Outboard motor

Hi all,

I preface this by saying I am admittedly a non-mechanic! I have a 200hp 4 stroke Merc Verado that I use heavily. I bring it in each fall for winterization, oil filter, oil change, etc, but that’s really the extent of my maintenance, other than a can of sea foam each time I fill it up. My motor has run fine this summer, but I feel like my max speed is down about 5-7 mph from where it has been in the past, and my hole-shot takes a bit longer. I had 3 buddies in my boat last weekend and it really took me a long time to plane out. They are big guys, but I figured my 200 hp should handle it on a 19 ft aluminum Lund better than it did. Prop is the same. Also, when I start it, I can smell exhaust if I idle? That sounds really dumb I know, but I hadn’t noticed that before. It doesn’t sound any different. My smart gauges say everything looks OK.

Would you recommend one of those fuel additives like Quickleen or StarTron, or is the Sea Foam enough? I’m loathe to pull it off the lift and bring it in when I feel like it runs well, but not like it was. That being said, I don’t want to neglect something, if ANYTHING I’m saying makes any sense to you guys!

Thanks

I’m far from an outboard mechanic to, but I think a can of seafoam every time you fill it is way too much. Even if you have a 30 gallon tank.

Not that I’m saying it that’s your issue though.

I can’t help there but why are you adding a can of sea-foam with every tank? Especially if you use it heavily?

No additive is going to get back the 5-7 mph you’ve lost.

The Sea Foam you’re adding is definitely a heavy dose but I’m sure if has nothing to do with your lost speed.

The first thing I’d look at would be the prop. Any recollection of hitting anything, even something minor? I would start with a close inspection of each blade and if possible I’d borrow a prop of the same diameter and pitch from a buddy for a quick rip just to rule that out as the cause of your issue.

Thanks for the fast replies. I’ll back off the sea foam. I’ve looked at the prop. No nicks. I haven’t taken it off – if I had wound up a bunch of line on it could that do it? I don’t see any but again that’s just an external inspection.

Appreciate it guys.

Are the rpms down also?

RPM’s seem to be the same. I noticed the speed issue when in a fishing tournament and going all out to our first spot, and getting passed by smaller boats. I still get 39-40 mph maxed out but was mid 40s.

If the rpm’s are the same and the mph isn’t, then the prop is slipping more. Is the motor trimmed to where it should be? Weight of the boat change? Water logged transom? Hub worn out and slipping? A lot of things it could be.

This may sound crazy but I have seen it around here with the lake water we have that is so fertile it will cause aggressive algae growth on the hull when they sit more than a week in the water.
When was the last time the hull was scrubbed and waxed?

I have witnessed this causing a 10 MPH drop in speed and hole shots are terrible.

How much Sea Foam should we be using? I put probably too much in my boat, pontoon and jet skis. I didn’t know that a can a tank is too much….what is the right amount? Jet skis are 2 stroke others are 4 stroke.

thanks

One ounce per gallon.

http://www.seafoamworks.com/how2instructions/

-J.

MN Z wrote:

How much Sea Foam should we be using? I put probably too much in my boat, pontoon and jet skis. I didn’t know that a can a tank is too much….what is the right amount? Jet skis are 2 stroke others are 4 stroke.

thanks

I believe there are recommendation on the can as to how much to add per gallon, should be same or similar to stabilizer. I personally do not run any additives in mine, just use nothing but non oxy fuel.

Possibly the prop hub going bad or a wad of fishing line packed inside?

Iowaboy1 wrote:

This may sound crazy but I have seen it around here with the lake water we have that is so fertile it will cause aggressive algae growth on the hull when they sit more than a week in the water.
When was the last time the hull was scrubbed and waxed?

I have witnessed this causing a 10 MPH drop in speed and hole shots are terrible.

X2 If a boat sits in the water all summer this can be an issue.

Also how much weight you add can really kill speed. 3 buddies with their gear is quite a bit more than you probably have typically.

I’m having the same issue with the Merc 115 on the Pontoon.
Ran perfectly then 2 weeks later when I got back up it went from 5900 rpms to 5000 rpms and 29 mph to 24 mph.

I leave it tied to the dock with the motor down.

Yep, Your hub slipping or water logged foam/wood

blackbay wrote:

If a boat sits in the water all summer this can be an issue

This is the key question right here. Does the boat sit in the water in a marina slip all summer?

If the answer is yes then you have a situation with either algea build up on the hull or you have some kind of leak that is water logging foam or wood in the hull.

Otherwise as others have said the leading suspect would be a slipping hub in the prop. Take the prop to a prop shop.

Grouse

Guess What?
I took that Iowaboys recommendation and hit the poontoons with a 3M pad and sure $h!t it worked. Couldn’t believe it because there wasn’t that much algae on there.

Bonus – I got a nice case of swimmers itch that I’m dealing with now.

Hub replacement is easy and cheap, even if you’re not a big DIY’er. As mentioned above, if RPM’s are the same but speed isn’t you’ve just ruled out everything above the gear case. Hub would be cheapest/ simplest first shot at fixing.

I wouldn’t think it would be a slipping hub on a Merc as I am using a Merc Bravo prop on my Yamaha, and the hub is a squarish piece of plastic. I would think if you have that type of hub, there is no way for it to slip. Boy, you guys that use Sea foam, have to use a lot of it. The Stabil Marine that I use is 1/2 oz for 5 gal. Marine Stabil has worked great for me. Even used it when I had a winter house on the Gulf for 5 years that my bay boat sat unused on a lift over the water, for 6-8 months at a time. Engine always ran great, but I also only used non ethanol gas.

Musky Ed wrote:

I wouldn’t think it would be a slipping hub on a Merc as I am using a Merc Bravo prop on my Yamaha, and the hub is a squarish piece of plastic. I would think if you have that type of hub, there is no way for it to slip. Boy, you guys that use Sea foam, have to use a lot of it. The Stabil Marine that I use is 1/2 oz for 5 gal. Marine Stabil has worked great for me. Even used it when I had a winter house on the Gulf for 5 years that my bay boat sat unused on a lift over the water, for 6-8 months at a time. Engine always ran great, but I also only used non ethanol gas.

I have a Merc prop with the square plastic hub on an F150 Yamaha. In 13 years I have worn out 2 hubs. I replaced the second one just last month. Never a definite strike I could say caused it either time. This last time something just felt different on a couple fishing days but it started slipping badly while pulling tubes.

What are you hitting for max rpms trimmed up at WOT?

What prop are you running?

Did you run a similar load last year with better results?

What plugs are you running in your prop?

A buddy of mine was having similar issues with his L4 Verado this spring. Except his was a bigger change than what you describe.

The dealer couldn’t get him in right away, so he changed spark plugs, fuel filters, all of the pencil coils etc, with no change in performance.

Once he brought it to the dealer they said it was the wrong prop…..he explained to them last year the same prop was amazing with it’s hole shot.

Turns out it was just a loose clamp for the super charger. The leak wasn’t allowing the normal amount of boost.