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Author Topic:   Katama 16 and 135-HP V4

geordybass posted 11-07-2009 10:16 PM ET (US)
Hi guys! I'm new to this forum and wanted to say: I recently got a 1969 Boston Whaler Katama model and a 1994 40-HP Yamaha Precision Blend outboard. Well, 24- to 26-MPH was my top speed. I recently put the engine up for trades on the paper and some guy wants to trade me a 1976 Evinrude 135-HP V4. It's the same as the 85hp and 115 so it weighs about 300-lbs with power trim, about 100-lbs less than a 75-HP four-cycle engine. I dont think weight will be too much of a [concern] since the console is counter balancing as well. But does anyone think I am very overpowered? I know how to navigate pretty well with some years of experience and wont put the throttle down too hard because local California lakes have a 35-MPH speed limit anyways.
brisboats posted 11-08-2009 05:10 PM ET (US)
The 135hp is a very strong engine and while it may weigh the same it is a very different engine than an 85hp. Boat will be overpowered but if used with prudence would be fine. I have run 16'7" hulls with 135-140hp v-4's and they are stable until around 50 mph after that a handful. What you are not going to like is the gas consumption, the 76 engine probably is manual trim too. The early OMC v-4's had high compression heads and really should be run on premium gas.
A good running 70hp will get you to 35 mph and save a lot of fuel. Unless this 135hp seems to be your only option. I would hold out for a lighter 3 cylinder 70hp to come along or even a 85-90hp. There is plenty of them around and it seems better suited for your intended use.
Brian
geordybass posted 11-08-2009 09:24 PM ET (US)
Thanks bris boats! The motor has power trim and tilt on it. Compression on it is 115-120 even. I will usually be running at under 40-MPH, and my guess is that lower RPM means less gas consumption. I won't really ever full throttle it as I'm scared of tipping. I will be usually just fishing around in the harbors and channel islands in California.
Do you think it will suit my purposes or will I be dissapointed? I'm not really looking to race anyways, just have more power than I need just in case :-)
brisboats posted 11-09-2009 10:38 AM ET (US)
Sure it will suit your purposes. The motor will use less gas if you keep out of the throttle. Still not going to be as efficient as a smaller motor though. Trouble is that when driving around a hot rod it is hard to stay off the gas. The 135hp is just a souped up version of the 115 hp. The motor has higher compression heads (looks like yours has been lowered), bubbleback exhaust, intake stuffers, bigger carbs, different timing, etc. to make the 20hp gain. The horsepower is made in the upper rpm range so yes if you stay away from that upper rpms it will be much like driving around a lower horsepower engine.
Sounds like you have already have made up your mind. If not ask the previous owner when the last time the thermostats were changed. That motor is a bear to do.
Brian
Tohsgib posted 11-09-2009 12:20 PM ET (US)
I guarantee you will fetch more $$ from a 1994 40-HP Yamaha than a 34-year-old OMC. I would sell the Yamaha for at least a grand, maybe $1400 and look for a nice 60 to 90-HP. If you get a Yamaha, you can keep your rigging which is what I would try and find.
pcrussell50 posted 11-09-2009 03:45 PM ET (US)
Nothing super constructive to add other than that I have a 1975 V4 135hp myself. It's on another boat, a light 16 footer with a performance hull that is designed for higher speeds. It has been very reliable over the year that I have owned it.
Peter
Santa Barbara, CA
geordybass posted 11-09-2009 04:14 PM ET (US)
The Yamaha engine's lower unit was shot. And my motor is a flatback so no bubble. I can control it though have been around boats a lot so I know the deal.
Should I get a bigger gas tank? I have three 6-gallon tanks. Is that enough? And I like that motor more because as the RPM are lower at cruise I would think that it would be pretty much more fuel efficient than a 70-HP.
