High speed motoring change

[Macsailing]

Ok 26m experts, i need some help

My 2010 26m with suzuki 70hp will now only go about 16mph, 2 adults, ballast empty, rudders and centerboard up, 5800 rpm and rev limiter comes on.

I could usually get 22 mph in same conditions...i cant figure out what has changed? It used to feel smooth, just flying accross the water, now it feels heavy and labored like im pushing a barge.

Motor seems to spin up to limit fine and smooth, prop is not slipping, ballast is empty. I know tides, currents, head wind and chop will slow the boat down significantly, but im boating in the same area as before.

Yesterday i did about 16 miles, fighting waves and chop in the ocean, i could only get 13 mph with ballast full and burned 10 gallons of gas. When i got into san diego bay i emtied the ballast but could only get to 15.3 mph and boat was hsrd to steer moving right to left a lot.

I have added weight to the boat with gear, maybe 200 lbs.

What do you think?

1. Im pretty sure motor is trimming all the way down

2. Weight seems to be evenly distributed.

3. Engine rpm is 5800.

[Be Free]

Is hitting the rev limiter a new thing?

Reduced speed along with left-right wandering could be a partially lowered centerboard.

My first guess though would be a slipping hub on the prop.

[Macsailing]

Interesting. That would definitely explain the issue. How do you check for slipping hub?

[Macsailing]

Its a solas prop with an rbx-150b hub kit.

I think its a rubber mount pressed in to the prop, maybe it is slipping at high rpm?

[Macsailing]

Yes, Hitting rev limiter is a new thing.

[mkstocks]

I second the 'slipping hub' theory. I had the same symptoms on an old Johnson outboard after my prop struck a submerged tire. I sent the prop in to be rebuilt, and it came back several days later. Symptoms were gone after reinstalling.

I do not know about how to check whether the prop is slipping, other than by observing the same symptoms that you describe. If you try this fix, the worst case is that you end up with a reconditioned prop.

[Macsailing]

Not pressed in, hub slides in and is interchangeable.

[Be Free]

New rev limiter problem and low speed points very hard at a slipping hub.

Obviously all of the following is with the engine off and preferably boat on the trailer.

Lift the engine and put it in gear. Does not matter which gear.

Try to turn the prop with your hand.

If the hub is slipping you will be able to turn the prop by hand and the engine will not be rotating.

I don't think that you will be able to turn the engine over by turning the prop but if you do it will be very hard and you will feel the pistons compressing and releasing as you do.

[Macsailing]

Thank you. I will remove prop and replace RUBEX hub and check torque. Boat is in the water so have to do it from a dingy.

I think you are correct though, must be prop hub slipping at high RPM.

Maybe it just needs to be torqued down.

[Jimmyt]

If it’s made like the etec, torque doesn’t matter as far as prop slippage is concerned. The rubber hub has a splined core that mates to the splined shaft. When your prop slips, it’s between the hub and the prop, not the shaft and hub.

And, you may not be able to cause slippage by hand (unless you are capable of producing 40-60hp with your hands).

If the boat has been in salt or brackish water, removal of the prop and hub can be a real treat.

viewtopic.php?p=354488#p354488

[Outlander]

Ok 26m experts, i need some help

My 2010 26m with suzuki 70hp will now only go about 16mph,

I have a 2008 Suzuki 70hp on my 26M, 16mph has always been my max speed.

[Be Free]

Since it's been a while since the OP posted I'll engage in a little thread drift with you.

If we take the OP's word that he used to get 22 mph and only gets 16 now and if we take my word that I have no problem getting to 16 mph with my 40hp Honda then it appears that we should look for what is different on your boat.

Things to consider: (my answers)

Is your measurement with or without ballast? (without ballast)
How heavy is your boat (gear, fuel, crew, etc) under test conditions? (very heavy, 20+ gallons, only me, large house bank - 250lbs)
Fresh or salt water? (usually salt, slightly slower in fresh)
Sea state (wind, waves, currents)? (smooth to light chop)
How would you describe the condition of your engine? (excellent)
Is the bottom clean and smooth? (clean but not smooth, needs new bottom paint)
Any mods topside that would increase wind resistance? (no)

[dlandersson]

Also:

Do any of the crew eat too many Krispy creme donuts?

[Macsailing]

Folks, so sorry for the delay, out boating.

I really appreciate all the responses and advice.

I did solve the problem...propeller was slipping at Rpm over about 3500. I replaced the Solas propeller and Solas RUBEX removable hub and boat was immediately back to normal.

Now it glides over the water smooth, and i can hit 5800 RPM, but not the rev limiter.

With boat very full, fishing gear, water, food, extra battery, 100lbs of chain etc

15 mph at 4400 rpm ballast empty
18.3 mph at 5300 rpm ballast empty
22 mph at 5800 rpm ballast empty

I did a 50 mile trip off san diego, 8 miles at 4 mph trolling speed and about 42 at 14 to 15 mph in rough ocean water and burned 13.2 gallons of fuel.

I finally got the RUBEX hub out of the old prop (10 hours on prop and hub kit) by freezing it for two hours the pounding it out, definitly slipping as the square edges were rounded and it was in twisted.

Gonna get with solas and find out happened.

[NiceAft]

and about 42 at 14 to 15 mph in rough ocean water

I sure hope the ballast was full; you didn’t say.