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| inconsistent RPMs https://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=11796 |
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| Author: | fishin4winns [ Fri Jun 14, 2013 11:11 pm ] |
| Post subject: | inconsistent RPMs |
Other than my tin can with a 15 horse johnson, I am new to boating and I am not familiar with the the larger boating world yet. Anyways, I just bought a 1985 horizon 170 with the 4.3L 185hp Merc. The first few times I took the boat out were very short runs just to see what it had. I see that the manufacturers rpms are 4400-4800. I was running a maximum of 4000rpms@ 43mph on gps. Once I had a day to spend more time on it, I have found that I lose rpms after it warms up good. When I first start it up, it takes some throttle and about a minute of warm up time before the R's come up and then I can back all the way off of the throttle to let it idle at a little over 500rpms. All seems well, I take off and get 4000 rpms for a while, but as soon as I back off of full throttle and get back on it, I can only achieve 3500rpms. The motor sounds like it is running good, but it won't pull the R's that it was. It feels like I took off without pulling the anchor. It goes, and the engine sounds good, it just doesn't reach max r's. I did put a hydrofoil on it just recently, but I refuse to believe that has anything to do with this condition. The engine does not run erratically, it sounds good , just not pulling the r's it should, or starts out with. My prop is an aluminum, 13 3/4 x 21. I'm sure I could take it to the local marina and they would fix me right up, but I threw the whole bank at getting this boat and I have plans for a 2g trolling motor so I'm looking to you guys for input. Has anyone had these symptoms before? Can you point me right to the culprit, or do I have to get off of my cheap a** and take it in? |
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| Author: | Walt [ Sat Jun 15, 2013 12:00 pm ] |
| Post subject: | Re: inconsistent RPMs |
Start with the basics... Fuel Filter, clean the air cleaner, new plugs, wires, cap, and rotor. If that doesn't do it, then get back to us. |
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| Author: | TX H210SS [ Sat Jun 15, 2013 1:46 pm ] |
| Post subject: | Re: inconsistent RPMs |
Are you trimming lower unit up a little once you are on plane. |
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| Author: | deafwish [ Sat Jun 15, 2013 6:55 pm ] |
| Post subject: | Re: inconsistent RPMs |
Start with Walt's suggestions & also consider a carb' rebuild - if it hasn't already recently been done. |
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| Author: | fishin4winns [ Sun Jun 16, 2013 10:51 pm ] |
| Post subject: | Re: inconsistent RPMs |
Thanks for the replies guys. The marina I bought it from, which claims to have done all of the service work since it was new, said that they put new plugs, wires, cap, and ignition in it last year, and they have also winterized it every-year. I checked the oil in the motor and the out-drive and that looks like new. I bought a new fuel filter, but have not had a chance to work on in yet, because I have been at the NASCAR races in Michigan all weekend. I will fallow up with some of the other suggestions and get back with the results. Once again, thanks for the replies. |
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| Author: | fiznuka [ Mon Jun 17, 2013 8:29 pm ] |
| Post subject: | Re: inconsistent RPMs |
If carbureted check your choke plate maybe it's sticking closed. |
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