Kinda comparing it to my old truck and new one. I get about 22mpg on my [2006] Tundra V8 and I used to get about 19 on my 2002' Tundra V6. Apples to oranges yes
Thanks for bearing with me guys! And how fast is the max speed this motor will be pushing?
brisboats posted 11-10-2009 05:31 PM ET (US)
A hot 135hp should get in the low to mid 50's. But no such thing as a flat backed exhaust 135-HP. Looks like what you may have is a 115hp with a 135-HP cowl. Whichever motor it is, it is not going to be more efficient than a 70hp, even at cruise. A crossflow v-4 115hp or 135hp can go through those three 6 gallon tanks in an afternoon with relative ease. I would run an 18 gallon under my rps and an extra 6 gallon just in case when running one. Even a 2-3 hour easy afternoon cruise always burned off at least 12 gallons more often than not the 18 gallon tank was spent. The motor at idle is very thirsty too.
Brian
pcrussell50 posted 11-10-2009 11:03 PM ET (US)
My 1975 135hp V4 crossflow burned 10 gallons on a 30 mile round trip this past September. That was in a lightweight, 16 foot performance hull, bass boat-like proportions, running at 5,800-RPM most of the way, but throttled back, because the prop is not coarse enough for a lightweight boat. Just a data point for you.
I'd have better mileage figures for you, but most of the time I run her for about 5 minutes, to our favorite cove, swim, sunbathe, fish, and then 5 minutes back to the dock, where I send the wife out to get the trailer and I make a couple of speed runs by myself. On those days, I only burn about a gallon and a half for the whole day.
Peter
Santa Barbara, CA
jimh posted 11-11-2009 08:55 AM ET (US)
The fuel efficiency of a motor, that is, its brake specific fuel consumption, generally is best when the motor is running with about two-thirds to three-quarter throttle and with at least 50-percent load. Running a more powerful motor at lower throttle and lighter loads generally results in worse fuel economy.
adlert posted 11-11-2009 10:58 AM ET (US)
To add to JimH's comment, cruising with a cross-flow engine such as the 135 hp will definitely not be as efficient as cruising the same speed with the more efficient loop scavanged 3 cylinder engine.
Tohsgib posted 11-11-2009 11:36 AM ET (US)
Get the model number. 135's should be bubbled.
pcrussell50 posted 11-11-2009 03:13 PM ET (US)
Yes, Jim. My 3mpg with the v4 135 was at high rpm and light load under part throttle. If I had had the right prop, I could have run less rpm, more throttle opening, and higher load... putting me in a more efficient spot in "the envelope".
FWIW, I agree with the others that if fuel consumption is an important criterion for the OP, he's better off with the smaller displacement motor with the appropriate power rating. That said, not all of us have that concern. My typical boating day consists of about 2-5 miles of distance covered so even my 135hp v4 at 3 mpg won't be putting me in the poor house.
Peter
Santa Barbara, CA
geordybass posted 11-11-2009 03:46 PM ET (US)
Hey, the model # is 135643... but the cowl says 90hp... I'm kinda confused but the model # is for a 1976 135hp Evinrude. Lets say the powerhead was 90 or 115 does that maybe decrease the fuel consumption?
brisboats posted 11-11-2009 05:16 PM ET (US)
Simple answer is yes but not much. The 135's have the "tight" heads resulting in higher compression numbers than you posted. Higher compression engines are generally more efficient. 135's also are able to flow more exhaust through the bubbleback exhaust housing. It looks like you have a 135 midsection with a different power head, likely a 115hp. Not a huge difference in gas consumption between the two but no where near where you would be with a loop scavenged 3 cylinder 70hp as myself and another poster have said. Looks like you own it already so bolt it on and post some numbers. A good running 90hp or 115hp with power trim on that hull will provide plenty of speed.
Brian
pcrussell50 posted 11-13-2009 04:05 PM ET (US)
brisboats sez:

quote:
The 135hp is just a souped up version of the 115 hp. The motor has higher compression heads (looks like yours has been lowered), bubbleback exhaust, intake stuffers, bigger carbs, different timing, etc. to make the 20hp gain. The horsepower is made in the upper rpm range so yes if you stay away from that upper rpms it will be much like driving around a lower horsepower engine.
