Hey fishing geeks!...Can I use my Mercruiser 350 mag MPI to troll?
 

I have a 21' Chaparral that I want to occasionally use for fishing some of the big lakes up here in central BC. I have adapted a downrigger on the starboard side and will surface troll with another rod on the port side. With the engine at idle I can maintain a trolling speed of about 2.5-2.8 mph. Is it "safe" to run that engine at idle for 1.5-2 hrs? I've looked into installing a true trolling motor but that would involve some major "drilling and schit" on the hull which I don't want to do.

What say yee PPOT fishermen / boat engine specialists?

I'm no specialist, but here in Oregon I've seen most with smaller trolling motors. Well, all, thinking about it. Sorry,

likely depends on the water pump in the out drive

most are sized to flow the water to cool the motor at higher speeds
and not over cool the motor at those speeds
so may not flow enough at idle speed for extended time

watch the temps and take it out of gear and rev a bit to drop temps
or use a el or small gas ob to troll

I'm 46, been fishing for 42 years, only twice from a boat, both times an aluminum jon boat with an electric trolling motor....

On all occasions the temp has always been in the ideal range so I'm not too worried about that. My main concern is will I lay some serious carbon on the rings and plugs over time and cause some premature wear? You wouldn't think so with an EFI engine compared to an old carb one. I'm just trying to see if others here have done what I'm doing and what their experience has been....but thanks for the heads up!

Another idea just to toss out. A sea drogue/sea anchor/drift sock. It would allow you to put the rpms up higher. But it is more gear hanging off the stern to tangle stuff in. I've seen folks even dragging a bucket with hole cut in the back.-WW

ps. The biggest downside is the potential to wrap it into the screw. I used floating poly line and a couple of chunks of foam to hold the line so it floats and doesn't sink near my screws. Almost every boat the CG tows in from offshore has a drogue off the back so it won't ride up over the tow line.

My dad fishes on the open ocean 4 months out of the year. I asked him. He said an inboard should be able to troll like that, but the cooling system needs to be correct. He said there are boats that will overheat because the cooling impeller is not pulling in enough water. In that case you can run the engine at higher speed, and pull drag bags to slow you down. Not the most fuel efficient option.....

He runs a Honda outboard, makes about 150hp.

Have you tried it yet to check the speed?

I did this for years in an 21' SeaRay with a 175hp 2-stoke Mercury outboard. I never had any issues with overheating. The biggest problem was maintaining a slow enough speed for freshwater trolling with downriggers. It was OK for Rapala's and flashers, but not down-rigging. I fabricated a flat plate that hinged down behind the propeller. Now you can buy them for most outboards.

Of course the best option is a little kicker for trolling, but I understand not wanting to drill the transom.

Your motor will be fine as long as you have a good impeller and thermostat. I have trolled for up to 8 hrs at various rpms. Well slow troll form 1.5 mph thru 20 mph depending what we are fishing for. If you need to slow the boat down you can do it several ways, a cheap way is to cleat some 5 gallon buckets and drag them behind the boat, or trim the motor up so the prop doesn't bite so much. Good luck!

You should ask this question in the PARF forum. It is full of trolling experts over there!
Other than than that, I do not know.

I had a Chaparral Signature 290 and considered installing one of these for a small outboard in case I ever needed to limp home. I had twin Volvo's and decided I'd probably never need it. I'd rather drill the swim platform instead of the transom....

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