct prop. Look for a part number on the prop. The best prop will have a smaller dia hub than the gear case, that is the smallest pitch prop.
Do the mounting brackets have 3 or 4 choices for engine height? The newer 70 had these type of brackets with several height adjustments.
Sounds like the hull could be twisted and hooked.
Try getting the boat as leval as possible side to side and then check how leval it is every 12" from transum, shoud be the same at each location, if not hull could be twisted.
Call me if it helps you, 832 473 8928
Boat Rolls at speed
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John - thanks for the info and offer to talk. The engine is being worked on, so I do not have the boat here to check on your questions. Hopefully I will have it in about a week. I did a lot of work on this hull and did not notice any twist. I am going to attempt to post a few photos that might tell you some things about the hull and outboard. Thanks again!
Pictures are worth a thousand words, your engine has a heavy duty gear case for heavy loads and slow speeds. They were first used on 58 and 59 50 hp engines. They were noted as gas hogs and slow, but a lot of power. Prop torque could be the problem! You are out of my field of direct knowledge, however it is my best guess. Heavy duty gearcase uses a 13 dia prop and the high spped std gearcase uses a 10 inch dia prop!
Good news is there are a lot of std gear cases, that will bolt right on your mid section. You can also very easily put of any OMC 1960 to 1968, 60,65,75,80,85 or 90 to see if that is the problem. That is as long as it is not the heavy duty gear case you have. Engine swaps are very easy! Or put back on your newer 70HP.
I would find a std duty gear case reguardless, as top speed will increase maybe 5 to 10 mph with an increase in fuel economy.
Here's a link with both gearcases. http://www.old-omc.de/e_1966/seite_08_09.jpg
You realy need to check top rpm, the prop looks like it has a lot of pitch, less pitch may help, but I would change the gear case, which will lower the available torque.
Very nice job on boat, engine is very nice also, worth the effort to find a solution, if you were in Houston we could find a solution in less than an hour, or at least determine what is happening. Are you coming to the meet in Wis in June?
Good news is there are a lot of std gear cases, that will bolt right on your mid section. You can also very easily put of any OMC 1960 to 1968, 60,65,75,80,85 or 90 to see if that is the problem. That is as long as it is not the heavy duty gear case you have. Engine swaps are very easy! Or put back on your newer 70HP.
I would find a std duty gear case reguardless, as top speed will increase maybe 5 to 10 mph with an increase in fuel economy.
Here's a link with both gearcases. http://www.old-omc.de/e_1966/seite_08_09.jpg
You realy need to check top rpm, the prop looks like it has a lot of pitch, less pitch may help, but I would change the gear case, which will lower the available torque.
Very nice job on boat, engine is very nice also, worth the effort to find a solution, if you were in Houston we could find a solution in less than an hour, or at least determine what is happening. Are you coming to the meet in Wis in June?
John - Thanks so much for the insight. It is definitely worth trying the std gearcase with the smaller dia prop. I've already checked with my outboard mechanic, and he seems to think he has what he needs to do this, and agrees it is the right thing to do regardless of whether the change solves the roll problem. When we test drove the boat, it jumped onto a plane, even trimmed fully up, and topped out at 30 MPH (leaning left hard). It may well be that instead the engine power efficiently pushing the boat forward, some of the horsepower was causing the boat to roll. I'll know for sure in a week or so when he is done with the engine. I'll let you know.
Thanks for the comments on the refinishing. I enjoyed working on the boat and it came out better than I originally thought. Unfortunately I cannot make the trip in June due to a business conflict.
Thanks again. Rich
Thanks for the comments on the refinishing. I enjoyed working on the boat and it came out better than I originally thought. Unfortunately I cannot make the trip in June due to a business conflict.
Thanks again. Rich
John, you have a good eye! I too spotted the split gear case and wondered "what's with that". I did not know about the heavy duty drive.
Rich, does your motor have mechanical or electric shift? That will be an issue when looking for a replacement lower unit. Your mechanic should know about such things.
Joe B
Rich, does your motor have mechanical or electric shift? That will be an issue when looking for a replacement lower unit. Your mechanic should know about such things.
