Boat Slower At Same RPMs?-gctid817191

[Guest]

We noticed on our last time out thatwe were moving slower at the same RPMs. We have always been a 7 knot boat at 1800 RPMs. Taking into consideration the prevailing currents with or against us, if there is little or no current, we go 7 knots at 1800 RPMs.

So, what could be the reason why we suddenly have to apply 2200 RPMs to still attain 7 knots?

[mmichellich]

Is there new bottom growth? Do you see an engine smoking now that was not before? Are you towing a crab pot or something?

[mister_larry]

Interesting question: why is it taking about 20% more power to maintain your cruising speed?

Without getting into great, mechanical questions, the bottom growth dilemma is quite common. In both salt and fresh water the boat can pick up growth below the water line. Then there is a trim tab question. Could someone have mistakenly pushed the button and moved the tabs into a more downward position? Next in line (without hauling the boat) is an engine analysis. Are all cylinders operating? Is something blocking the air intake into the engine compartment?

Finally, and no one hopes, that you have an underwater running gear issue.

[smitty477]

mmichellich has the answer - it is either growth on the hull or growth on the running gear and likely both.

It cannot be the engine(s) if the rpm on the shafts are increased to 2200 to attain the same speed.

[floatyerboat]

I was also thinking trim tabs. They may be stuck or in the down position and the system isn't working at all. If you cant see thru the water you can take a broomstick or something to see if they are working properly.

Gas? Diesels?

If gas I wanted to add I just installed electronic ignition and with problems very similar to yours, they've vanished and I have speed I've never had in three years.

It wouldn't hurt to check your transmission fluid also.

[yachtman]

When I bought my bayliner 32ft conquest it would only do about 5- 8 mph tops. I pulled it out cleaned the bottom and immediately got 32 mph.

Cleaned up and all was good.


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[Pat_Careen]

Are both of your transmissions engaging? Maybe shifter cable issue? 2200 rpm is about right for one engine at 7kts.

[Guest]

Thank you all who sent replies. All were useful responses and I will keep those things in mind in the future. However, the solution turned out to be New bottom paint. We had serious growth on the ottom and we're overdue for new paint. Also had a lot of mussel growth that hadn't been caught by our divers. Thanks all.

[Centerline2]

"mguelker53" post=822049 wrote:
had a lot of mussel growth that hadn't been caught by our divers. Thanks all.

paying someone to do something they arent doing?... I would be finding a different company to do the BWL maintenance....

[jas0381]

I suspect you were being kind about the divers missing mussels.?!