I have had a '75 135 v4 xflow for a year now and have been delighted with it. So much so, that I've pretty much taken it for granted, but now reading these threads, I'm starting to learn about it. I now know what the "bubbleback" is. I also didn't know about the high compression heads. Do you think 91 pump is enough octane? That's what I've been using, but I can start to mix some 100-113 octane race fuel in there if 91 is too sketchy. Also, what are "intake stuffers"?
Peter
Santa Barbara, CA
brisboats posted 11-14-2009 11:10 AM ET (US)
Peter, The OMC 135hp is not a motor to take for granted. On a Montauk hull it is faster than the coveted mercury prop rated 115hp inline six that gets a lot of press here. The early motors like yours were made to run with the better gasoline of the time. Later OMC lowered compression and even had thicker head gaskets to use the poorer quality fuel of the mid 1980's. If it were my motor, I would want to run 92 octane or higher and make sure the timing was set at 25-26 degrees not the 28 some motors called for. Crossflows are prone to coking the rings so it is imperative that the timing and gas be right. Do a compression test on your motor too as it may have had the heads or gaskets changed out to run on regular pump gas.
Intake stuffers are simply intake filler blocks used to create better airflow. OMC used them to create more horsepower on the 135's and 140's. The 140hp came along in 1977 I believe and used an additional modification to the lower exhaust web between the two bottom cylinders to attain the extra 5hp. This cut can be easily made if the engine is apart. The 140's also used diverters in the cylinder heads to redirect the water flow not for better cooling. I am not sure if the 135's had those.
At any rate this is a case where the factory took a 115hp motor and added a few well thought out modifications to achieve the extra reliable 20hp. The 135's were factory hotrodded 115's, the higher compression and unlimited powerpack creates a crisp revving motor that will turn 6000 rpms or more and still stay together for a long time. The bubble back exhaust is machined to match the block and creates a much better flow, many would argue that most of the horsepower gain is attained by the bubbleback. Hope you enjoy yours and it continues to provide thrilling and reliable service.
Brian
pcrussell50 posted 11-14-2009 04:05 PM ET (US)
Now THAT was a hell of a good answer. Thanks.
Funny. Way back before I bought this motor, the previous owner started it up on the muffs while he was demonstrating it to me. It recall thinking how raspy and crackly it sounded. I am an amateur auto racer and and I build my own race engines to help defray costs I recall thinking when I first heard that 135 how it sounded like a high compression motor... that was was waaay before I actually knew that it was.
Peter
Santa Barbara, CA
L H G posted 11-15-2009 02:55 PM ET (US)
Brian, your statement caught my eye. On the 1974 Evinrude 135, powerhead rated at 135HP, what would be the prop HP?
I have been told the later Merc 115 Towers were actually putting out 125 at the prop. I find it hard to believe the old OMC 135 did any more than that.
I ran a 1973 powerhead rated Merc 150 Tower on my 1971 Nauset for 11 years. A screamer!
With any of these engines of this power, I think a stand up console configuration in an old 16 is mandatory for safe WOT operation. From my experience with the Merc 150, I would not want to be sitting down.
brisboats posted 11-15-2009 07:11 PM ET (US)
Peter, Your welcome. Please do a compression test and let me know where it is. The last 135hp I had I sold to a nice member here and it tested 150psi on all four with my mac gauge. Wow! Crisp and raspy to say the least.

Larry, I have never dyno'd one but would guess you are right probably around 115-125hp same as the adi inline sixes like yours. Where the V-4 wins in my opinion is torque and there is even more potential remaining inside the motor from a tuning perspective. The 1985-1988 adi inline sixes had already achieved all Mercury could do with that motor. Power to weight the Mercury wins and on a lighter hull might even be faster.
Didn't you once say that your Nauset with the 150hp was no match for the OMC 135's of the day? ;-). Yes, definitely no sitting down with either motor.