Joe B
Joe
The heavy duty gearcase was only offered in mechanical shift and was last offered in 1968 as an option on the 65 and 85 . In 1969 thru hub exhaust gearcases were the only option.
It is the same basic gearcase as the 1958 and 59 50 hp.
Way back then, I was a factory certified mechanic for Evinrude. I worked my way thru school as a outboard muchanic. Started in 1965 at the age of 14 thru undergrad school.
Before grad school I worked 19 months as a R&D engineer for Mercury Marine on the V6 Black Max, in addition to 2 summer as an engineering intern at Mercury during undergrad school. My major assigment at Mercury was handling and stability as it related to chime walking, on the Black Max.
I also claim the idea of prop porting, I discovered while wroking on the V6 Black Max.
My senior engineering design project at Texas A&M, was a 4 way power trim, or as it is called today, Jack Plate. I built the first one at Mecury to research how engine height related to crime walking and steering torque. I used it to demonstrate the importance of correct engine height, when I was a engineer helping boat manufactors set up the Black Max on their new boats. Within 6 months, jack plates became available to the public.
The heavy duty gearcase was only offered in mechanical shift and was last offered in 1968 as an option on the 65 and 85 . In 1969 thru hub exhaust gearcases were the only option.
It is the same basic gearcase as the 1958 and 59 50 hp.
Way back then, I was a factory certified mechanic for Evinrude. I worked my way thru school as a outboard muchanic. Started in 1965 at the age of 14 thru undergrad school.
Before grad school I worked 19 months as a R&D engineer for Mercury Marine on the V6 Black Max, in addition to 2 summer as an engineering intern at Mercury during undergrad school. My major assigment at Mercury was handling and stability as it related to chime walking, on the Black Max.
I also claim the idea of prop porting, I discovered while wroking on the V6 Black Max.
My senior engineering design project at Texas A&M, was a 4 way power trim, or as it is called today, Jack Plate. I built the first one at Mecury to research how engine height related to crime walking and steering torque. I used it to demonstrate the importance of correct engine height, when I was a engineer helping boat manufactors set up the Black Max on their new boats. Within 6 months, jack plates became available to the public.
Too hard to tell from photo, but it is a 20 inch engine on a 20 inch boat. The mounting brackets that are best to use, have 4 holes about 1/2 apart to fine tune your engine heigth. In most cases not necessary, but nice to have. These brackets are a direct exchange for the ones you have, can not tell by picture, if yours have 4 holes you already have them.
Correct transum heigth is only a guess, and depends greatly on prop used. Best guess for yours is all the way down. I'm assuming your goal is handing, not absolute top speed. Our boats seem happest at about 15 to 20, maybe 25mph!
If you have not, click on my picture link below, number 35 shows my boat running 41.3 mph with a 1960 Envinrude 75hp!
Correct transum heigth is only a guess, and depends greatly on prop used. Best guess for yours is all the way down. I'm assuming your goal is handing, not absolute top speed. Our boats seem happest at about 15 to 20, maybe 25mph!
If you have not, click on my picture link below, number 35 shows my boat running 41.3 mph with a 1960 Envinrude 75hp!
Update - I was able to find a 1965 75hp Evinrude with a standard gear case locally which I traded for the Johnson with the heavy duty gear case, and the boat roll problem is gone. Prop torque was the biggest problem as John predicted.
The replacement engine has the smaller diameter, 10" pitch prop. Top speed is in the low 30s based on the boat speedometer, which is faster than I need to go. I did not have a gps with me. The slight hog in the bottom is causing the boat to ride very flat at full throttle, even trimmed all the way out. The nose is not diving and the handling/steering is steady, so I am ok with it for now. The trailer has been corrected to support the transom in order to keep the hog from getting any worse.
Thanks again for all your help. It was very valuable!! Time to enjoy the boat.
The replacement engine has the smaller diameter, 10" pitch prop. Top speed is in the low 30s based on the boat speedometer, which is faster than I need to go. I did not have a gps with me. The slight hog in the bottom is causing the boat to ride very flat at full throttle, even trimmed all the way out. The nose is not diving and the handling/steering is steady, so I am ok with it for now. The trailer has been corrected to support the transom in order to keep the hog from getting any worse.
Thanks again for all your help. It was very valuable!! Time to enjoy the boat.