1976 MERC 350 35hp twin - more power?

[jaykup]

It's on a 15 foot fiberglass cathedral/multi hull fishing boat. The boat used to do 20mph according to a GPS at top speed in smooth water. It stopped pumping water through the engine, don't think its clogged, maybe a bad impeller. Now it only does 13mph or so, and I'm guessing I toasted the motor.

I'd like to tear it apart, bore it a size over and get some new pistons for it, is there anything I can do to this motor while I'm in there (porting, bigger carbs, different reed cage, etc) to give it 10hp or more?

 

[Chinewalker]

Re: 1976 MERC 350 35hp twin - more power?

For starters, you'll need to confirm the year of your motor, as the 35 was made in the 1960s, and again in the mid-late 1980s.

As far as "hopping up" your motor, you're not likely to gain much. Your boat is a heavy older boat and any mods you make would likely not be noticed, and may in fact hurt performance. You may find that a rebuilt motor will perform better than what you had been getting previously, simply because it is freshened up. If you really want more speed, save your money and get a larger motor.

 

[sschefer]

Re: 1976 MERC 350 35hp twin - more power?

For starters, you'll need to confirm the year of your motor, as the 35 was made in the 1960s, and again in the mid-late 1980s.

As far as "hopping up" your motor, you're not likely to gain much. Your boat is a heavy older boat and any mods you make would likely not be noticed, and may in fact hurt performance. You may find that a rebuilt motor will perform better than what you had been getting previously, simply because it is freshened up. If you really want more speed, save your money and get a larger motor.

Perfect answer!!

 

[jaykup]

Re: 1976 MERC 350 35hp twin - more power?

]For starters, you'll need to confirm the year of your motor[/B], as the 35 was made in the 1960s, and again in the mid-late 1980s.

As far as "hopping up" your motor, you're not likely to gain much. Your boat is a heavy older boat and any mods you make would likely not be noticed, and may in fact hurt performance. You may find that a rebuilt motor will perform better than what you had been getting previously, simply because it is freshened up. If you really want more speed, save your money and get a larger motor.

Thanks for the great reply. I only paid $1000 for the boat, motor and trailer. Most used motors seem to go for $750-$1000 in the hp range I'm looking for. Rebuilding seems like the best bet, when I did 2-stroke dirt bikes, it was usually around 100 a piston, with another 100 in boring/gaskets.

I've attached some pictures of the motor to help determine year. Let me know if there are any modifications I can do with this year, maybe even a carb swap would help a bit? Sounds like there aren't any, but here is to hoping!

 

[sschefer]

Re: 1976 MERC 350 35hp twin - more power?

Sounds like you didn't like the recommendations given. That's O.K.

This is a two stroke motor. If you modify it for increased hp you are specializing the motor to operate in a smaller range of usability.. You might get better bottom end, better mid range or better top end and some times a combination of two but never all three.

It can also take its toll on reliability since the operating range will be modified. You may find that it is heavily loaded in an RPM range that you commonly want to run in. This will increase wear on the engine.

Think seriously about what your asking from the motor. It's been around a long time for a reason.