Brian

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Author	Topic: Katama 16 and 135-HP V4
geordybass	posted 11-07-2009 10:16 PM ET (US) Hi guys! I'm new to this forum and wanted to say: I recently got a 1969 Boston Whaler Katama model and a 1994 40-HP Yamaha Precision Blend outboard. Well, 24- to 26-MPH was my top speed. I recently put the engine up for trades on the paper and some guy wants to trade me a 1976 Evinrude 135-HP V4. It's the same as the 85hp and 115 so it weighs about 300-lbs with power trim, about 100-lbs less than a 75-HP four-cycle engine. I dont think weight will be too much of a [concern] since the console is counter balancing as well. But does anyone think I am very overpowered? I know how to navigate pretty well with some years of experience and wont put the throttle down too hard because local California lakes have a 35-MPH speed limit anyways.
brisboats	posted 11-08-2009 05:10 PM ET (US) The 135hp is a very strong engine and while it may weigh the same it is a very different engine than an 85hp. Boat will be overpowered but if used with prudence would be fine. I have run 16'7" hulls with 135-140hp v-4's and they are stable until around 50 mph after that a handful. What you are not going to like is the gas consumption, the 76 engine probably is manual trim too. The early OMC v-4's had high compression heads and really should be run on premium gas. A good running 70hp will get you to 35 mph and save a lot of fuel. Unless this 135hp seems to be your only option. I would hold out for a lighter 3 cylinder 70hp to come along or even a 85-90hp. There is plenty of them around and it seems better suited for your intended use. Brian
geordybass	posted 11-08-2009 09:24 PM ET (US) Thanks bris boats! The motor has power trim and tilt on it. Compression on it is 115-120 even. I will usually be running at under 40-MPH, and my guess is that lower RPM means less gas consumption. I won't really ever full throttle it as I'm scared of tipping. I will be usually just fishing around in the harbors and channel islands in California. Do you think it will suit my purposes or will I be dissapointed? I'm not really looking to race anyways, just have more power than I need just in case :-)
brisboats	posted 11-09-2009 10:38 AM ET (US) Sure it will suit your purposes. The motor will use less gas if you keep out of the throttle. Still not going to be as efficient as a smaller motor though. Trouble is that when driving around a hot rod it is hard to stay off the gas. The 135hp is just a souped up version of the 115 hp. The motor has higher compression heads (looks like yours has been lowered), bubbleback exhaust, intake stuffers, bigger carbs, different timing, etc. to make the 20hp gain. The horsepower is made in the upper rpm range so yes if you stay away from that upper rpms it will be much like driving around a lower horsepower engine. Sounds like you have already have made up your mind. If not ask the previous owner when the last time the thermostats were changed. That motor is a bear to do. Brian
Tohsgib	posted 11-09-2009 12:20 PM ET (US) I guarantee you will fetch more $$ from a 1994 40-HP Yamaha than a 34-year-old OMC. I would sell the Yamaha for at least a grand, maybe $1400 and look for a nice 60 to 90-HP. If you get a Yamaha, you can keep your rigging which is what I would try and find.
pcrussell50	posted 11-09-2009 03:45 PM ET (US) Nothing super constructive to add other than that I have a 1975 V4 135hp myself. It's on another boat, a light 16 footer with a performance hull that is designed for higher speeds. It has been very reliable over the year that I have owned it. Peter Santa Barbara, CA
geordybass	posted 11-09-2009 04:14 PM ET (US) The Yamaha engine's lower unit was shot. And my motor is a flatback so no bubble. I can control it though have been around boats a lot so I know the deal. Should I get a bigger gas tank? I have three 6-gallon tanks. Is that enough? And I like that motor more because as the RPM are lower at cruise I would think that it would be pretty much more fuel efficient than a 70-HP. Kinda comparing it to my old truck and new one. I get about 22mpg on my [2006] Tundra V8 and I used to get about 19 on my 2002' Tundra V6. Apples to oranges yes Thanks for bearing with me guys! And how fast is the max speed this motor will be pushing?
