Good morning!

*please note: novice boat owner her*

Have a quick question on the performance of my new(used boat). Purchased a "new to me" boat last weekend in the Dalas area and took it out the same day. Boat worked great and was very happy with the purchase. Took it out the second day to Ray Hubbard and it ran great for about 3 hours...then the engine would not kick-it into the next level to get on the plane. A little frustrated but was hoping it wasn't a big deal since I had not even owned the boat for 24 hours yet. Went to my buddies house and we hooked up the cups to get a closer look..and waaaahla the engine was working fine again, no response problems. So I chalked that one up as a (?). Went out again yesterday to Somerville and same story..motor works great for a couple of hours then just won't "get up" anymore. Now, I did make a obersavation! Me being a VERY new and novice boat owner... Both times this has happened I think? was right after the boat was humming and I pulled the throttle back pretty hard for whatever reason. Of course after stoping abroptly the whole back of the boat got slammed with my own wake. Could this be the reason?..and if so do I need to be worried about possible damage that I've done to the motor? Anysight you can provide would be greatly appreciated! In addition, do any of you guys know of a honest marine tech in the Houston Area? Regardless of what is currently going on I figure it would be good to let a mechanic give it a once over.

OH BTW its an 85 Skeeter Strada 15'6 / 70HP Johnson

Thanks again!
-Srohde

My first, and only guess is cavitation. It's possible you created some kind of air pocket and the prop was spinning but not biting into the water.

Well now that I think of it, a second guess would be the prop hub slipping. If your prop has one, it is a rubber piece inside the prop that is designed to slip if you over torque the prop, (by hitting something), so you don't damage your shaft and gears. If you can slowly increase throttle and get going but when you nail it, you don't get up to speed, it could be the hub slipping. James propeller in Carollton has a bench top torque tester that can tell you if it's good or not. And of couse, they can repair it also.

i second the hub slipping, as the motor/lowerunit gets warm it might start slipping. you should be able to tell pretty easy if thats it, watch your RPMs and see if you are getting the same RPMs when your gassing it but not moving well. Also make sure you dont over rev it. which you can do fairly easy if the hub is slipping.

Thanks for the info, I'll check when I get home from work. However let me give a little more detail...see if it helps.

When boat is working properly the boat will accelerate quickly when the throttle is around 3/4 the way down. When the boat is not working properly I can put the throttle arm all the way down and I have the same RPM's as about 1/2-3/4 Arm.

When you say you get slammed by your wash, did you take on a large amount of water? If you add a couple hundred pounds of water weight to the boat, your not going to get the same acceleration.

I guess I was using the word "slammed" pretty loosly, water did go over the top of the motor shroud, but was not excessive in the boat. Very little water below. The only reason I was questioning this was to know if water is getting through the shroud and getting into the motor....

That is extremely unlikely. Well let me rephrase.

It is possible that water may penetrate past the shroud gasket however, it is highly unlikely that it could get past the air-box and make it into the intake.

It could be more along the lines of the fuel tank being contaminated with particulate matter and as you slosh around or come to an abrupt stop, it could cause the fuel intake screen to clog up.

If you turn the motor off and restart it will it continue with the described problem?

One more suggestion, if you don't have your boat in the water and under a load, don't rev your motor over 2000 rpms. Just in case you didn't know. I wouldn't want you to damage the powerhead trying to diagnose it in your driveway and rap the motor out.

Sounds like the motor loses power when its hot. May be a compression problem(ready for a rebuild). Can check compression after warm up then again when it has run "a couple of hours" to verify. Don't believe you've damaged the motor by chopping the throttle hard.

Unfortunately, yes when I turn off the motor and re-start the problem still persists. However, and I'll check when I get home, last weekend after the motor being off for 2 hours the problems did not seem to be there.

Thanks for all the helful tips guys.

Just for grins, are you trimming the motor properly? If it is trimmed too high, bad things can happen. Proper motor trim is often a challenge for new boat owners. Also, trimming the motor as you operate the boat is an ongoing process. Proper trim angle is dependent on boat speed/conditions and vice versa.

Thanks for the info HasBeen..fortunately I got a nice "trim 101" from a buddy. If not for that this would definately be a potential problem.

Are you taking on water? Runs good for about 3 hours or so...takes on some water...gets heavy in the back end...bogs down. I had this happen to me. Turned out to be a leak in the livewell hose.
When you pull your plug out after a trip, does it drain any water? If so, that could be your issue. Try plugging off everything next time you go out.

my money is on compression loss. defiantly get it checked out by a decent mechanic before you take it out again - or you may be rowing back. in fact, i'd have him completely service the motor - tuneup, lube, etc. it'll be money well spent. The real lesson here is to have a boat checked out first before buying.

Update: First off thanks for all the input. I finally buckled down on Wed. and took it in. Found a pretty reputable guy in the Houston area that came recommended from a friend. After talking with him he pretty much mirrored what you guys were saying; in short that since I have know real idea when the last time the boat was serviced that I should probably start from scratch and get the engine fully serviced to get some sort of baseline. His first guess was clogged carbs etc...and after replacing the carb kits he found a lot of trash in there so that very well could have been it. Fortunately everything else seemed fine (surprisingly good compression ratios) although I ended up getting some service done on the lower unit. I'm picking it up in an hour and am hoping that it will purr on the lake this weekend. Thanks again for the info....I'm sure I will be asking quite a bit more questions.

Is it Friday yet?