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Seeking advice on replacing engine

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DSherwood
Deckhand

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USA
8 Posts

Initially Posted - 09/05/2016 : 08:54:51

I am a fairly new sailor and new owner of a 1984 Catalina 25. The 1984 Johnson SeaMaster 9.9 that came with the boat is unreliable. I'm considering getting a different engine, possibly as backup while the old engine is being serviced, or possibly as a replacement. What are some options, and what are potential mistakes? Would an 8 HP, 4-stroke, long-shaft motor be OK? One dealer said the SeaMaster and it's prop develop a lot of torque. Is torque a function of the propeller specs? How important is that? Thanks. Duane, Burlington VT

DES

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 09/05/2016 : 09:24:16

Welcome Duane! You're on a pretty big lake, so I'd day the first requirement is what most call an "extra-long" (XL) shaft, which is about 5" longer than the "long" shaft. That helps keep the prop in the water when the 25' boat pitches fore-and-aft. Not all small outboards offer that option, but Honda, Tohatsu and Yamaha do on some models. Tohatsu is about the lightest for its size among those (including Mercury). Honda and Yamaha offer what's generally called "high thrust" options that have larger, lower-pitched props specifically designed for pushing and stopping heavy boats rather than making small boats go fast. Honda also diverts the exhaust in reverse so it isn't sucked in around the prop where it reduces thrust.

When I bought a new Honda in 2003, a factory rep told me the 8 is the very same product as the 9.9 except for the cam, which was set up for more torque at lower RPMs, while the 9.9 (obviously) has more HP, but at wide-open throttle. On these motors, just a little over half throttle gets you close to the maximum speed the hull will go without planing, which of course they can't do, so more throttle mostly just wastes fuel and makes noise. The 8 was a few hundred $$ less than the 9.9. I really liked it, and another guy here, "Voyager" Bruce Ross, the current owner of the boat, still has it. It has more than ample power for that boat, even against strong winds and big chop. And the 4-stroke is smooth, quiet, smokeless, and starts with a touch of the electric start button.

Others here like their Tohatsus, Mercurys, Yamahas, etc... Some folks have 6hp motors and less then XL shafts, but I wouldn't recommend either for Champlain.

Regarding the term "torque", that's what really counts for developing "thrust" at lower RPMs, to push the boat or stop it (using reverse). It's the twisting force the engine can create. Thrust is basically the amount of water the prop can move in the desired direction (parallel to the prop shaft) to push or stop the boat. Just as important as torque is the pitch and size of the prop, which is sort of like selecting a gear ratio on a transmission where you can only have two--forward and reverse. The lower pitch will push the water in the desired direction better at lower boat speeds, but it should have more blade area to make efficient use of the engine's torque.

Another consideration is the dealer--will he set up and bench-test the motor for you and be available for parts and service later on... I considered that worth a few extra $$ over internet sources.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 09/05/2016 09:38:48

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 09/05/2016 : 09:47:46

Oh--and now two commercials:

1. Join the Association ($22/yr), which supports this forum for this great community of sailors--one of the best on the web, and...

2. Get to know Catalina Direct, a third-party supplier of parts and upgrades for these boats. They know there stuff and have some model-specific products you'll have a hard time finding anywhere else.

Again, welcome!

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

DSherwood
Deckhand

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USA
8 Posts

Response Posted - 09/05/2016 : 12:28:38

Thank you, Dave. I found the information very helpful. And I'm happy to support with membership.

DES

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 09/05/2016 : 12:47:07

Mr. Bristles comments are spot on. I'll be more direct. Purchase a Tohatsu/Nissan/Mercury 9.8hp XL shaft. They are all the same outboard manufactured by Tohatsu. The extra +/- $200 will be irrelevant later. I replaced my 1987 Mercury Sailmaster with a Tohatsu. If I had to do it again I would purchase the Mercury, same motor, with tiller mounted controls. And yeah, local service has it's benefits.

Davy J

2005 Gemini 105Mc
PO 1987 C25 #5509 SR/SK
Tampa Bay

panhead1948
Captain

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345 Posts

Response Posted - 09/05/2016 : 14:26:32

Well this year I had trouble with my 86 7.hp Honda. Bought an 8hp electric start Tohatsu love it

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 09/05/2016 : 15:30:17

Wow, So the Honda gave 30 yrs of service and you jump ship. You are a hard man to please!

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 09/05/2016 : 16:27:26

I don't care which you buy--Honda, Yamaha and Tohatsu/Merc are all good engines... I'll point out a few items that led me to pick the Honda 8 Power-Thrust XL shaft with electric start:

1. The shift lever is on the front of the cowl rather than the side. (Yamaha had it on the handle, which was also an attraction.)

2. The "Power Thrust" version (4 blade lower pitch) was designed for heavy displacement hull applications.

3. The alternator is about twice the output of the others--12 amps.

4. The Yamaha 9.9 High Thrust 4-stroke didn't have a pull-starter (for backup to the electric) and the Tohatsu/Mercury 4-stroke didn't exist.

5. The dealer was close by.

6. I have great respect for all Honda products. (They have built more internal combustion engines and for more applications than anybody else in the world--all of them 4-cycle.)

(Not that it's that relevant, but when I had my current boat built, I chose a Honda outboard that is based on the engine from the Honda Odyssey, Pilot, V6 Accord, and various Acura models. The USCG uses the same engine, and the local mechanic that maintains theirs says "they just can't break 'em!"--but they definitely broke some competitive products!)

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 09/05/2016 : 20:06:16

I had the 9.8 hp XL shaft and electric start outboard from Tohatsu/Nissan/Mercury under the Nissan label and was very happy with it. Twist grip throttle and the shifter was on the front of the engine, not the side.

DavidP
1975 C-22 SK #5459 "Shadowfax" Fleet 52
PO of 1984 C-25 SK/TR #4142 "Recess"
Percy Priest Yacht Club, Hamilton Creek Marina, Nashville, TN

DSherwood
Deckhand

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USA
8 Posts

Response Posted - 09/09/2016 : 06:31:14

Dave Bristle, regarding your first reply above, do I understand correctly that the 8 HP Honda develops more thrust at lower RPMs? Thanks, Duane

DES

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 09/09/2016 : 08:53:59

I'd say it can increase its thrust more quickly (forward or reverse) at lower RPMs than the 9.9. That's what torque is about. But the distinction is probably minor. The bottom line is it's at least as good on a C-25 as the 9.9 for a few fewer boat units--and maybe a little better. That's according to a corporate rep.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

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