brisboats	posted 11-10-2009 05:31 PM ET (US) A hot 135hp should get in the low to mid 50's. But no such thing as a flat backed exhaust 135-HP. Looks like what you may have is a 115hp with a 135-HP cowl. Whichever motor it is, it is not going to be more efficient than a 70hp, even at cruise. A crossflow v-4 115hp or 135hp can go through those three 6 gallon tanks in an afternoon with relative ease. I would run an 18 gallon under my rps and an extra 6 gallon just in case when running one. Even a 2-3 hour easy afternoon cruise always burned off at least 12 gallons more often than not the 18 gallon tank was spent. The motor at idle is very thirsty too. Brian
pcrussell50	posted 11-10-2009 11:03 PM ET (US) My 1975 135hp V4 crossflow burned 10 gallons on a 30 mile round trip this past September. That was in a lightweight, 16 foot performance hull, bass boat-like proportions, running at 5,800-RPM most of the way, but throttled back, because the prop is not coarse enough for a lightweight boat. Just a data point for you. I'd have better mileage figures for you, but most of the time I run her for about 5 minutes, to our favorite cove, swim, sunbathe, fish, and then 5 minutes back to the dock, where I send the wife out to get the trailer and I make a couple of speed runs by myself. On those days, I only burn about a gallon and a half for the whole day. Peter Santa Barbara, CA
jimh	posted 11-11-2009 08:55 AM ET (US) The fuel efficiency of a motor, that is, its brake specific fuel consumption, generally is best when the motor is running with about two-thirds to three-quarter throttle and with at least 50-percent load. Running a more powerful motor at lower throttle and lighter loads generally results in worse fuel economy.
adlert	posted 11-11-2009 10:58 AM ET (US) To add to JimH's comment, cruising with a cross-flow engine such as the 135 hp will definitely not be as efficient as cruising the same speed with the more efficient loop scavanged 3 cylinder engine.
Tohsgib	posted 11-11-2009 11:36 AM ET (US) Get the model number. 135's should be bubbled.
pcrussell50	posted 11-11-2009 03:13 PM ET (US) Yes, Jim. My 3mpg with the v4 135 was at high rpm and light load under part throttle. If I had had the right prop, I could have run less rpm, more throttle opening, and higher load... putting me in a more efficient spot in "the envelope". FWIW, I agree with the others that if fuel consumption is an important criterion for the OP, he's better off with the smaller displacement motor with the appropriate power rating. That said, not all of us have that concern. My typical boating day consists of about 2-5 miles of distance covered so even my 135hp v4 at 3 mpg won't be putting me in the poor house. Peter Santa Barbara, CA
geordybass	posted 11-11-2009 03:46 PM ET (US) Hey, the model # is 135643... but the cowl says 90hp... I'm kinda confused but the model # is for a 1976 135hp Evinrude. Lets say the powerhead was 90 or 115 does that maybe decrease the fuel consumption?
brisboats	posted 11-11-2009 05:16 PM ET (US) Simple answer is yes but not much. The 135's have the "tight" heads resulting in higher compression numbers than you posted. Higher compression engines are generally more efficient. 135's also are able to flow more exhaust through the bubbleback exhaust housing. It looks like you have a 135 midsection with a different power head, likely a 115hp. Not a huge difference in gas consumption between the two but no where near where you would be with a loop scavenged 3 cylinder 70hp as myself and another poster have said. Looks like you own it already so bolt it on and post some numbers. A good running 90hp or 115hp with power trim on that hull will provide plenty of speed. Brian
pcrussell50	posted 11-13-2009 04:05 PM ET (US) brisboats sez: quote: The 135hp is just a souped up version of the 115 hp. The motor has higher compression heads (looks like yours has been lowered), bubbleback exhaust, intake stuffers, bigger carbs, different timing, etc. to make the 20hp gain. The horsepower is made in the upper rpm range so yes if you stay away from that upper rpms it will be much like driving around a lower horsepower engine. I have had a '75 135 v4 xflow for a year now and have been delighted with it. So much so, that I've pretty much taken it for granted, but now reading these threads, I'm starting to learn about it. I now know what the "bubbleback" is. I also didn't know about the high compression heads. Do you think 91 pump is enough octane? That's what I've been using, but I can start to mix some 100-113 octane race fuel in there if 91 is too sketchy. Also, what are "intake stuffers"? Peter Santa Barbara, CA
brisboats	posted 11-14-2009 11:10 AM ET (US) Peter, The OMC 135hp is not a motor to take for granted. On a Montauk hull it is faster than the coveted mercury prop rated 115hp inline six that gets a lot of press here. The early motors like yours were made to run with the better gasoline of the time. Later OMC lowered compression and even had thicker head gaskets to use the poorer quality fuel of the mid 1980's. If it were my motor, I would want to run 92 octane or higher and make sure the timing was set at 25-26 degrees not the 28 some motors called for. Crossflows are prone to coking the rings so it is imperative that the timing and gas be right. Do a compression test on your motor too as it may have had the heads or gaskets changed out to run on regular pump gas. Intake stuffers are simply intake filler blocks used to create better airflow. OMC used them to create more horsepower on the 135's and 140's. The 140hp came along in 1977 I believe and used an additional modification to the lower exhaust web between the two bottom cylinders to attain the extra 5hp. This cut can be easily made if the engine is apart. The 140's also used diverters in the cylinder heads to redirect the water flow not for better cooling. I am not sure if the 135's had those. At any rate this is a case where the factory took a 115hp motor and added a few well thought out modifications to achieve the extra reliable 20hp. The 135's were factory hotrodded 115's, the higher compression and unlimited powerpack creates a crisp revving motor that will turn 6000 rpms or more and still stay together for a long time. The bubble back exhaust is machined to match the block and creates a much better flow, many would argue that most of the horsepower gain is attained by the bubbleback. Hope you enjoy yours and it continues to provide thrilling and reliable service. Brian
pcrussell50	posted 11-14-2009 04:05 PM ET (US) Now THAT was a hell of a good answer. Thanks. Funny. Way back before I bought this motor, the previous owner started it up on the muffs while he was demonstrating it to me. It recall thinking how raspy and crackly it sounded. I am an amateur auto racer and and I build my own race engines to help defray costs I recall thinking when I first heard that 135 how it sounded like a high compression motor... that was was waaay before I actually knew that it was. Peter Santa Barbara, CA
L H G	posted 11-15-2009 02:55 PM ET (US) Brian, your statement caught my eye. On the 1974 Evinrude 135, powerhead rated at 135HP, what would be the prop HP? I have been told the later Merc 115 Towers were actually putting out 125 at the prop. I find it hard to believe the old OMC 135 did any more than that. I ran a 1973 powerhead rated Merc 150 Tower on my 1971 Nauset for 11 years. A screamer! With any of these engines of this power, I think a stand up console configuration in an old 16 is mandatory for safe WOT operation. From my experience with the Merc 150, I would not want to be sitting down.
brisboats	posted 11-15-2009 07:11 PM ET (US) Peter, Your welcome. Please do a compression test and let me know where it is. The last 135hp I had I sold to a nice member here and it tested 150psi on all four with my mac gauge. Wow! Crisp and raspy to say the least. Larry, I have never dyno'd one but would guess you are right probably around 115-125hp same as the adi inline sixes like yours. Where the V-4 wins in my opinion is torque and there is even more potential remaining inside the motor from a tuning perspective. The 1985-1988 adi inline sixes had already achieved all Mercury could do with that motor. Power to weight the Mercury wins and on a lighter hull might even be faster. Didn't you once say that your Nauset with the 150hp was no match for the OMC 135's of the day? ;-). Yes, definitely no sitting down with either motor. Brian